How Do I Bypass Bad Gateway 502? The 18 Top Answers

It has happened many times to almost everyone that when we try to access a website, an encrypted message appears on the screen indicating that we cannot access the website. These error message codes are generally referred to as HTTP error codes. HTTP (HyperText Transfer Protocol) is a process through which the client interacts with the server. When accessing a web server, each HTTP request received from a server is answered with an HTTP status code consisting of 3 digits and divided into 5 different categories.

Series begins with code 1** Information 2** Success 3** Redirect 4** Client error 5** Server error

The series starts with 1**, 2** and 3** are fully functional requests and are discussed below.

The series starts with 4** and represents client-side errors, which are discussed below.

The series starting with 5** represents server-side errors and is discussed below.

Note: 4** and 5** are solvable by troubleshooting.

1** FYI, the HTTP status codes in this class are preliminary and are sent by the server before sending a full and complete second response.

100 – Proceed: This status code indicates that only part of the request was received by the server without problems and the client should continue the request or ignore the response if the request has already completed.

This status code indicates that only part of the request was received correctly by the server and the client should continue the request or ignore the response if the request has already completed. 101 – Switching Protocols: This status code is sent by the client in response to an Upgrade Request header and indicates the protocol to which the server is switching.

This status code is sent by the client in response to an upgrade request header and indicates the protocol to which the server is switching. 102 – Processing: This status code tells the client that the server has fully accepted the request but has not yet completed it.

2** Success: The HTTP status codes in this class indicate the successful completion of a request.

200 – Ok: This HTTP status code is a standard response for successful HTTP requests. The information returned with the response depends on the method used in the request, e.g. B.: GET or POST or HEAD or TRACE.

This HTTP status code is a standard response for successful HTTP requests. The information returned with the response depends on the method used in the request, e.g. B.: GET or POST or HEAD or TRACE. 201 – Created: This HTTP status code indicates that a new resource was created as a result of the successful completion of a request.

This HTTP status code indicates that a new resource was created as a result of the successful completion of a request. 202 – Accepted: This HTTP status code indicates that the request was received and accepted for processing, but may not be processed immediately.

This HTTP status code indicates that the request was received and accepted for processing, but may not be processed immediately. 203 – Non-Authoritative Information: This HTTP status code indicates that the request was received and understood and the information was sent back to the client because the response came from a third party and not the original server.

This HTTP status code indicates that the request was received and understood, and the information was sent back to the client because the response came from a third party and not the original server. 204 – No Content: This HTTP status code indicates that the server successfully processed the request but needs to return content or may not need to send any data back.

This HTTP status code indicates that the server successfully processed the request but needs to return content or may not need to send any data back. 205 – Reset Content: This HTTP status code is sent from the server to the client. It asks to reset the content from which the original document was sent.

This HTTP status code is sent from the server to the client. It asks to reset the content from which the original document was sent. 206 – Partial Content: This HTTP status code indicates that the server is sending only part of the requested resource due to a Range header sent by the client.

This HTTP status code indicates that the server is sending only part of the requested resource due to a Range header sent by the client. 207 – Multi-State: A multi-state response conveys information about multiple resources, following the message body with an XML message and containing separate response codes.

3** Redirect: The HTTP status codes in this class indicate that additional action is required on the client side to complete the request.

300 – Multiple Choices: This HTTP status code indicates multiple options for the resource from which the client should choose one. It could be used to represent different file format options or different media presentations for the same content.

This HTTP status code indicates several options for the resource from which the client should choose one. It could be used to represent different file format options or different media presentations for the same content. 301 – Moved Permanently: This HTTP status code indicates that the URL of the requested resource has been permanently changed to a new URL. The response should also include a new URL, and all future references to this resource should use the new URL.

This HTTP status code indicates that the URL of the requested resource has been permanently changed to a new URL. The response should also include a new URL, and all future references to this resource should use the new URL. 302 – Found: This HTTP status code indicates that the resource requested by the client has been temporarily moved to a new URL. The temporary URL should be specified in the Location field in the response.

This HTTP status code indicates that the resource requested by the client has been temporarily moved to a new URL. The temporary URL should be specified in the Location field in the response. 303 – See Other: This HTTP status code indicates that the answer/resources can be found at another URL using the GET method. When received in response to a POST/ PUT/ DELETE, the server should be assumed to have received the data and the redirect should be issued with a separate GET message.

This HTTP status code indicates that the response/resources can be found at a different URL using the GET method. When received in response to a POST/ PUT/ DELETE, the server should be assumed to have received the data and the redirect should be issued with a separate GET message. 304 – Not Modified: This HTTP status code is used for caching purposes. This means that the resource has not changed since the last request. Normally, when a document is cached, the date it was cached is saved. When the document is next viewed, the client asks the server if the document has changed. If not, then the client simply reloads the document from the cache.

This HTTP status code is used for caching purposes. This means that the resource has not changed since the last request. Normally, when a document is cached, the date it was cached is saved. When the document is next viewed, the client asks the server if the document has changed. If not, then the client simply reloads the document from the cache. 305 – Use Proxy: This HTTP status code indicates that the client’s requested resource can be reached through a proxy mentioned in the Location header. The address of the authorized representative must be given in the reply. Not all clients implement this for security reasons.

This HTTP status code indicates that the client’s requested resource can be reached through a proxy mentioned in the Location header. The address of the authorized representative must be given in the reply. Not all clients implement this for security reasons. 306 – Switch Proxy: This HTTP status code indicates that subsequent requests should use the specified proxy. But it is no longer used and is reserved for the future.

This HTTP status code indicates that subsequent requests should use the specified proxy. But it is no longer used and is reserved for the future. 307 – Temporary Redirect: Here the server sends the HTTP response to instruct the client to get the requested resource at a different URL using the same method used in the previous request.

4** Client Error: The HTTP status codes in this class indicate the errors that are technically due to a problem with the client’s request.

400 – Bad Request: This error code indicates that the HTTP request sent to the server has invalid syntax.

Troubleshooting Steps: Look for errors in the URL (Uniform Resource Locator), which is the most common reason. Cookies associated with this website may be corrupt. Therefore, delete the cookies and the cache of the browser. Try opening the same webpage in a separate web browser.

This error code indicates that the HTTP request sent to the server has invalid syntax. 401 – Unauthorized: This error code indicates that the user is attempting to access the resource without proper authentication. To require the user to provide credentials to view the protected resources.

Troubleshooting Steps: Check for errors in the URL first, if the URL is valid, then visit the main page and look for the Sign In or Secure Access link. Enter your credentials and try again, or if you don’t have valid credentials or forgot your password, follow the prompts to create a new account or reset your password. Clearing the browser cache can fix this error as invalid credentials may be stored locally in your browser i.e. H. interrupt the registration process. If the website does not require authorization, this error message may be an error. Therefore, it is best to contact the website administrator.

This error code indicates that the user is trying to access the resource without proper authentication. To require the user to provide credentials to view the protected resources. 403 – Forbidden: Generally occurs when the user has made a valid request, but the server refuses to serve it because it does not have permission to access the requested resource.

Client Troubleshooting Steps: Contact the ISP (Internet Service Provider) if the website works for others. In order to get permission, you need to speak to the site admin to grant access. If the user keeps getting this error, ensure that www data contains the correct permission to access file/read. Usually this means that the file’s permission should be set to read. Check .htaccess settings (.htaccess file controls access to resources specific to a certain range of IP addresses). It can also happen if your website doesn’t have an index file. If this is not the case, you should rename your homepage to index.html / index.php.

It generally occurs when the user has made a valid request, but the server refuses to serve it because it does not have permission to access the requested resource. 404 – Not Found: This error code indicates that the user can communicate with the server, but the server cannot find the requested resource/file.

Troubleshooting Steps: Check the URL again if it contains an error. Refresh your web page by pressing the F5 key. Clear your browser cache. Change the DNS (Domain Name System) server. (Only try if the whole site throws a 404 error.)

This error code indicates that the user can communicate with the server, but the server cannot find the requested resource/file.

5** Server Error: The HTTP status codes in this class indicate that the server knows it has encountered an error or is otherwise unable to complete the request.

500 – Internal Server Error: This is the most common server error and is usually referred to as a catch-all-code error. This HTTP error code indicates that something is wrong with the website server and the server cannot identify the exact problem. While this is not a client-side issue, the client can try to resolve it with the following steps.

Client Troubleshooting Steps: There may be high web traffic. Reloading the web page by pressing the F5 key may fix the issue. Clear your cookies and your web browser cache. Check your website’s .htaccess file. Make sure it’s built correctly. Check if there are incorrect permissions on files and folders.

This is the most common server error and is usually presented as . This HTTP error code indicates that something is wrong with the website server and the server cannot identify the exact problem. While this is not a client-side issue, the client can try to resolve it with the following steps. 502 – Bad Gateway: This HTTP error code indicates that the server is acting as a gateway or proxy server and cannot receive a valid response from upstream servers or the origin server. This can occur due to the DNS issue.

Troubleshooting Steps: Reload the URL by pressing the F5 key. Start a new browser session by closing all open browser windows. Clear browser cache. Temporarily disable your CDN (Content Delivery Network). Restart your network devices. (modem, router, etc.)

This HTTP error code indicates that the server is acting as a gateway or proxy server and cannot get a valid response from upstream servers or the origin server. This can occur due to the DNS issue. 503 – Service Unavailable: This error code indicates that the server is overloaded or under maintenance and the service should eventually be available.

Troubleshooting Steps: Reload the URL by pressing the F5 key. Reboot your router, modem, and device.

This error code indicates that the server is overloaded or under maintenance and the service should eventually be available. 504 – Gateway Timeout: This error indicates that the server is a gateway or proxy server and cannot get a response from the backend server within the allowed time.

Troubleshooting Steps: Try reloading the URL by pressing the F5 key. Reboot all your network devices like modem, router, etc. Check the proxy server settings in your browser or application and make sure they are correct. Change the DNS server. (If all devices on your network get the same error) If you still get this error message code, contact the website administrator. And if you still get this error, contact your ISP.

This error indicates that the server is a gateway or proxy server and cannot get a response from the backend server within the allowed time.

introduction

The 502 Bad Gateway error is common among website users. There are different possible reasons for this error and different ways to fix it. In this article, we will cover the top possible causes and how users and web developers can solve them.

Use MetricFire’s platform to analyze and troubleshoot your system’s performance. For more detailed information about MetricFire and how to integrate it into your system, book a demo with our team or sign up with MetricFire for the free trial.

What does NGINX 502 Bad Gateway mean?

502 Bad Gateway means the server you are accessing is getting an error from another server. This happens when a server acts as a proxy to get information from another server. Connecting to another server returns an error. NGINX returns error 502 if it cannot connect to PHP-FPM or PHP-FPM is not responding.

There are different names for the 502 error that you may see on different websites. For example:

HTTP Error 502 – Bad Gateway.

HTTP 502.

502 Service temporarily overloaded.

Temporary error (502).

502 Bad Gateway nginx.

502 Bad Gateway.

Error 502.

502 proxy error.

Also, the appearance of the page showing the 502 error can be customized on different websites in the same way as it is for the 404 not found error. There are various causes of error 502. Below we will look at the main as well as possible ways to fix this error.

What is PHP-FPM used for?

PHP-FPM (PHP-FastCGI Process Manager) is a web request processing tool for PHP applications. PHP-FPM together with NGINX can significantly increase the performance of websites while reducing resource consumption.

PHP works as an isolated service when using PHP-FPM. Web requests are processed over a TCP/IP socket, NGINX only processes HTTP requests, and PHP-FPM interprets PHP code. Using separate services is very important to improve efficiency.

Possible reasons for 502 Bad Gateway

Let’s take a look at some of the possible reasons behind the 502 bad gateway.

NGINX is not running

If you see the 502 error, the first thing you need to do is verify that NGINX is running. To do this, run the following command:

systemctl-status nginx

If you see in the response that the status is inactive (dead), you need to start NGINX.

PHP-FPM is not running

The next reason for the 502 error is that PHP-FPM is not running. If you are using Linux, you can check if PHP-FPM is running with the following command:

ps aux | grep php-fpm

If you don’t see any PHP-FPM processes as a result of this command, you need to run PHP-FPM to fix error 502.

PHP-FPM timeout expires

If the server takes too long to respond, a 502 error can be caused by a PHP-FPM timeout. In this case, PHP-FPM will close the connection even before the response is sent and NGINX will return a 502 error. To fix this problem you can increase the PHP-FPM timeout or alternatively examine your application and find out why it is not responding for too long.

Firewall blocks requests

A firewall can block communication between the edge servers and the origin server. Some DDoS protection systems or security plugins of your CMS can also block requests from servers.

A domain name is not allowed

The domain name does not resolve to the specified IP address or to all IP addresses. In this case, you need to change the DNS server and wait for the changes to propagate and become active globally.

Server is not available

The original server is down or there is no connection to this server.

How to solve the 502 error?

Most of the time, the 502 error occurs due to problems on the side of the website. However, there are times when the root cause lies in the user’s device. You can check if only you are having connection problems or other people are also unable to connect to this website. To do this, use any of the tools that check the status of the site and whether it is working or not. For example, use one of the following or similar tools: isitdownrightnow.com, downforeveryoneorjustme.com. To learn more about the cause of Error 502, you can examine the NGINX log file on your computer (/var/log/nginx/error.log).

As a visitor

If you are the only one having connection problems, there are several things you can do to fix the 502 error as a website visitor.

Reload the page in the browser. Often the 502 error is temporary and a simple reboot can help. Clear browser cache and cookies. The browser can store old or corrupted files and data that can cause the 502 error. Try a different browser. There may be a problem in the browser you are using and the error does not appear in another browser. Restart your computer and network devices. Maybe this is the problem and after a reboot the error goes away. Check plugins and extensions in your browser. If you use plugins or extensions and the website works in another browser, they may be blocking the connection. Disable all installed plugins and extensions and check the connection again. Change your DNS server. Changing the DNS server can fix the 502 error. You can choose between Open DNS or Google DNS servers.

As a developer

In most cases, the 502 error occurs to all users because the problem lies within the website. As a web developer, you can:

Check if your server is available. Check the firewall logs for unusual crashes. When using Cloudflare, your visitors will return a 502 Bad Gateway error when a certain limit is reached. Try disabling Cloudflare.

Monitor your system metrics with MetricFire’s Hosted Graphite

To identify bottlenecks and fix errors like error 502, it is helpful to monitor the metrics of your system and the technologies you are using in your application. MetricFire has an open source platform that gives you the tools to monitor and analyze your system’s metrics. MetricFire offers hosted Graphite and hosted Grafana. Grafana is a web-based analytics and data visualization application. You can use it to create various customizable dashboards that can include charts, graphs, and notifications.

Let’s take a look at some of Grafana’s main features:

Dashboard Templates. You can style your dashboard in templates as if you were writing code. Templates allow you to use the same design in different environments. Remarks. You can create logs and comments on your chart manually or automatically. Custom Plugins. Grafana can install external plug-ins that you can use to extend the basic functionality. SQL support. With SQL support, you can easily retrieve data from a variety of data sources. warnings. Grafana can send users notifications about important incidents.

Graphite is a tool for collecting, storing and processing metrics. You can use Graphite as a data source for Grafana. Grafana comes with an advanced Graphite query editor that allows you to write various queries, add functions, change function parameters, accept complex nested queries using query links, and more.

With Hosted Graphite and Grafana, you can track your system performance in real-time. MetricFire offers you hosting services for both tools so you can focus on your system’s performance and monitor its metrics from your browser.

To learn more about how to integrate Graphite and Grafana into your system, book a demo with our team or sign up for the MetricFire free trial today.

Conclusion

In this article, we took a look at what error 502 means, what are the possible reasons for its occurrence and how to fix it. We also found that to troubleshoot your system, it’s important to use monitoring tools like hosted Graphite and Grafana offered by MetricFire.

Book a demo with MetricFire experts or sign up for the free trial today and learn more about our features.

If you’ve ever visited a website that gave you an error page, you know how frustrating it is.

One of the worst things you can do as a brand is not to meet the needs and expectations of your audience. If your website visitors see an error page when looking for help or information, they could become frustrated and lose trust in your brand, permanently damaging your reputation.

The 504 Gateway Timeout Error is a type of error that can affect user experience in this way. To help you not lose brand sentiment and consumer confidence, we have explained exactly what this error means and what are its most common causes and solutions.

What is a 504 gateway timeout error? A 504 gateway timeout error means your web server didn’t get a timely response from another upstream server when it tried to load one of your web pages. Simply put, your web servers aren’t communicating with each other fast enough. Since a 504 gateway timeout error is rather generic, it doesn’t indicate the exact cause of the problem. In this case, your website will show your website visitors an error webpage.

This is how a 504 gateway timeout error can appear in your user’s browser:

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504 error wording

The screenshot above shows how a 504 gateway timeout error is displayed on a server. Below are some other common ways a 504 error can appear, depending on the server, operating system, or browser you’re using.

A 504 error is displayed as HTTP ERROR 504 in Google Chrome. This code appears below a message that reads something like “This website cannot be reached. _____ took too long to reply.”

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In Windows-based programs, a 504 error is displayed as ERROR 504, HTTP_STATUS_GATEWAY_TIMEOUT, or “Request timed out waiting for a gateway message.” This is what it can look like when using Excel:

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During a Windows update, a gateway timeout error generates error code 0x80244023. The message is: WU_E_PT_HTTP_STATUS_GATEWAY_TIMEOUT.

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In other operating systems, web servers, or browsers, a 504 error may also result in the following message – although this is less common: “The proxy server did not receive a timely response from the upstream server.” Here’s a slight variation:

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So now we know how the 504 error is worded, but what exactly does it mean? Let’s decode it below.

What does 504 gateway timeout mean?

When you visit a website, your server sends a request to another server hosting that website. This server – known as the “upstream server” – receives the request and responds with all the resources needed to load the website in your browser.

However, a 504 gateway timeout error means your server didn’t get a response from the upstream server fast enough. Because its request has timed out, your server cannot load the webpage and ultimately fulfill its role as a gateway – hence the name “Gateway Timeout” error.

You may be wondering what exactly is causing the delay in the upstream server’s response – and that’s a good question. Let’s get into that below.

504 gateway timeout causes

504 gateway timeout errors are among the most frustrating HTTP status codes you can get. They indicate what happened to your website, but they don’t tell you why it happened, making it difficult for you to pinpoint the cause and ultimately fix the problem.

Below are a few options.

Server connectivity issues

Most websites are on multiple servers or third-party hosting providers. If your server is down for maintenance or other reasons, your website might show visitors a 504 gateway timeout error page.

DNS changes

If you recently changed servers or moved your website to a different IP address, changes will be made to your website’s DNS server. This could result in your website serving a 504 Gateway Timeout Error page to its visitors. Your website will not be operational until these DNS changes take full effect, which may take a few hours.

Incorrect firewall configurations

Your firewall is your website’s gatekeeper, protecting your website from malicious visitors or distributed denial-of-service (DDoS) attacks. Sometimes, a bad firewall configuration causes your firewall to consider requests from a content delivery network as an attack on your server and reject them, resulting in a 504 Gateway Timeout Error.

Error in your website code

If your website’s code contains an error, your server may not be able to correctly answer requests from a content delivery network.

Network connection error

Since a 504 error is the result of a timeout while processing a request between servers, the problem is likely with them – not the internet connection or the user’s device. However, if just one user reports seeing a 504 error on your site, it could be with their modem, router, or other device. or your internet connection.

Because there can be multiple reasons for a 504 error to appear, it’s ultimately up to you to rule out each one until you find the real cause. Luckily, there are five common and effective solutions to fix most of the causes of 504 gateway timeout errors.

How to fix 504 gateway timeout errors Check for server connection issues. Look for DNS changes. Search your logs. Fix faulty firewall configurations. Comb your site’s code to find errors. Contact your hosting provider.

1. Check for server connection issues.

If your server is down for maintenance or other reasons, your website will likely present visitors with a 504 Gateway Timeout Error page. The only way to fix this problem is to wait for your server to finish maintenance or fix the problem that is causing the error.

2. Look for DNS changes.

If you’ve recently switched hosting providers or moved your website to a different IP address, your website’s DNS server needs to be updated. These DNS changes take a few hours to process, so your website may be showing visitors a 504 gateway timeout error page in the meantime. The only solution is to sit still while these DNS changes take effect.

3. Search your logs.

If the problem isn’t with your server’s connection or DNS information, look at your server logs. These logs contain details about the health and status of your server. Searching them might uncover other issues that could be causing a 504 error.

4. Correct incorrect firewall configurations.

A faulty firewall configuration can be the reason for your 504 gateway timeout error. To rule this out as a cause, you can temporarily disable your firewall.

If your device is running Windows, go to your Control Panel and click Update & Security > Windows Security > Virus & Threat Protection > Manage Settings. On this settings page you can disable your firewall.

If your device runs on Mac OS, simply navigate to System Preferences > Security & Privacy > Firewall to disable it.

After disabling your firewall, check if the 504 error is resolved. If this is the case, you can either reconfigure the settings of your existing antivirus or switch to a new one.

If the error is not resolved, don’t forget to re-enable your firewall before proceeding to the next step.

5. Comb your site’s code to find errors.

Comb your code to find bugs or copy your code to a development machine. It runs a thorough debugging process that simulates the situation where your 504 gateway timeout error occurred and allows you to see the exact moment when something went wrong.

6. Contact your hosting provider.

Contacting your hosting provider should be the last resort. But if you’ve tried the steps above and still see the 504 gateway timeout error, they might be able to solve the problem or provide valuable insights.

How 504 gateway timeout errors affect SEO

Fixing a 504 gateway timeout error can take time—but it’s worth it when you consider how it can affect your site’s technical SEO.

Like an internal HTTP server error 500, 503 error, or any other 5xx error, a 504 gateway timeout error will prevent your website from loading. This not only harms the user experience but also your SEO performance.

If a web crawler tries to crawl one of your pages and gets a 504 error, it can’t crawl the page. If this page has already been indexed, it may move down in search engine results. Or it could be deindexed if the error persists.

Fixing the 504 gateway timeout error

There is no foolproof way to prevent 504 gateway timeout errors on your website, but there are steps you can take to fix them. By fixing this error as soon as possible, you ensure that visitors continue to have a seamless experience on your website and mitigate any negative impact on your SEO.

Editor’s Note: This post was originally published in January 2019 and has been updated for completeness.

Nginx is the most popular web server and reverse proxy server ever for high traffic websites.

It stays strong even under heavy traffic and helps achieve high uptime.

But like any other server, Nginx is prone to configuration and connection issues that lead to Nginx upstream errors.

The result is website downtime and negative impact on SEO.

“502 Bad Gateway” is one such common Nginx upstream error.

At Bobcares, our 24/7 monitoring service engineers monitor the servers and quickly fix such Nginx upstream errors.

What are Nginx upstream errors?

In reverse proxy, it accepts a request from the client, forwards it to the upstream server (server that can complete the request), and returns the server’s response to the client.

Nginx upstream errors occur while the proxy server receives an invalid response or no response from the origin server.

Visitors see different variations of these errors like:

502 bad gateway 502 bad gateway nginx 502 proxy error 504 gateway timeout HTTP 504 gateway timeout

These messages are cryptic.

Therefore, many webmasters look at their error log:

11/01/2018 18:15:02 [Error] 1713#0: *1 upstream timed out (110: connection timed out) connecting to upstream, client: xx.xx.xxx.xxx, server: , request: ” GET / HTTP/1.1″, upstream: “http://xx.xx.xx.xx:8082/”, host: “xx.xx.xx.xx”

You can see something is messed up but not sure where to start.

This is where you need an expert to figure it out quickly and fix it permanently.

Today, let’s discuss the different reasons behind nginx upstream errors and how our dedicated server admins fix them.

Nginx Upstream Errors – Top 6 Reasons and Solutions

In our experience of dealing with nginx upstream errors, we will see the main causes that we encountered.

1. High load on the origin server

High load peaks lead to services not responding.

Therefore, Nginx cannot communicate with the origin server and lead to this error.

The most common reasons for load peaks are:

Compromised server sending malware or spam.

Heavy website traffic (can be marketing, advertising, etc.).

Brute force attacks to exploit web applications.

Application bugs that cause resource hogging and memory leaks.

How do we fix?

Our hosting engineers first identify the resource that is being abused. Then we find out which service is abusing this resource.

At this point we identify the user who owns the script or software for abusing the service.

2. Service Downtime on Origin Server

Nginx depends on various services like Apache, PHP-FPM, database services, etc. to run applications.

If any of these services crash, Nginx will not receive any data and will result in errors.

How do we fix?

The reasons for service failures can be traffic spikes, resource failures, DDOS attacks, disk failures, etc.

We will identify and fix this reason.

If a backend service goes down or isn’t responding, we kill all dead processes and restart the service.

3. Firewall blocks a request

The firewall is the cornerstone of server security. If not configured properly, it can block legitimate requests or services.

By default, the firewall blocks unusual ports on the server.

If you’ve enabled a new service (e.g. Ruby) on the server and it’s running on a custom port, chances are that port is blocked in the firewall.

Hence, Nginx cannot communicate with this service and lead to this error.

How do we fix?

To fix that, let’s look at what port each service is running on using the netstat command.

If we find that a service is running on custom ports, we’ll edit the firewall configuration to allow those custom ports.

4. Network Issues

DNS issues, routing issues, and ISP issues can cause Nginx upstream errors.

If recent DNS changes have been made, e.g. B. changing name servers, hosting servers, etc. will take time to spread globally. The domain may not be forwarded during this period.

Also, ISPs can sometimes block access to a specific website.

All of these can lead to such errors.

How do we fix?

We check the DNS connectivity of the domain with the command:

Dig up Domain.com

We also access the domain from third-party proxy servers to determine if this error is specific to the customer.

If DNS conflicts are found, we will fix them quickly. If the problem is with the ISP, it needs to be fixed there.

5. Server Software Timeouts

Nginx upstream errors can also occur when a web server takes more time to complete the request.

At this point, the caching server reaches its timeout values ​​(the connection between the proxy and the upstream server times out).

Slow queries can cause such problems.

How do we fix?

We will tweak the following Nginx timeout values ​​in the Nginx configuration file.

proxy_connect_timeout 1200s; proxy_send_timeout 1200s; proxy_read_timeout 1200s; fastcgi_send_timeout 1200s; fastcgi_read_timeout 1200s;

Once the timeout values ​​are added, you need to reload nginx to save these parameters.

6. Errors in application code

If all other checks have failed, there may be a bug in your web application code.

Sometimes your application code may not be compatible with the server version which causes this error to appear.

How do we fix?

We will diagnose the problem by analyzing the application and web server logs.

We also review your application’s software requirements and reconfigure the services to the required version.

Conclusion

Nginx upstream errors occur when Nginx runs as a reverse proxy and cannot connect to the upstream servers. Today we have seen the top 6 reasons behind this error and how to fix it.

Have you ever been frustrated with proxy error codes you received while using proxies but have no idea why? Proxy error codes are similar to HTTP status codes. By learning what these errors mean, you can run your scraping activities smoothly and also automate your IP settings.

It is very likely that you will get such errors if you don’t properly manage your proxies during crawling or scraping activities. Problems can either come from your side (client side) or from the server side. In this article, you’ll learn about the most common types of proxy errors, why you get them, and how to fix them.

What is a proxy error?

A proxy error is an HTTP error status that you receive in response when a request sent to the web server through a proxy fails. In any case, to continue using the proxy, you need to find a solution. The response returned during a request failure can seem a bit confusing. If you are familiar with HTTP status codes, understanding proxy errors is not a problem.

status code classes

HTTP status codes are displayed as three digits. They are divided into five classes, so the first digit of each error code represents the class.

They are;

1. 1xx – Informational

2. 2xx – success

3. 3xx – Redirect

4. 4xx – Client Error

5. 5xx – Server Error

Common proxy error codes and their

solutions

1xx Informational error code

These are tentative answers, rarely used. These requests are considered used when the server processes the requests;

100 – Next

The code indicates that part of the request has been received and the client can continue sending the remaining request. Typically, the client first sends a request header with the directive “Expect: 100-continue” and gets the 100 status code from the server to send the request body. The “expectation” in the initial request is to avoid sending further requests if the server rejects the initial request header.

101 – Mediation Protocols

A web server sends a 101 status code when the browser requests to change the communication protocol during a transaction. If the client browser’s request asks the server to switch communication protocols and accepts, it sends the HTTP status code “100 – Switching Protocols” as confirmation.

102 – Processing (WebDAV)

The web server may need some time to process complex requests. When a client’s browser sends a WebDAV request with multiple sub-requests with complex requirements, the server takes some time to process and eventually sends this “102 – Processing” code. This code aims to avoid client-side timeout errors by informing the client that the server received and processed the request.

103 – Early Notes

The 103 – Early Hints code is received by the web server when sending the HTTP status to the browser before the HTTP requests are processed. The name indicates that this is an early indication to the client’s browser that the server has not yet started processing the requests.

2xx successful status code

Receiving codes between 200 and 299 means your proxy received your HTTP request, sent it to your intended website, and received a response. 200 is the most frequently received code, which informs that the server has successfully fulfilled the request. Look for any 2xx code other than 200 OK as it may indicate an error.

Here are the most common 2xx status codes;

201 – Created

This status code indicates that the server has completed the received request from the client and created a new resource based on the received request. The initial request acts as a trigger to generate a new response in the server. For example, when a server generates a new response based on a user’s credentials.

202 – Accepted

202 – Accepted is returned when the server receives the request from the client but has yet to process it. This is the only indication for accepting the request, but the result of processing the request will be known later when the “actual processing” takes place.

203 – Non-binding information

The code “203 – Non-Authoritative Information” was received when the server successfully processed the request, but returned the information from another resource to the requested client.

204 – No content

The server cannot find any content for the received request; It sends a 204 – No Content response code, which indicates to the client that no content will be returned.

205 – Reset content

Similar to the 204 code above. A request was successfully processed by the server, but no content is returned. The only difference is that the 205 code informs the client to reset the document view.

206 – partial content

A server returns this error code when it sends any part of the requested resource that is affected by the scope mentioned in the request header.

For example, the client requests a set of files to download and uses multiple streams to download the full content.

3xx – redirect error

3xx codes indicate that additional action is required from the client side to fulfill the request.

These status codes are not a problem if you use a browser (e.g. Google Chrome or Safari), but if you use your own script. Scripts you write and if there is no need to redirect the requests to other URLs will come in handy.

Because these actions can create infinite loops, web browsers typically follow no more than five consecutive redirects of the same request.

Some of the most common 3xx error codes are as follows:

300 – multiple choice

It occurs when a requested URL points to more than one resource.

The user-agent (crawler or web browser) cannot decide which page to fetch and receives an HTTP code “300 – Multiple Choices”.

Fix error code 300 by checking the HTTP headers and making sure the URL points to a single resource – so the user agent can successfully access the page.

301 – Resource moved permanently

This error is received when a permanent redirect to an original URL is set to redirect the user agent to a different URL.

If a web server sends the status code “301 – Moved Permanently” because a user cannot see the original URL, search engines would only index the redirected URL. Most search engine crawlers and user agents can track up to 5 redirects for a single URL. More than five redirects can lead to an infinite loop, and browsers like Chrome display a message like “Too Many Redirects”.

A 301 code is the most popular of all 3xx server response codes.

302 – Resource moved temporarily

A 302 – Moved Temporarily code is received when a temporary redirect is set to the original URL. This means that the user agent will be redirected to another URL after the request.

303 – See another resource

A “303 – See Another Resource” is received when the requested resource is at a different URL, and it should be requested using a “GET” method instead of code. Note that the originally requested page will only be indexed by the search engines if the code “200 – Success” is received.

304 – Resource not changed

A server would respond with the code “304 – Resource not changed” if the requested resource has not changed since the last request.

In this case, the server would assume that the data doesn’t need to be resent since the client already has a copy of the requested resource that hasn’t been modified.

Note that the “last time modified” is mentioned in the request header “If-Modified-Since” or “If-Match”.

Also, if your webpage has not changed since the last time search engine crawlers accessed your site, it is recommended to return the 304 code to speed up indexing and reduce crawler load.

305 – Use proxy

The 305 – Use Proxy code is displayed when the requested resource can only be accessed through a proxy server. The address of the proxy server is also received in the response and displayed in the browser window.

Some browsers such as Internet Explorer do not properly display this response due to security concerns when viewing the proxy server.

306 – Switch Proxy

The code “306 – switch proxy” indicates that the server should use the specified proxy for the following request(s).

307 – Temporary Redirect

A 307 – Temporary Redirect code is received when a requested resource is temporarily moved to a different address specified in the location header of the request. This is only a temporary redirect, but the next request should access the original URL. By the way, only the HTTP/1.1 protocol uses this status code.

308 – Permanent redirect

A “308 – Permanent Redirection” code is an experimental code to indicate a permanent redirect (similar to 307 set as a temporary redirect). Codes 307 and 308 are similar to codes 302 and 301, with the slight difference that the HTTP method is not changed.

4xx client error codes

The main types of HTTP proxy errors are 4xx and 5xx error codes. Receiving an error from the 4xx series indicates that the problem is on the client side. This can be your request, your browser or the automation bot.

400 – Invalid request

It’s a generic response indicating that there is a problem with your sent request. Sometimes your proxy server or the target website may not be able to parse your request. Problems can be malformed syntax, invalid formatting, or misleading request routing.

401 not authorized

The 401 – Unauthorized error code indicates that you are trying to access an unauthorized website that requires you to authenticate yourself.

The error is returned from the proxy server when the web server requires authentication and authorization. You can access the resource by providing credentials.

402 – Payment required

This response code is primarily set for future use. Even though this status code is relatively rare and no uniform convention exists, the goal in creating this code was for digital payment systems.

403 Forbidden

403 indicates that your request is valid and understood by the proxy or web server, but refuses to respond. This happens when you don’t have permission to view the resource.

404 Not found

This code is returned by the proxy server when the requested online resource is not available, even if the request is valid. Although 404 is primarily known as a “client error”, it results from dead links. This could mean that the URL has been removed, is incorrect, or has been modified without redirecting.

405 – Method not allowed

405 is received when a request method is known to the server but has been disabled and cannot be used. For example, an API request can forbid

“DELETE” a resource. Both mandatory methods, GET and HEAD, must never be disabled and should not return this error code.

406 – Not acceptable

A response is sent if, after performing server-driven content negotiation, the web server does not find any content matching the criteria specified by the user-agent.

407 – Proxy authentication required

A proxy displays a 407 code when authentication is required or when a tunnel fails to connect. This can happen if your scraper is not correctly authenticated with the proxy provider or if the credentials are inaccurate. Another reason may be that you are not whitelisting your IPs in the proxy settings.

To fix this error, you need to update your proxy settings by adding whitelisted IPs and entering the correct credentials. Also, make sure that all required information is also included in the request.

408 Request timed out

This error code is received when a client has not generated a request while the server is configured to wait or hold. The client can repeat the request at any time without changing it.

If the 408 error persists, check the load generated on your web server when you spot the errors. Another possibility could be connection problems.

409 – Conflict

The 409 conflict usually has nothing to do with the authority or security of the default web server, but with a specific application, conflicts that are not defined in the HTTP protocol itself.

The web server responds with this error when it considers the client’s requests to be legitimate, but a request could not be completed due to a conflict with the current state of the resources. The response body usually contains enough information for users to identify the cause of the conflict and troubleshoot the problem.

410 – way

The web server responds with this error code when the requested resource is no longer available through the server, will not be available again, and has no known forwarding address. This error is similar to the 404 error, but 410 is a permanent error.

411 – Length required

This error code means that the server refuses to accept the request without a defined content length. The client should repeat the request by adding a valid Content-Length header field containing the length of the message body in the request’s message.

412 – Precondition failed

The web server responded with this error code when preconditions are specified in one or more of the request header fields that evaluated as false when tested on the server.

This status code allows the client to place preconditions on current resource meta information (header field data) and prevents the requested method from being applied to a resource other than the originally intended one.

413 – Request unit too large

The server refuses to process a request because the request entity is larger than what the server can handle. The server could close the connection to prevent the client from sending more of the same request.

“What is ‘too large’ depends in part on the surgery being attempted. For example, a request to upload large files (via the HTTP PUT method) may encounter upload file size limits set by the web server.”

414 – Request URL too long

The web server responds with this error when it refuses to serve the request because the request URL is longer than the server can handle. This rare condition is more likely to occur when a client has incorrectly converted “POST” requests to “GET” requests, with long query information, once the client has entered a URL redirection “black hole” (meaning that a redirected URL prefix showing a custom suffix) or

This error code can also be received when the server is being attacked by a client trying to exploit vulnerabilities that exist on some servers, also using fixed-length buffers for reading and manipulating request URLs. Typically, web servers set fairly generous length limits on real URLs. If a long URL is valid and you still get a 414 error code, it means the web server may need to be reconfigured to allow such URLs through.

415 – Unsupported media type

The web server refuses to complete the request because the request’s entity is in formats not supported by the requested resource for the requested method.

416 – Requested range not satisfiable

The 416 status code is received when a server’s response usually returns 416 when a request contains a “Range” request header field. No range-specific values ​​in this field overlap the current extents of selected resources, and the request had no If-Range request header field.

For example, if the resource is a 1000 bytes file and the requested range is 500-1500, this may not be sufficient as an acceptable range.

417 – Expectation failed

The web server typically responds with this status code when the expectation received in an “Expect” request header field cannot be met by the server, or when the server is a proxy and has strong evidence that the next-hop server has the could not fulfill request.

429 – Too many requests

This error is likely to occur when too many requests are sent within a limited time frame while using the same IP address. Websites typically implement such restrictions to protect themselves from attackers and avoid overloading.

Using rotating proxies can fix this error code by setting delays between requests per IP and per a specific time frame.

5xx – Server Error

Series of 5xx is returned when the server successfully receives the request but cannot process the request or encounters a problem processing it.

To fix all those 5xx errors, rotate IPs and change proxy network and IP type. Using a private proxy network is better in such cases to rotate IPs and ensure reliability.

You may get error codes like –

500 – Internal server

The 500 – Internal Server error code is received when the server encounters an unexpected condition that prevents it from responding to the request.

501 – Not implemented

The 501 – Not Implemented error is received when the server cannot provide the requested resource due to an unsupported or unrecognized method(s) in the request.

502 Bad Gateway

This error often occurs during data collection when the server is acting as a gateway or proxy and receives an invalid response from another server.

When super proxies refuse the Internet connection or sent requests, the unavailability of IPs for selected settings is detected, as bots display 502 code.

503 – Services not available

The 503 – Service Unavailable code is received when a server receives the request at the same time as other requests are overloading it, or is in scheduled downtime/maintenance. In this case, check the status of the requested server if possible.

504 – Gateway Timeout

“504 – Gateway Timeout” is received when a server (a) is acting as an external gateway or proxy and does not get the response in time from the next server (b) that is further up the request chain trying to fulfill the request.

505 – HTTP version is not supported

A “505 – HTTP Version Not Supported” code is received when a server does not support the HTTP protocol version and is used in the request message.

507 – Insufficient disk space

“507 – Insufficient Storage” means that the server has run out of disk space and is no longer fulfilling the request.

510 – Extensions are missing

The server cannot process the request because an unsupported extension is requested, then the code “510 – Not Extended” is received.

Solving common proxy error codes

The easiest way to solve these proxy error codes is to use a proxy manager. A proxy manager is often free, open-source software that automates proxy management to avoid such errors. To prevent the 407 error code, you need to choose a proxy port. Then all related credentials and zone information will be updated automatically.

You can apply specific actions in your proxy manager when a rule you apply is triggered. To avoid errors like 403 it is important to rotate your IPs; Hence, home proxies are the best option. NetNut can do its part by integrating with your proxy tools to avoid these errors. Learn how to integrate NetNut to configure your proxy settings.

Also check out our GitHub repositories for a better understanding of advanced usage with our proxies, code documentation, and walkthroughs.

In summary, the basic steps you can follow to fix these proxy errors are:

1. Switch to residential proxies

Although home proxies are a bit more expensive, unlike data center proxies, they offer a large pool of proxies. Therefore, you can rotate your IPs and avoid getting blocked.

NetNut is a better example of a private proxy service provider that uses a dynamic P2P + ISP proxy network and offers both rotating and static private IPs.

2. Reduce the number of requests

Sending too many requests at once makes any website suspicious. Set a slight delay between requests to avoid errors.

3. Improve IP rotation

As explained above, using a proxy management tool helps accomplish this task. Control your IP sessions to minimize requests from the same IP address.

4. Have a good working scraper

Following the above factors but using a poorly performing scraper can still lead to errors. Therefore, make sure you have an advanced scraper to bypass obstacles implemented by websites.

Remember!

The first steps to overcoming these proxy errors is to understand the error code and why you are getting such a code. By understanding such causes while implementing these techniques, you can run your data collection smoothly and minimize errors.

Can’t find a solution to your error code? Ping us via email and our support experts can help!

The 504 Gateway Timeout error is an HTTP status code that means that a server did not receive a timely response from another server it accessed when trying to load the webpage or fulfill another request from the browser.

In other words, 504 errors usually indicate that another computer, which the website you’re receiving the message from doesn’t control but relies on, isn’t communicating with it fast enough.

Wire of Life / Ashley Nicole DeLeon

Are you the web manager? See the “Fixing 504 Errors on Your Own Site” section further down the page for a few things to consider on your site.

A 504 gateway timeout error can appear on any internet browser, operating system, and device. This means that it is possible to get the error on your Android or iPhone phone or tablet, in Safari on a Mac, in Chrome on Windows 10 (or 8 or 7,…) etc.

How you might see the 504 error

Individual websites can customize how they display “Gateway Timeout” errors, but here are the most common ways you’ll see one spelled out:

504 Gateway timeout

HTTP 504

504 ERROR

Gateway timeout (504)

HTTP Error 504 – Gateway Timed Out

Gateway timeout error

A 504 gateway timeout error is displayed in the internet browser window just like regular websites. It can be the familiar website headers and footers and a nice English message on the page, or it could be displayed on an all-white page with a big 504 at the top. It’s always the same message regardless of how the website displays it.

Causes of 504 gateway timeout errors

Most of the time, a 504 gateway timeout error means that any other server that’s taking so long to “time out” is likely down or not working properly.

Since this error is usually a network error between servers on the internet or an issue with an actual server, the problem is probably not with your computer, device, or internet connection.

That said, there are a few things you can try, just in case:

How to fix 504 gateway timeout error

Try the webpage again by selecting the refresh/reload button, pressing F5, or trying the URL from the address bar again. Even though the 504 gateway timeout error reports an error beyond your control, it might only be temporary. Reboot all your network devices. Temporary problems with your modem, router, switches, or other network hardware can cause the 504 gateway timeout issue you’re seeing. Rebooting these devices might help. While the order in which you turn off these devices isn’t important, the order in which you turn them back on is important. Generally, you want to turn on devices from the outside in. If you’re not sure what that means, see the link at the beginning of this step for a full tutorial. Check the proxy server settings in your browser or application and make sure they are correct. Incorrect proxy settings can cause 504 errors. Windows 10 proxy settings. Most computers have no proxy settings at all. So if yours are empty, just skip this step. Change your DNS servers especially if all the devices on your network are getting the same error. It’s possible that the 504 gateway timeout error you’re seeing is caused by a problem with the DNS servers you’re using. Unless you’ve changed them before, the DNS servers you have configured now are likely the ones automatically assigned by your ISP. Others are also available. See our list of free and public DNS servers for options. If nothing has worked up to this point, contacting the website is probably the next best thing. There is a good chance that the website admins are already working to fix the root cause of the 504 gateway timeout error assuming they are aware of it, but there is nothing wrong with reaching out to them. Most major websites have social networking accounts that they use to support their services, and some even have phone numbers and email addresses. If it seems like the site is throwing a 504 error for everyone, it’s often helpful to scour Twitter for real-time information about the site’s downtime. The best way to do this is to search #websitedown on Twitter. For example, if Facebook isn’t available, search for #facebookdown. Contact your internet service provider. It’s very likely at this point that the 504 Gateway Timeout you’re seeing after trying all of the above troubleshooting is a problem caused by a network issue that your ISP is to blame for. 7 Tips to Make Working with Tech Support Just a Little Easier Come back to these later. You have exhausted all your options at this point and the 504 gateway timeout error is in the hands of either the website or your ISP to correct it. Check the site regularly. No doubt it will work again soon.

Fix 504 errors on your own website

Often this isn’t your fault at all, but it’s not the user’s either. First, verify that your server can properly resolve all domains that your applications need access to.

Very heavy traffic can cause your server to return a 504 error, although a 503 would probably be slightly more accurate.

In WordPress specifically, 504: Gateway Timeout messages are sometimes due to corrupted databases. Install WP-DBManager and then try the “Repair DB” function followed by “Optimize DB” and see if that helps.

Also, make sure your HTACCESS file is correct, especially if you just reinstalled WordPress.

Finally, consider contacting your hosting company. It’s possible that the 504 error your website is returning is due to a problem on their end that they need to fix.

More ways you might see a 504 error

A gateway timeout error, when received in Windows Update, generates a 0x80244023 error code or the message WU_E_PT_HTTP_STATUS_GATEWAY_TIMEOUT.

Windows-based programs that inherently access the Internet may see a 504 error in a small dialog box or window with an HTTP_STATUS_GATEWAY_TIMEOUT error and/or the request timed out while waiting for a gateway message.

A less common 504 error is Gateway Timeout: The proxy server didn’t get a timely response from the upstream server, but troubleshooting (above) remains the same.

Errors like 504 gateway timeout

A number of error messages are similar to the 504 gateway timeout error as they all occur on the server side. These include the 500 Internal Server Error, the 502 Bad Gateway Error, and the 503 Service Unavailable Error.

There are also HTTP status codes that are client-side rather than server-side, like the commonly seen 404 Not Found error. There are several others as well, all of which you can see on our HTTP Status Code Errors page.

You look at the Apigee Edge documentation.

Check out the Apigee X documentation.

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videos

Watch the videos below to learn more about fixing 500 internal server errors.

Video Description Introduction Provides an introduction to 500 internal server errors and possible causes. Also shows a 500 Internal Server real-time error along with steps to troubleshoot and fix the error. Handling Service Callout and Extract Variables Errors Illustrates two 500 internal server errors caused by Service Callout and Extract Variables policies and shows how to troubleshoot these errors. Handling JavaScript Policy Errors Displays an internal server error of type 500 caused by a JavaScript policy and the steps to troubleshoot and resolve this error. Handling Back-End Server Errors The example shows 500 internal server errors caused by an error on the back-end server and steps to resolve the errors.

symptom

The client application receives an HTTP status code of 500 with the message “Internal Server Error” in response to API calls. The 500 Internal Server error can be caused by an error during the execution of any policy in Edge or by an error on the target/backend server.

The HTTP status code 500 is a generic error response. This means that the server encountered an unexpected condition that prevented it from fulfilling the request. This error is typically returned by the server when no other error code is appropriate.

error messages

You may get the following error message:

HTTP/1.1 500 Internal server error

In some cases, you may see a different error message that provides more detail. Here is an example error message:

{ “fault”:{ “detail”:{ “errorcode”:”steps.servicecallout.ExecutionFailed” }, “faultstring”:”Execution of ServiceCallout callWCSAuthServiceCallout failed. Reason: ResponseCode 400 is treated as an error” } }

Possible causes

The 500 Internal Server Error can be triggered due to various causes. In Edge, the causes can be divided into two main categories depending on where the error occurred:

Cause Details Detailed troubleshooting steps are provided for execution errors in an edge policy A policy inside the API proxy can fail for some reason. Edge Private and Public Cloud Users Backend Server Error The backend server can fail for some reason. Edge Private and Public Cloud users

Execution error in an edge policy

A policy inside the API proxy can fail for any reason. This section explains how to troubleshoot when the internal server error 500 occurs during policy execution.

diagnosis

Note: The 500 Internal Server error can appear for many different reasons. For example, a 500 error can occur when a policy is executed, or it can originate on the backend target server. That’s why we’ve provided some general diagnostic steps below to help you identify and fix this type of problem. We also provide several examples that provide specific steps to resolve these errors, depending on the cause of the issue.

Diagnostic steps for private and public cloud users

If you have the trace UI session for the error then:

Verify that the error was caused by a policy execution. For more information, see Determining the cause of the problem. If the error occurred during policy execution, continue. If the error was caused by the backend server, go to Backend server error. Select the API request that fails with 500 Internal Server Error in the trace. Examine the request and select the specific failed policy or flow named “Error” that immediately follows the failed policy in the trace. You can get more details about the error by checking either the Error field in the Properties section or the error content. Using the details you have gathered about the error, try to determine the cause.

Diagnostic steps for Private Cloud users only

If you don’t have the trace UI session then:

Verify that the error occurred while executing a policy. For more information, see Determining the cause of the problem. If the error was caused by policy execution, continue. If the error occurred during policy execution, continue. If the error was caused by the backend server, go to Backend server error. Use the Nginx access logs as described in Determining the source of the problem to determine the faulty policy in the API proxy and also the unique request message ID. Check the message processor logs ( /opt/apigee/var/log/edge-message-processor /logs/system.log ) and look for the unique request message ID in them. Once you find the unique request message ID, see if you can get more information about the cause of the error.

resolution

Once you determine the cause of the policy issue, try to fix the issue by repairing the policy and redeploying the proxy.

The following examples show how to find the cause and solution for different types of problems.

If you need further assistance troubleshooting 500 Internal Server Error or suspect it is an issue in Edge, contact Apigee Support.

Example 1: The service callout policy failed due to an error in the backend server

If the call to the backend server within the service callout policy fails with an error like 4XX or 5XX, it is treated as a 500 Internal Server Error.

Here is an example where the backend service fails with a 404 error within the service callout policy. The following error message is sent to the end user: { “fault”: { “detail”: { “errorcode”:”steps.servicecallout.ExecutionFailed” },”faultstring”:”Execution of ServiceCallout service_callout_v3_store_by_lat_lon failed. Reason: ResponseCode 404 is reported as Error handled” } } } The following Trace UI session shows the 500 status code caused by an error in the service callout policy: In this example, the “error” property lists the reason why the service callout failed policy as “ResponseCode 404 is treated as an error”. This error can occur when the resource accessed through the backend server URL in the service callout policy is not available. Check the availability of the resource on the backend server. It may be temporarily/permanently unavailable or moved to another location.

Example 1 resolution

Check the availability of the resource on the backend server. It may be temporarily/permanently unavailable or moved to another location. Correct the backend server URL in the service callout policy to point to a valid and existing resource. If the resource is temporarily unavailable, try making the API request as soon as the resource becomes available.

Example 2: Extract variables policy failed

Now let’s look at another example where 500 Internal Server Error is caused due to error in Extract Variables Policy and see how to troubleshoot and fix the problem.

The following trace in the UI session shows status code 500 due to an error in the variable extracting policy: Select the failed extracting variable policy, scroll down and look at the Error Contents section to see to get more details:

The error content indicates that the variable “serviceCallout.oamCookieValidationResponse” is not available in the extract variable policy. As the name of the variable suggests, it should contain the response from the previous service callout policy. Select the service callout policy in the trace and you may find that the serviceCallout.oamCookieValidationResponse variable has not been set. This indicates that the call to the backend service failed, resulting in an empty response. Even though the service callout policy failed, the policies after the service callout policy continue to run because the “ContinueOnError” flag in the service callout policy is set to true as shown below:

Callout.OamCookieValidation false serviceCallout.oamCookieValidationResponse http://{Url} Note the unique message ID “X-Apigee.Message-ID” for this specific API request from the trace as follows: Select the “Analytics Data Recorded” stage from the request. Scroll down and note the value of X-Apigee.Message-ID. Note: The following steps can only be performed by the Edge Private Cloud users. View the message processor log ( /opt/apigee/var/log/edge-message-processor/system.log ) and look for the unique message ID you noted in step 6. The following error message was observed for the specific API request: 2017-05-05 07:48:18,653 org:myorg env:prod api:myapi rev:834 messageid:rrt-04984fed9e5ad3551-c-wo-32168-77563 NIOThread@5 ERROR HTTP.CLIENT – HTTPClient$Context.onTimeout() : ClientChannel[C:]@149081 useCount=1 bytesRead=0 bytesWritten=0 age=3002ms lastIO=3002ms .onConnectTimeout connectAddress=mybackend.domain.com/XX.XX.XX .XX:443 resolveAddress=mybackend.domain.com/XX.XX.XX.XX The error above indicates that the service callout policy failed due to a timeout error while connecting to the backend server. To determine the cause of the connection timeout error, telnet to the backend server from the message processors. The telnet command gave the connection timed out error shown below: telnet mybackend.domain.com 443 Trying XX.XX.XX.XX… telnet: connect to address XX.XX.XX.XX: Connection timed out This error Occurs under the following circumstances: When the backend server is not configured to allow traffic from the Edge message processors.

If the backend server is not listening on the specific port. In the example shown above, although the extract variables policy failed, the root cause was that Edge was unable to connect to the backend server in the service callout policy. And the cause of this error was that the backend end server was not configured to allow traffic from the edge message processors. Your own extract variable policy behaves differently and may fail for a different reason. Depending on the cause of the error, you can fix the problem according to your extract variable policy by checking the message in the error property.

Example 2 resolution

Resolve the root cause of any errors or failures in the Extract Variables policy accordingly. In the example shown above, the solution was to correct the network configuration to allow traffic from edge message processors to your backend server. To do this, the IP addresses of the message processors were allowed-listed on the respective back-end server. For example, on Linux, you could use iptables to allow traffic from the IP addresses of the message processor on the backend server.

Example 3: Error in JavaCallout policy

Now let’s look at another example where 500 Internal Server Error is caused due to a bug in the Java callout policy and see how to troubleshoot and fix the problem.

The following UI trace shows the status code 500 due to an error in the Java callout policy: Select the flow named “Error” followed by the failed Java callout policy to get the error details, as shown in the image below : In this example, “error” property in the Properties section shows that the error is due to an expired password used when connecting to the Oracle database within the JavaCallout policy. Your own Java callout behaves differently and fills in a different message in the error property Check the JavaCallout policy code and confirm the correct configuration to use.

Example 3 resolution

Correct the Java callout code or Java configuration accordingly to avoid the runtime exception. In the Java callout error example above, one would need to use the correct password to connect to the Oracle database to resolve the issue.

Backend server error

A 500 Internal Server Error can also come from the backend server. This section explains how to troubleshoot when the error comes from the backend server.

diagnosis

Diagnostic steps for all users

The cause of other backend errors can be very different. You must diagnose each situation independently.

Verify that the error was caused by the backend server. For more information, see Determining the cause of the problem. If the error was caused by the backend server, continue. If the error occurred during policy execution, go to Edge Policy Execution Errors. Perform the following steps depending on whether you have access to a trace session for the failing API or whether the backend is a Node.js server:

If you don’t have a trace session for the failed API call:

If the UI trace for the failed request is not available, check the backend server logs for details about the error. If possible, enable debug mode on the backend server to get more details about the error and the cause.

If you have a trace session for the failed API call:

If you have a trace session, the following steps will help you diagnose the problem.

In the trace tool, select the API request that failed with 500 Internal Server Error. Select the Received response from target server phase from the failed API request as shown in the following image: Check the Response Content section for details about the error. In this example, the response content, which is a SOAP envelope, displays the error string as an “Unauthorized” message. The most likely cause of this problem is that the user is not submitting the correct credentials (username/password, access token, etc.) to the backend server. This issue can be resolved by passing the correct credentials to the backend server.

If the backend is a Node.js server:

If the backend is a Node.js backend server, check the Node.js logs for the specific API proxy in the Edge UI (both public and private cloud users can check the Node.js logs) . If you are an Edge Private Cloud user, you can also check your message processor logs ( /opt/apigee/var/log/edge-message-processor/logs/system.log ) for more details about the error.

NodeJS Protocols option in Edge UI – API Proxy Overview tab

resolution

Once you identify the cause of the error, troubleshoot the issue on your back-end server. If it’s a Node.js backend server: Check if your custom code is throwing the error and fix it if possible. If your custom code is not throwing the error or you need help, contact Apigee Support.

If you need further assistance troubleshooting 500 Internal Server Error or suspect it is an issue in Edge, contact Apigee Support.

Determining the cause of the problem

Use one of the following methods to determine if the internal server error 500 was thrown while executing a policy in the API proxy or from the backend server.

Using Trace in the UI

Note: The steps in this section can be performed by both public and private cloud users.

If the issue persists, enable UI tracing for the affected API. After capturing the trace, select the API request that shows a 500 response code. Navigate through each stage of the failed API request and see which stage is returning the 500 Internal Server Error: If the error is triggered during the execution of a policy, then continue to Execution Errors in an Edge Policy. If the backend server responded with 500 Internal Server, go to Backend server error.

Use API monitoring

Note: The steps in this section can only be performed by public cloud users.

With API monitoring, you can quickly isolate problem areas to diagnose error, performance, and latency issues and their source, e.g. B. Developer apps, API proxies, backend targets or the API platform.

Walk through an example scenario that shows how to use API Monitoring to troubleshoot 5xx issues with your APIs. For example, you might want to set up an alert to be notified when the number of 500 status codes or steps.servicecallout.ExecutionFailed errors exceeds a certain threshold.

Using Nginx access logs

Note: The steps in this section apply only to Edge Private Cloud users.

You can also refer to Nginx access logs to determine if the 500 status code was thrown during policy execution in the API proxy or by the backend server. This is especially useful if the problem has happened in the past or if the problem is intermittent and you can’t capture the trace in the UI. Use the following steps to get this information from Nginx access logs:

Error May 16, 2022 Nabilla R. 9min reading time

How to Fix 502 Bad Gateway Error

The reasons behind the 502 error can be numerous, from minor browser-related issues to problems with CDNs. This article describes some troubleshooting steps to follow when encountering a 502 Bad Gateway error, both on server and client side. We will also look at the different factors that can cause this error and the impact they can have on your website’s SEO.

Download e-book: Build your first website in 9 easy steps

Error Code 502 Bad Gateway Error Error Type Server Side Error Error Variations Temporary Error (502)

HTTP Error 502 Bad Gateway

502 proxy error

Bad 502 gateway

502 Service temporarily overloaded

A blank white screen error causes an unresolved domain name

Server overloaded

browser problems

Home network device error

Firewall blocked

How to Fix 502 Bad Gateway Error – Video Tutorial

Looking for a simple visual guide? Watch the video below.

Subscribe for more instructional videos! Hostinger Academy

What is a 502 Bad Gateway Error? The 502 Bad Gateway error indicates that the server you are connecting to received an invalid response. When visiting a URL, your browser sends an HTTP request to the server, which in this case was invalid and returns an HTTP status code 502.

Browsers and servers interact using HTTP (HyperText Transfer Protocol) status codes. Whenever you access a URL, the browser sends an HTTP request to the web server of the website you are accessing. The server then returns a status code along with the requested resources.

HTTP status codes are grouped into five server responses:

1xx – informative

– informative 2xx – success

– Success 3xx – Redirect

– Redirect 4xx – Client error

– Client error 5xx – Server error

HTTP status codes beginning with the number “5” refer to errors that occur when there is a network error or communication problem between web servers.

Other 5xx status codes or server errors include 500 Internal Server Error, 501 Not Implemented, 503 Service Unavailable, and 504 Gateway Timeout. Although the exact reasons for each error vary, in most cases the root cause lies in the server.

Causes of 502 Bad Gateway Error

Before you can fix a 502 Bad Gateway error, you need to investigate the possible factors causing this error such as:

Unresolved domain name. This happens when a domain name doesn’t resolve to the correct IP. Keep in mind that if you recently migrated your domain name to a different host, it can take up to 24 hours for your DNS changes to be fully propagated and active.

Origin server overload. When an origin server runs out of resources, it can become overloaded and crash, throwing an HTTP 502 error. A sudden spike in traffic, low memory, and software timeouts are some of the most common causes of server overload.

browser error. Sometimes a browser displays a 502 error even though there are no server or network problems. In this case, the error can be triggered by faulty browser extensions like adblocker, outdated browser versions, or corrupted files in your browser cache.

Problems with home network equipment. If you’re encountering HTTP 502 errors on more than one website or browser, there’s a good chance your network devices are experiencing a temporary connectivity issue.

Firewall blocked. A firewall protects your website from suspicious traffic. However, some firewall systems are overly sensitive and may detect false positives. The system may be blocking a specific ISP or a request from a CDN.

How to Fix 502 Bad Gateway Error

Although the 502 Bad Gateway error is usually related to server-side issues, it can also be caused by misconfigurations or issues on the client side. Therefore, we will keep an eye on the most common troubleshooting steps considering both causes.

While some solutions focus on WordPress, most of them can be applied to any website.

1. Refresh the page

The first solution is pretty simple – wait a minute or two and refresh the page you’re on. In many cases, the error comes from a sudden increase in traffic.

Therefore, a simple page refresh is usually sufficient. For a shortcut, Windows users can press F5 or CTRL + F5, while Mac users can press CMD + R.

You can also try to check if the website is offline using an online tool like Website Planet or Host Tracker. This helps identify whether a server or client side issue is causing the error.

2. Clear the browser cache

If the error persists, chances are your browser cache has stored outdated and corrupted files. In this case, clearing the browser cache can fix the HTTP 502 Bad Gateway error.

Keep in mind that by removing cache you may lose important browsing data including bookmarks and preference settings. To prevent this, simply export your data from the browser and then import it again.

3. Try incognito mode

Accessing the website in Incognito mode is also a good idea as it will help determine if you are getting the HTTP 502 error message due to a browser-related issue. To open an incognito window, click the three dots button on your browser screen and select New Incognito Window.

If the error doesn’t appear in incognito mode, the problem might be caused by a browser extension.

Therefore, try disabling your add-ons or extensions gradually. Once you have deleted the one causing the error you should be able to access the website.

If disabling extensions doesn’t help, try opening a different browser. For example, if you currently use Google Chrome, try Mozilla Firefox.

If the page loads normally in the new browser, your previous browser could be causing the error. To solve the problem, try deleting and reinstalling your faulty browser.

4. Flush DNS

The 502 Bad Gateway error can also appear due to DNS issues like incorrect IP addresses and unresponsive DNS servers.

In this case, clearing your DNS cache may be the solution. This method works similar to clearing your browser cache. It removes corrupted files from your DNS server.

Temporarily changing your DNS servers is another step you can take. By default, your DNS servers are assigned by your ISP. However, you can always change it to a third-party server, e.g. B. Google Public DNS.

5. Test on another device

If none of the above solutions fixed HTTP error 502, test the connection on another computer or mobile device, preferably connected to a different network.

Try restarting your PC and other network devices. To do this, turn off your computer and disconnect your wireless router. Wait a moment and plug them back in.

This step will help decide if the error is related to your network device or if the problem lies elsewhere.

6. Check the error log

If you’re getting a 502 Bad Gateway error after a specific change or update, the error may be in your server itself. The best approach to this problem is to check your error log.

Typically, your hosting service grants access to enable website error logging through an admin dashboard. You can also enable error logging on your WordPress site by adding the following lines in wp-config.php:

define( ‘WP_DEBUG’, true ); define( ‘WP_DEBUG_LOG’, true ); define( ‘WP_DEBUG_DISPLAY’, false );

All generated errors are displayed in the wp-contents/debug.log file so you can identify which ones are causing a 502 Bad Gateway error.

7. Check plugins and themes

Sometimes faulty plugins or themes can be one of the reasons behind a 502 Bad Gateway error.

This is because poorly coded plugins and themes can conflict with each other. When this happens, your server stops every script and query on your website, rendering it inaccessible.

For some websites, the problem usually comes from caching or security plugins. There is a good chance that these plugins are blocking communication between servers, causing the error to persist.

If you don’t have a caching or security plugin installed but are still encountering an HTTP 502 error, your best bet is to disable and re-enable your plugins one at a time. To do this, go to Plugins and simply click Disable in the Bulk Actions menu.

Then activate each plugin while updating your WordPress site after each one. Once the 502 error pops up again, you have found the problem plugin.

However, if you cannot access your WordPress dashboard, you can try disabling them in your hosting panel or FTP program. Navigate to the wp-content directory and rename the plugins directory, for example plugins-disable.

If you are using Hostinger, access your hPanel and click Files. From there go to File Manager -> public_html -> wp-content.

Once your website is working after all plugins have been disabled, you can rename the folder back to Plugins. Then try enabling the plugins one by one to see which one caused the error in the first place.

If the website still doesn’t work, follow the same steps with your WordPress themes.

8. Check CDNs

Another cause of the 502 Bad Gateway errors can be problems with your CDN or DDoS mitigation services.

A content delivery network adds an extra layer between your server and your browser to deliver web content efficiently. However, this layer may encounter a problem connecting to your origin server, resulting in 502 errors.

A notable example would be Cloudflare, where the 502 Bad Gateway can come in two different flavors depending on the issue.

The above screen indicates that the issue is on Cloudflare’s side. In order to fix the problem, you need to contact the customer support team. Remember to check the Cloudflare System Status page beforehand.

Alternatively, you can disable Cloudflare, but keep in mind that your DNS propagation may take a few hours.

However, if you see the 502 Bad Gateway Cloudflare error shown above, it means that the problem lies with your current hosting provider. In this case, try contacting your web host’s support team and ask for assistance.

9. Check the site status

If you still get the 502 error despite trying most of the methods so far, it’s possible that the origin server is currently experiencing downtime.

Luckily, there are many tools on the web that you can use to check if a site is down, including Down for Everyone or Just Me and IsItDown. Just enter your URL and check the status of your website.

10. PHP max_execution_time and max_input_time

PHP timeout occurs when a PHP process loads longer than the specified max_execution_time or max_input_time. These are the values ​​set in your PHP configurations on your web server. Normally the values ​​are set to 300 seconds by default.

During the migration process, the migration process may time out, throwing the 502 Bad Gateway error. To fix this problem, you can talk to your web host to check what your values ​​are set to and if you can increase them.

If none of the above solutions fixed the 502 Bad Gateway error, your best bet is to contact their customer support team.

When describing the problem, try to include the troubleshooting steps you took. Provide as much information as possible and let the support team assist you.

502 Bad Gateway error variations

A 502 Bad Gateway error can appear in any browser, operating system, and service. However, its appearance varies in different ways. Here are some alternatives you might come across on the internet:

Temporary error (502)

502 error

Error 502

HTTP Error 502 Bad Gateway

502 Server Error: The server encountered a temporary error and could not complete your request

502 – The web server received an invalid response while acting as a gateway or proxy server

HTTP 502

502 proxy error

Bad 502 gateway

502 Service temporarily overloaded

502 Bad Gateway nginx

A blank white screen

Keep in mind that some websites or services have custom 502 error pages and look different, for example:

chrome

Chrome’s 502 Bad Gateway error screen tells you that the server encountered a transient error and was unable to complete your request. Chrome will also suggest trying again in 30 seconds. If the problem persists, try accessing the website from other browser windows.

GitLab

GitLab displays a 502 Bad Gateway error when its reverse proxy server doesn’t get a response from GitLab’s origin server for an extended period of time. The error page also provides instructions on how to resolve the issue.

Twitter

Twitter has its own way of indicating a 502 service temporarily overloaded error. It features a playful illustration with a clear message. Users can also check the Twitter status page for real-time data statistics.

How 502 Bad Gateway Error Affects SEO

A 502 error appears when your server encounters a network error that prevents it from completing a request. If this error occurs regularly and over a long period of time, it can negatively affect your website’s SEO.

If a requested page is not served, visitors are more likely to leave your site, resulting in a poor user experience. Also, the longer your website is down, the higher your bounce rate will be.

Similar to human visitors, search engine crawlers also consider a page with a 502 error to be broken, preventing them from indexing and ranking the page.

With this in mind, it is crucial for SEO reasons to investigate the factors that cause a 502 server error and fix it as soon as possible.

Error status codes similar to 502 Bad Gateway

Understanding error codes is important for website owners and developers to quickly identify and fix the problem. Aside from HTTP 502 errors, there are other status error codes that can appear on your website.

The most common include:

403 Forbidden Error . Occurs when the web server prevents visitors from accessing specific content.

Occurs when the web server prevents visitors from accessing specific content. 404 page not found . Refers to a response sent when the requested webpage is unavailable.

Refers to a response sent when the requested webpage is unavailable. 501 Not implemented. This indicates that the server does not have the functionality to fulfill a specific request.

This indicates that the server does not have the functionality to fulfill a specific request. 503 Service unavailable. This shows that the server is currently down for maintenance and cannot process the request.

This shows that the server is currently down for maintenance and cannot process the request. 504 Gateway timeout. Appears as a result of a proxy error when waiting too long for a response from another server.

Conclusion

A 502 Bad Gateway occurs when a server acting as a gateway receives an invalid response from the originating server. If left untreated, this error will affect your conversion rate, user experience, and page ranking.

As the status code suggests, the root of this error is usually on the server side. In other words, the problem isn’t coming from your website, internet connection, or your computer. With that in mind, it’s also important to keep an eye out for broken plugins or themes.

We hope these troubleshooting steps will help you fix any errors you might encounter and get your website back to a stable state. If you have any additional tips or solutions, feel free to share them with us in the comments below.

Was this guide helpful? Yes No

Various web servers, operating systems and browsers are used. For example, you may be using a Google Chrome browser and macOS. Another person, on the other hand, may be using Firefox and Windows 10 OS.

Additionally, some websites can customize the way the 502 Bad Gateway error is presented to users.

However, these variations all have the same meaning. A server acting as a gateway or proxy received an invalid response from an inbound server.

The most common ways you might see it are:

502 Bad Gateway error usually occurs when there are some network errors between computer and internet servers. This means that a server (not necessarily a web server) acting as a gateway or proxy received an invalid response from an upstream (or origin) server. In most cases the problem is not with your computer or your internet connection, it is much more likely that it is the website’s server instead.

HTTP status code

When you see the 502 Bad Gateway error, it is essentially an HTTP status code. HTTP status codes are three-digit codes and are divided into five different classes. The class of a status code can be recognized quickly by the first digit:

1xx: Informational 2xx: Successful 3xx: Redirect 4xx: Client error 5xx: Server error

The 502 Bad Gateway error comes from the server and usually has nothing to do with your PC. This usually happens when you visit a website that uses a relay point called a proxy server that separates data from the server hosting the website’s main page. If the main server and the proxy server fail to connect properly due to incorrect Transmission Control Protocol data, your browser determines that the proxy or gateway is faulty.

error messages

Various websites and services often customize their error messages, both to make them appear unique and to help tech-savvy users better understand the cause of the error.

502 Bad Gateway

502 proxy error

502. This is a mistake

HTTP Error 502 – Bad Gateway

502 Service temporarily overloaded

Bad Gateway: The proxy server received an invalid response from an upstream server

502 Server Error: The server encountered a temporary error and could not complete your request

Cause of 502 Bad Gateway error

The 502 Bad Gateway Error is an indication that something went wrong on your application’s server, as opposed to the client-side request. Basically, the cause is simple: Two online servers are having communication problems. Often simply refreshing or reloading the page (Ctrl-F5) is enough, but sometimes the problem can persist for days. There are 5 main issues that cause 502 Bad Gateway responses. These include:

Server failure: The gateway receives a negative result if the target server has completely failed. This can occur due to a system crash.

Domain name not resolvable: The domain name does not resolve to the correct IP or to no IP. It’s important to note that DNS changes can take just as long to be fully propagated and active globally. This depends on the TTL or lifetime defined per record.

Web server overload: If a web server reaches its limits and can no longer answer any queries, the gateway returns the status code 502 Bad Gateway.

Firewall blocks request: Firewalls can cause errors on both sides of the communication (server and client) when forwarding requests.

Browser errors: Browser extensions can also sometimes cause errors when displaying a website and generate a 502 error.

How to fix a 502 error

Error May 16, 2022 Nabilla R. 9min reading time

How to Fix 502 Bad Gateway Error

The reasons behind the 502 error can be numerous, from minor browser-related issues to problems with CDNs. This article describes some troubleshooting steps to follow when encountering a 502 Bad Gateway error, both on server and client side. We will also look at the different factors that can cause this error and the impact they can have on your website’s SEO.

Download e-book: Build your first website in 9 easy steps

Error Code 502 Bad Gateway Error Error Type Server Side Error Error Variations Temporary Error (502)

HTTP Error 502 Bad Gateway

502 proxy error

Bad 502 gateway

502 Service temporarily overloaded

A blank white screen error causes an unresolved domain name

Server overloaded

browser problems

Home network device error

Firewall blocked

How to Fix 502 Bad Gateway Error – Video Tutorial

Looking for a simple visual guide? Watch the video below.

Subscribe for more instructional videos! Hostinger Academy

What is a 502 Bad Gateway Error? The 502 Bad Gateway error indicates that the server you are connecting to received an invalid response. When visiting a URL, your browser sends an HTTP request to the server, which in this case was invalid and returns an HTTP status code 502.

Browsers and servers interact using HTTP (HyperText Transfer Protocol) status codes. Whenever you access a URL, the browser sends an HTTP request to the web server of the website you are accessing. The server then returns a status code along with the requested resources.

HTTP status codes are grouped into five server responses:

1xx – informative

– informative 2xx – success

– Success 3xx – Redirect

– Redirect 4xx – Client error

– Client error 5xx – Server error

HTTP status codes beginning with the number “5” refer to errors that occur when there is a network error or communication problem between web servers.

Other 5xx status codes or server errors include 500 Internal Server Error, 501 Not Implemented, 503 Service Unavailable, and 504 Gateway Timeout. Although the exact reasons for each error vary, in most cases the root cause lies in the server.

Causes of 502 Bad Gateway Error

Before you can fix a 502 Bad Gateway error, you need to investigate the possible factors causing this error such as:

Unresolved domain name. This happens when a domain name doesn’t resolve to the correct IP. Keep in mind that if you recently migrated your domain name to a different host, it can take up to 24 hours for your DNS changes to be fully propagated and active.

Origin server overload. When an origin server runs out of resources, it can become overloaded and crash, throwing an HTTP 502 error. A sudden spike in traffic, low memory, and software timeouts are some of the most common causes of server overload.

browser error. Sometimes a browser displays a 502 error even though there are no server or network problems. In this case, the error can be triggered by faulty browser extensions like adblocker, outdated browser versions, or corrupted files in your browser cache.

Problems with home network equipment. If you’re encountering HTTP 502 errors on more than one website or browser, there’s a good chance your network devices are experiencing a temporary connectivity issue.

Firewall blocked. A firewall protects your website from suspicious traffic. However, some firewall systems are overly sensitive and may detect false positives. The system may be blocking a specific ISP or a request from a CDN.

How to Fix 502 Bad Gateway Error

Although the 502 Bad Gateway error is usually related to server-side issues, it can also be caused by misconfigurations or issues on the client side. Therefore, we will keep an eye on the most common troubleshooting steps considering both causes.

While some solutions focus on WordPress, most of them can be applied to any website.

1. Refresh the page

The first solution is pretty simple – wait a minute or two and refresh the page you’re on. In many cases, the error comes from a sudden increase in traffic.

Therefore, a simple page refresh is usually sufficient. For a shortcut, Windows users can press F5 or CTRL + F5, while Mac users can press CMD + R.

You can also try to check if the website is offline using an online tool like Website Planet or Host Tracker. This helps identify whether a server or client side issue is causing the error.

2. Clear the browser cache

If the error persists, chances are your browser cache has stored outdated and corrupted files. In this case, clearing the browser cache can fix the HTTP 502 Bad Gateway error.

Keep in mind that by removing cache you may lose important browsing data including bookmarks and preference settings. To prevent this, simply export your data from the browser and then import it again.

3. Try incognito mode

Accessing the website in Incognito mode is also a good idea as it will help determine if you are getting the HTTP 502 error message due to a browser-related issue. To open an incognito window, click the three dots button on your browser screen and select New Incognito Window.

If the error doesn’t appear in incognito mode, the problem might be caused by a browser extension.

Therefore, try disabling your add-ons or extensions gradually. Once you have deleted the one causing the error you should be able to access the website.

If disabling extensions doesn’t help, try opening a different browser. For example, if you currently use Google Chrome, try Mozilla Firefox.

If the page loads normally in the new browser, your previous browser could be causing the error. To solve the problem, try deleting and reinstalling your faulty browser.

4. Flush DNS

The 502 Bad Gateway error can also appear due to DNS issues like incorrect IP addresses and unresponsive DNS servers.

In this case, clearing your DNS cache may be the solution. This method works similar to clearing your browser cache. It removes corrupted files from your DNS server.

Temporarily changing your DNS servers is another step you can take. By default, your DNS servers are assigned by your ISP. However, you can always change it to a third-party server, e.g. B. Google Public DNS.

5. Test on another device

If none of the above solutions fixed HTTP error 502, test the connection on another computer or mobile device, preferably connected to a different network.

Try restarting your PC and other network devices. To do this, turn off your computer and disconnect your wireless router. Wait a moment and plug them back in.

This step will help decide if the error is related to your network device or if the problem lies elsewhere.

6. Check the error log

If you’re getting a 502 Bad Gateway error after a specific change or update, the error may be in your server itself. The best approach to this problem is to check your error log.

Typically, your hosting service grants access to enable website error logging through an admin dashboard. You can also enable error logging on your WordPress site by adding the following lines in wp-config.php:

define( ‘WP_DEBUG’, true ); define( ‘WP_DEBUG_LOG’, true ); define( ‘WP_DEBUG_DISPLAY’, false );

All generated errors are displayed in the wp-contents/debug.log file so you can identify which ones are causing a 502 Bad Gateway error.

7. Check plugins and themes

Sometimes faulty plugins or themes can be one of the reasons behind a 502 Bad Gateway error.

This is because poorly coded plugins and themes can conflict with each other. When this happens, your server stops every script and query on your website, rendering it inaccessible.

For some websites, the problem usually comes from caching or security plugins. There is a good chance that these plugins are blocking communication between servers, causing the error to persist.

If you don’t have a caching or security plugin installed but are still encountering an HTTP 502 error, your best bet is to disable and re-enable your plugins one at a time. To do this, go to Plugins and simply click Disable in the Bulk Actions menu.

Then activate each plugin while updating your WordPress site after each one. Once the 502 error pops up again, you have found the problem plugin.

However, if you cannot access your WordPress dashboard, you can try disabling them in your hosting panel or FTP program. Navigate to the wp-content directory and rename the plugins directory, for example plugins-disable.

If you are using Hostinger, access your hPanel and click Files. From there go to File Manager -> public_html -> wp-content.

Once your website is working after all plugins have been disabled, you can rename the folder back to Plugins. Then try enabling the plugins one by one to see which one caused the error in the first place.

If the website still doesn’t work, follow the same steps with your WordPress themes.

8. Check CDNs

Another cause of the 502 Bad Gateway errors can be problems with your CDN or DDoS mitigation services.

A content delivery network adds an extra layer between your server and your browser to deliver web content efficiently. However, this layer may encounter a problem connecting to your origin server, resulting in 502 errors.

A notable example would be Cloudflare, where the 502 Bad Gateway can come in two different flavors depending on the issue.

The above screen indicates that the issue is on Cloudflare’s side. In order to fix the problem, you need to contact the customer support team. Remember to check the Cloudflare System Status page beforehand.

Alternatively, you can disable Cloudflare, but keep in mind that your DNS propagation may take a few hours.

However, if you see the 502 Bad Gateway Cloudflare error shown above, it means that the problem lies with your current hosting provider. In this case, try contacting your web host’s support team and ask for assistance.

9. Check the site status

If you still get the 502 error despite trying most of the methods so far, it’s possible that the origin server is currently experiencing downtime.

Luckily, there are many tools on the web that you can use to check if a site is down, including Down for Everyone or Just Me and IsItDown. Just enter your URL and check the status of your website.

10. PHP max_execution_time and max_input_time

PHP timeout occurs when a PHP process loads longer than the specified max_execution_time or max_input_time. These are the values ​​set in your PHP configurations on your web server. Normally the values ​​are set to 300 seconds by default.

During the migration process, the migration process may time out, throwing the 502 Bad Gateway error. To fix this problem, you can talk to your web host to check what your values ​​are set to and if you can increase them.

If none of the above solutions fixed the 502 Bad Gateway error, your best bet is to contact their customer support team.

When describing the problem, try to include the troubleshooting steps you took. Provide as much information as possible and let the support team assist you.

502 Bad Gateway error variations

A 502 Bad Gateway error can appear in any browser, operating system, and service. However, its appearance varies in different ways. Here are some alternatives you might come across on the internet:

Temporary error (502)

502 error

Error 502

HTTP Error 502 Bad Gateway

502 Server Error: The server encountered a temporary error and could not complete your request

502 – The web server received an invalid response while acting as a gateway or proxy server

HTTP 502

502 proxy error

Bad 502 gateway

502 Service temporarily overloaded

502 Bad Gateway nginx

A blank white screen

Keep in mind that some websites or services have custom 502 error pages and look different, for example:

chrome

Chrome’s 502 Bad Gateway error screen tells you that the server encountered a transient error and was unable to complete your request. Chrome will also suggest trying again in 30 seconds. If the problem persists, try accessing the website from other browser windows.

GitLab

GitLab displays a 502 Bad Gateway error when its reverse proxy server doesn’t get a response from GitLab’s origin server for an extended period of time. The error page also provides instructions on how to resolve the issue.

Twitter

Twitter has its own way of indicating a 502 service temporarily overloaded error. It features a playful illustration with a clear message. Users can also check the Twitter status page for real-time data statistics.

How 502 Bad Gateway Error Affects SEO

A 502 error appears when your server encounters a network error that prevents it from completing a request. If this error occurs regularly and over a long period of time, it can negatively affect your website’s SEO.

If a requested page is not served, visitors are more likely to leave your site, resulting in a poor user experience. Also, the longer your website is down, the higher your bounce rate will be.

Similar to human visitors, search engine crawlers also consider a page with a 502 error to be broken, preventing them from indexing and ranking the page.

With this in mind, it is crucial for SEO reasons to investigate the factors that cause a 502 server error and fix it as soon as possible.

Error status codes similar to 502 Bad Gateway

Understanding error codes is important for website owners and developers to quickly identify and fix the problem. Aside from HTTP 502 errors, there are other status error codes that can appear on your website.

The most common include:

403 Forbidden Error . Occurs when the web server prevents visitors from accessing specific content.

Occurs when the web server prevents visitors from accessing specific content. 404 page not found . Refers to a response sent when the requested webpage is unavailable.

Refers to a response sent when the requested webpage is unavailable. 501 Not implemented. This indicates that the server does not have the functionality to fulfill a specific request.

This indicates that the server does not have the functionality to fulfill a specific request. 503 Service unavailable. This shows that the server is currently down for maintenance and cannot process the request.

This shows that the server is currently down for maintenance and cannot process the request. 504 Gateway timeout. Appears as a result of a proxy error when waiting too long for a response from another server.

Conclusion

A 502 Bad Gateway occurs when a server acting as a gateway receives an invalid response from the originating server. If left untreated, this error will affect your conversion rate, user experience, and page ranking.

As the status code suggests, the root of this error is usually on the server side. In other words, the problem isn’t coming from your website, internet connection, or your computer. With that in mind, it’s also important to keep an eye out for broken plugins or themes.

We hope these troubleshooting steps will help you fix any errors you might encounter and get your website back to a stable state. If you have any additional tips or solutions, feel free to share them with us in the comments below.

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A gateway is a network node used in telecommunications that connects two networks with different transmission protocols. Gateways serve as the entry and exit points for a network, as all data must pass through or communicate with the gateway before being forwarded. In most IP-based networks, the only traffic that does not pass through at least one gateway is traffic flowing between nodes on the same local area network (LAN) segment. The term default gateway or network gateway can also be used to describe the same concept.

The main benefit of using a gateway in personal or corporate scenarios is to simplify internet connection in one device. In the enterprise, a gateway node can also act as a proxy server and firewall. Gateways can be purchased through well-known technology retailers such as Best Buy, or rented through an ISP.

How gateways work All networks have a boundary that restricts communication to devices that are directly connected to it. Therefore, if a network wants to communicate with devices, nodes or networks outside this boundary, they need the functionality of a gateway. A gateway is often referred to as a combination of a router and a modem. The gateway is implemented at the edge of a network and manages all data routed internally or externally from that network. When one network wants to communicate with another, the data packet is forwarded to the gateway and then routed to the destination via the most efficient path. In addition to routing data, a gateway also stores information about the internal paths of the host network and the paths of any additional networks encountered. Gateways are basically protocol converters that facilitate compatibility between two protocols and operate at any level of the OSI (Open Systems Interconnection) model. One use for gateways is to provide a communication link between an IoT environment and the cloud.

Types of Gateways Gateways can take many forms and serve a variety of purposes. Examples include: Web application firewalls – This type filters traffic to and from a web server and inspects application layer data.

Cloud Storage Gateways – This type translates storage requests using various cloud storage service API calls. It enables companies to integrate storage from a private cloud into applications without migrating to a public cloud.

API, SOA, or XML gateways – This type manages the traffic flowing in and out of a service, microservices-oriented architecture, or XML-based web service.

IoT gateways – This type aggregates sensor data from devices in an IoT environment, translates between sensor protocols, and processes sensor data before sending it onward.

Media gateways – This type converts data from the format required for one type of network to the format required for another.

Email security gateways – This type prevents the transmission of emails that violate company policies or transmit information with malicious intent.

VoIP Trunk Gateways – This type facilitates the use of plain old telephone service equipment such as landline telephones and fax machines with a Voice over IP (VoIP) network. In addition, a service provider can develop its own personal gateways for use by customers. For example, Amazon Web Services (AWS) has an Amazon API Gateway that allows a developer to connect non-AWS applications to AWS backend resources.

HTTP 502 Status Code (Bad Gateway)

An HTTP status code of 502 (Bad Gateway) indicates that CloudFront couldn’t serve the requested object because it couldn’t connect to the origin server.

SSL/TLS negotiation failure between CloudFront and a custom origin server

If you’re using a custom origin and have configured CloudFront to require HTTPS between CloudFront and your origin, the problem might be domain name mismatches. The SSL/TLS certificate installed on your origin contains a domain name in the Common Name field and possibly several more in the Subject Alternative Names field. (CloudFront supports wildcard characters in certificate domain names.) One of the domain names in the certificate must match one or both of the following values:

The value that you specified for the origin domain name for the corresponding origin in your distribution.

The value of the host header if you configured CloudFront to forward the host header to your origin. For more information on forwarding the host header to your origin, see Content caching based on request headers.

If the domain names do not match, the SSL/TLS handshake fails and CloudFront returns an HTTP status code 502 (Bad Gateway) and sets the X-Cache header to Error from cloudfront .

To determine if domain names in the certificate match the originating domain name in the distribution or the host header, you can use an online SSL checker or OpenSSL. If the domain names don’t match, you have two options:

Obtain a new SSL/TLS certificate that includes the appropriate domain names. If you use AWS Certificate Manager (ACM), see Requesting a Public Certificate in the AWS Certificate Manager User Guide for more information about requesting a new certificate.

Change the distribution configuration so that CloudFront no longer attempts to use SSL to connect to your origin.

Online SSL Checker

To find an SSL testing tool, search the web for “online ssl checker”. Typically, you provide your domain name and the tool will return a variety of information about your SSL/TLS certificate. Confirm that the certificate contains your domain name in the Common Name or Subject Alternative Names fields.

OpenSSL

To troubleshoot CloudFront HTTP 502 errors, you can use OpenSSL to attempt to establish an SSL/TLS connection to your origin server. If OpenSSL is unable to connect, it may indicate a problem with your origin server’s SSL/TLS configuration. If OpenSSL is able to connect, it returns information about the origin server’s certificate, including the certificate’s common name (Subject CN field) and subject alternative name (Subject Alternative Name field).

Use the following OpenSSL command to test the connection to your origin server (replace the origin domain name with the domain name of your origin server, e.g. example.com):

openssl s_client -connect origin domain name: 443

If the following applies:

Your origin server supports multiple domain names with multiple SSL/TLS certificates

Your distribution is configured to forward the host header to the origin

Then add the -servername option to the OpenSSL command, as in the following example (replace CNAME with the CNAME configured in your distribution):

openssl s_client – connect origin domain name: 443 – server name CNAME

Origin not responding with supported ciphers/protocols

CloudFront connects to origin servers using ciphers and protocols. For a list of the ciphers and protocols supported by CloudFront, see Supported Protocols and Ciphers Between CloudFront and the Origin. If your origin doesn’t respond with one of these ciphers or protocols in the SSL/TLS exchange, CloudFront can’t connect. You can verify that your origin supports the ciphers and protocols using an online tool such as SSL Labs. Enter your originating domain name in the Hostname field, then select Submit. Review the Common Names and Alternate Names fields from the test to see if they match your originating domain name. After the test is complete, locate the Protocols and Ciphersuites sections of the test results to see what ciphers or protocols are supported by your origin. Compare them to the list of supported protocols and ciphers between CloudFront and the origin.

The SSL/TLS certificate at the origin is expired, invalid, self-signed, or the certificate chain is out of order

If the origin server returns the following, CloudFront drops the TCP connection, returns HTTP status code 502 (Bad Gateway), and sets the X-Cache header to Error from cloudfront :

An expired certificate

Invalid certificate

Self-Signed Certificate

Certificate chain in the wrong order

Note If the full certificate chain, including the intermediate certificate, is not present, CloudFront drops the TCP connection.

For information about installing an SSL/TLS certificate on your custom origin, see Require HTTPS for Communication Between CloudFront and Your Custom Origin.

Origin does not respond to specified ports in Origin settings

When you create an origin in your CloudFront distribution, you can specify the ports that CloudFront uses to connect to the origin for HTTP and HTTPS traffic. By default, this is TCP 80/443. You have the option to change these ports. If your origin denies traffic on those ports for any reason, or if your backend server doesn’t respond on the ports, CloudFront can’t connect.

To fix these issues, check any firewalls running in your infrastructure and make sure they are not blocking the supported IP ranges. For more information, see AWS IP Address Ranges in the Amazon Web Services General Reference. Also, verify that your web server is running on the origin.

CloudFront couldn’t resolve your domain of origin due to DNS issues

When CloudFront receives a request for an object that has expired or is not in its cache, it sends a request to the origin to get the updated object. To make a successful request to the origin, CloudFront performs DNS resolution on the origin domain name. However, if there are problems with the DNS service hosting your domain, CloudFront cannot resolve the domain name to get the IP address, resulting in a 502 error. To resolve this issue, contact your DNS provider or see If you’re using Amazon Route 53, why can’t I access my website that’s using Route 53 DNS services?

To further troubleshoot this issue, ensure that the authoritative nameservers of the root domain or zone apex of your origin (e.g. example.com ) are working properly. Your authoritative name servers then receive the request and return the IP address associated with the domain and identical to the DNS servers you used to set up your CloudFront distribution. Use the following commands to find the nameservers for your Apex origin:

dig OriginAPEXDomainName NS +short nslookup -query=NS OriginAPEXDomainName

Once you have the names of your nameservers, use the following commands to query your origin’s domain name against them to make sure everyone responds with an answer:

dig OriginDomainName @NameServerFromAbove nslookup OriginDomainName NameServerFromAbove

Lambda@Edge function validation error

When using Lambda@Edge, an HTTP 502 status code can indicate that your Lambda function response was malformed or contained invalid content. For more information on troubleshooting Lambda@Edge errors, see Testing and Debugging Lambda@Edge Functions.

If you’ve ever visited a website that gave you an error page, you know how frustrating it is.

One of the worst things you can do as a brand is not to meet the needs and expectations of your audience. If your website visitors see an error page when looking for help or information, they could become frustrated and lose trust in your brand, permanently damaging your reputation.

The 504 Gateway Timeout Error is a type of error that can affect user experience in this way. To help you not lose brand sentiment and consumer confidence, we have explained exactly what this error means and what are its most common causes and solutions.

What is a 504 gateway timeout error? A 504 gateway timeout error means your web server didn’t get a timely response from another upstream server when it tried to load one of your web pages. Simply put, your web servers aren’t communicating with each other fast enough. Since a 504 gateway timeout error is rather generic, it doesn’t indicate the exact cause of the problem. In this case, your website will show your website visitors an error webpage.

This is how a 504 gateway timeout error can appear in your user’s browser:

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504 error wording

The screenshot above shows how a 504 gateway timeout error is displayed on a server. Below are some other common ways a 504 error can appear, depending on the server, operating system, or browser you’re using.

A 504 error is displayed as HTTP ERROR 504 in Google Chrome. This code appears below a message that reads something like “This website cannot be reached. _____ took too long to reply.”

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In Windows-based programs, a 504 error is displayed as ERROR 504, HTTP_STATUS_GATEWAY_TIMEOUT, or “Request timed out waiting for a gateway message.” This is what it can look like when using Excel:

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During a Windows update, a gateway timeout error generates error code 0x80244023. The message is: WU_E_PT_HTTP_STATUS_GATEWAY_TIMEOUT.

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In other operating systems, web servers, or browsers, a 504 error may also result in the following message – although this is less common: “The proxy server did not receive a timely response from the upstream server.” Here’s a slight variation:

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So now we know how the 504 error is worded, but what exactly does it mean? Let’s decode it below.

What does 504 gateway timeout mean?

When you visit a website, your server sends a request to another server hosting that website. This server – known as the “upstream server” – receives the request and responds with all the resources needed to load the website in your browser.

However, a 504 gateway timeout error means your server didn’t get a response from the upstream server fast enough. Because its request has timed out, your server cannot load the webpage and ultimately fulfill its role as a gateway – hence the name “Gateway Timeout” error.

You may be wondering what exactly is causing the delay in the upstream server’s response – and that’s a good question. Let’s get into that below.

504 gateway timeout causes

504 gateway timeout errors are among the most frustrating HTTP status codes you can get. They indicate what happened to your website, but they don’t tell you why it happened, making it difficult for you to pinpoint the cause and ultimately fix the problem.

Below are a few options.

Server connectivity issues

Most websites are on multiple servers or third-party hosting providers. If your server is down for maintenance or other reasons, your website might show visitors a 504 gateway timeout error page.

DNS changes

If you recently changed servers or moved your website to a different IP address, changes will be made to your website’s DNS server. This could result in your website serving a 504 Gateway Timeout Error page to its visitors. Your website will not be operational until these DNS changes take full effect, which may take a few hours.

Incorrect firewall configurations

Your firewall is your website’s gatekeeper, protecting your website from malicious visitors or distributed denial-of-service (DDoS) attacks. Sometimes, a bad firewall configuration causes your firewall to consider requests from a content delivery network as an attack on your server and reject them, resulting in a 504 Gateway Timeout Error.

Error in your website code

If your website’s code contains an error, your server may not be able to correctly answer requests from a content delivery network.

Network connection error

Since a 504 error is the result of a timeout while processing a request between servers, the problem is likely with them – not the internet connection or the user’s device. However, if just one user reports seeing a 504 error on your site, it could be with their modem, router, or other device. or your internet connection.

Because there can be multiple reasons for a 504 error to appear, it’s ultimately up to you to rule out each one until you find the real cause. Luckily, there are five common and effective solutions to fix most of the causes of 504 gateway timeout errors.

How to fix 504 gateway timeout errors Check for server connection issues. Look for DNS changes. Search your logs. Fix faulty firewall configurations. Comb your site’s code to find errors. Contact your hosting provider.

1. Check for server connection issues.

If your server is down for maintenance or other reasons, your website will likely present visitors with a 504 Gateway Timeout Error page. The only way to fix this problem is to wait for your server to finish maintenance or fix the problem that is causing the error.

2. Look for DNS changes.

If you’ve recently switched hosting providers or moved your website to a different IP address, your website’s DNS server needs to be updated. These DNS changes take a few hours to process, so your website may be showing visitors a 504 gateway timeout error page in the meantime. The only solution is to sit still while these DNS changes take effect.

3. Search your logs.

If the problem isn’t with your server’s connection or DNS information, look at your server logs. These logs contain details about the health and status of your server. Searching them might uncover other issues that could be causing a 504 error.

4. Correct incorrect firewall configurations.

A faulty firewall configuration can be the reason for your 504 gateway timeout error. To rule this out as a cause, you can temporarily disable your firewall.

If your device is running Windows, go to your Control Panel and click Update & Security > Windows Security > Virus & Threat Protection > Manage Settings. On this settings page you can disable your firewall.

If your device runs on Mac OS, simply navigate to System Preferences > Security & Privacy > Firewall to disable it.

After disabling your firewall, check if the 504 error is resolved. If this is the case, you can either reconfigure the settings of your existing antivirus or switch to a new one.

If the error is not resolved, don’t forget to re-enable your firewall before proceeding to the next step.

5. Comb your site’s code to find errors.

Comb your code to find bugs or copy your code to a development machine. It runs a thorough debugging process that simulates the situation where your 504 gateway timeout error occurred and allows you to see the exact moment when something went wrong.

6. Contact your hosting provider.

Contacting your hosting provider should be the last resort. But if you’ve tried the steps above and still see the 504 gateway timeout error, they might be able to solve the problem or provide valuable insights.

How 504 gateway timeout errors affect SEO

Fixing a 504 gateway timeout error can take time—but it’s worth it when you consider how it can affect your site’s technical SEO.

Like an internal HTTP server error 500, 503 error, or any other 5xx error, a 504 gateway timeout error will prevent your website from loading. This not only harms the user experience but also your SEO performance.

If a web crawler tries to crawl one of your pages and gets a 504 error, it can’t crawl the page. If this page has already been indexed, it may move down in search engine results. Or it could be deindexed if the error persists.

Fixing the 504 gateway timeout error

There is no foolproof way to prevent 504 gateway timeout errors on your website, but there are steps you can take to fix them. By fixing this error as soon as possible, you ensure that visitors continue to have a seamless experience on your website and mitigate any negative impact on your SEO.

Editor’s Note: This post was originally published in January 2019 and has been updated for completeness.