How Do I Bypass Bad Gateway 502? Best 179 Answer

A 502 Bad Gateway Error occurs when you try to visit a web page but one web server receives an invalid response from another. Usually the problem is with the website itself and there is nothing you can do about it. In other cases, this error occurs due to a problem with your computer or network equipment.

What is a 502 Bad Gateway Error?

A 502 Bad Gateway Error means that the web server you connected to was acting as a proxy to relay information from another server, but received a bad response from that other server. It’s called a 502 error because that’s the HTTP status code that the web server uses to describe this type of error.

These bad reactions can be due to a number of different causes. The server may be overloaded or there may be network problems between the two servers and the problem is only temporary. It is also possible that there is a misconfigured firewall or even a coding error and the issue will not be resolved until these issues are resolved.

Just like 404 errors, website designers can customize the look of a 502 error. So you may see different looking 502 pages on different websites. Sites may also use slightly different names for this error. For example, you may see things like:

HTTP Error 502 Bad Gateway

HTTP 502

502 Service temporarily overloaded

Temporary error (502)

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

502 Bad Gateway nginx

In the vast majority of cases, this is just a bug on the server side of things that you can’t do anything about. Sometimes it’s a temporary bug; sometimes it isn’t. Still, there are some things you can try on your end of things.

Reload the page

Refreshing the page is always worth trying. Often the 502 error is temporary, and a simple update might do the trick. Most browsers allow you to refresh the page by pressing Ctrl+R on Windows or Cmd+R on Mac, and also provide a refresh button somewhere in the address bar.

It doesn’t fix the issue very often, but it only takes a second to try.

Check if the site is unavailable to other people

If you can’t reach a website (for whatever reason), you can also check if it’s just you having a connection problem or if other people are having the same problems. There are many tools for this, but our favorites are isitdownrightnow.com and downforeveryoneorjustme.com. Both work pretty much the same. Enter the URL you want to check and you will get a result like this.

If you get a report saying the website is down for everyone, there’s not much you can do except try again later. If the report shows the site is up, the problem may be yours. It’s very rare for this to happen with a 502 error, but it’s possible and you can try some of the things we describe in the next few sections.

Try a different browser

It’s possible that a problem with your browser is causing the 502 Bad Gateway error. An easy way to check this is to use a different browser and see if it works. You can use Google Chrome, Mozilla Firefox, Apple Safari or Microsoft Edge. If you can still see the error in the new browser, then you know it’s not a browser issue and you should try a different solution.

Clear your browser’s cache and cookies

If trying a different browser works, your main browser may have cached outdated or corrupted files that could be causing the 502 error. Removing these cached files and trying to open the website might solve the problem.

It’s definitely worth trying, and we have a handy guide for you on how to clear your history on any browser.

RELATED: How to Clear Your History in Any Browser

Check your plugins and extensions

If you are using extensions in your browser, it is possible that one or more of the extensions are causing the problem. Try disabling all your extensions and then accessing the website. If the error goes away after that, it’s likely that a plugin is causing the problem. Activate your plugins one by one to find the culprit.

RELATED: How to Uninstall Extensions in Chrome, Firefox, and Other Browsers

Reboot your devices

So you’ve used a website verification tool and discovered that the website isn’t available to you. And you have tested another browser and have the same problem. So you know the problem is probably yours, but it’s not your browser.

It’s possible that there are some strange, temporary problems with your computer or network equipment (wireless LAN, router, modem, etc.). A simple restart of your computer and network devices may help resolve the issue.

Change your DNS servers

Sometimes DNS problems can cause 502 errors. Changing your DNS servers is not a likely solution, but it is a possible one. And it’s not too difficult to do. Unless you’ve changed them yourself, your DNS servers are likely set by your ISP. You can change them to a third party DNS server like OpenDNS or Google DNS and that might solve the problem.

And there are other reasons why you might want to change DNS servers too – such as: B. higher speed and reliability.

RELATED: The Ultimate Guide to Changing Your DNS Server

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.

The 504 gateway timeout error is one of the most common HTTP 5xx errors that website owners and website visitors face. For many WordPress blogs and ecommerce platforms, knowing how to fix server errors like this one is crucial to keep their hard-earned visitors from going to competitor websites.

Because the 504 Gateway Timeout error doesn’t tell you why it occurred, it’s difficult to pinpoint exactly what’s causing the server timeout. This article will help you understand it in detail, learn how to diagnose its cause and then fix it.

After trying all the different solutions mentioned in the post, your website should be up and running in no time.

Sounds interesting? Let’s dive in!

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The 504 gateway timeout error is one of the most common HTTP 5xx errors that website owners and website visitors face. 🤔 Learn how to fix the problem quickly with this guide. ⬇️

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What is the 504 gateway timeout error?

Every time you visit a website in your browser, the browser sends a request to the web server hosting the website. The server processes the request and responds with the requested resources.

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The server response includes one of many HTTP status codes to indicate the status of the response to the browser. But not all of these HTTP status codes are errors. For example, a status code of 200 OK means that the server successfully processed the request and “everything is fine”.

The 5xx class of HTTP status codes indicates that something is wrong with the server, the server is aware of it and cannot complete the client request. Therefore, they are also known as Server Error 5xx status codes.

Officially, five status codes are given under the 5xx class (500, 501, 502, 503, 504). You may also encounter many unofficial codes (506, 507, 509, 520, etc.).

The Internet Engineering Task Force (IETF) defines the 504 Gateway Timeout error as follows:

The 504 (Gateway Timeout) status code indicates that the server, while acting as a gateway or proxy, did not receive a timely response from an upstream server it needed to access to complete the request.

To simplify further, this error occurs when two servers are involved in processing a request. The first server (usually the main server) expires and waits for a response from the second server (upstream server).

The 504 gateway timeout error manifests itself in various forms. Here are a few ways it usually appears:

The 504 Gateway Timeout error is similar to the 502 Bad Gateway error, which indicates that the first server received an invalid response from the second (upstream) server.

Variations of the 504 gateway timeout error

The browser shows every 504 gateway timeout error in it, just like any other error. Since there are different operating systems, web servers, browsers and user agents, it can appear in different ways.

Below are some common variants of 504 error messages you may encounter:

504 Gateway timeout

504 gateway timeout NGINX

NGINX 504 gateway timeout

Gateway timeout error

Error 504

HTTP error 504

HTTP Error 504 – Gateway Timeout

HTTP 504

504 error

Gateway timeout (504)

This page isn’t working – The domain took too long to respond

504 Gateway Timeout – The server did not respond in time

The page request was canceled because it took too long to execute

Website visitor: There was a problem processing your request. Please try again in a few minutes.

Site owner: Gateway timed out. Check your error log for more information.

A blank white screen

All of the above error responses, although worded differently, point to the same 504 gateway timeout server error.

Web servers and websites can customize how they present the 504 gateway timeout error to users. Some of them can be cool! It’s an excellent tactic to quell the disappointment of your visitors.

SEO impact of 504 gateway timeout error

All 5xx errors prevent a web page from loading, thereby adversely affecting the user experience. Therefore, search engines like Google take these errors seriously. If the error persists for a long period of time, it can even result in the website being removed from search engine results.

For example, when Google spiders come across a 503 Service Unavailable error, they will understand that it is a temporary issue as it is mainly used to enable website maintenance mode. Therefore, they try to crawl the page again later.

A 504 gateway timeout error is not necessarily temporary as it can have multiple reasons. If your site is down for just a few minutes and the spiders try to crawl it several times a minute, they try to serve the page from their cache. You wouldn’t even notice.

However, if your site is down for more than 6 hours or more, Google considers the 504 error to be a serious site-wide issue that you need to fix as soon as possible. This can negatively impact your SEO.

Google Search Console is one of the best SEO tools for monitoring your website’s HTTP 5xx errors.

Causes of 504 gateway timeout error

Since the 504 error is due to a timeout between servers, the problem is probably not with the client’s device or internet connection. This includes your device and connection.

A 504 gateway timeout error indicates that the web server is waiting too long for a response from another server and is “timed out”. This timeout can have many reasons: The other server is not working properly, is overloaded or is down.

The other server does not always have to be external (e.g. CDN, API gateway). It can also be a server-like entity within the main web server (e.g. reverse proxy server, database server).

How to fix 504 gateway timeout error

Without knowing exact details about the WordPress site such as: B. the server configuration, hosting plan, third-party plugins and the traffic it attracts, you may find it frustrating and overwhelming to troubleshoot a 504 gateway timeout error.

Because there are many variables involved, I recommend that you start by troubleshooting client-side issues, which are fairly rare, and then move on to troubleshooting server-side issues. They are usually the culprits with 504 errors.

Try reloading the webpage

One of the first things to try when encountering a 504 gateway timeout error is to wait a few minutes and try refreshing the page.

You can press the F5 key combination to refresh/reload the webpage in most browsers. To clear the page’s browser cache before reloading, you can press CTRL+F5 instead.

While you’re at it, you can also try loading the website in a different browser to rule this out as a problem. Since most 504 errors are due to temporarily overloaded servers, using this solution should get your website working again right away.

If waiting and reloading the website doesn’t fix the 504 error problem, you can check if a website is down for everyone or just you. Two useful online tools for testing a website for downtime are Down for Everyone or Just Me and Is It Down Right Now?

Restart your network devices

Sometimes problems with your network devices like modem or router can cause 504 gateway timeout error. Restarting these devices might help you fix the problem.

While you can turn off all of these network devices in any order, the order in which you turn them back on is important. Typically turn these devices on from the “outside in” by following the ISP’s connection order to your main client device.

Check your proxy settings

A proxy server sits between your device and the internet. It is mainly used to improve online privacy by hiding private information (e.g. device location) from websites and web servers (e.g. using a VPN).

Although it is rare for proxy servers to cause a 504 error, sometimes incorrect proxy server settings can be the culprit. You can disable the proxy server and try reloading the webpage to see if that fixes the error.

Most clients do not use a proxy service, so you can skip this step if you are sure you are not using a proxy server. However, you may have set it without even knowing it. I would suggest that you check your device and browser proxy settings to rule out this cause.

DNS problems

A 504 gateway timeout error can also be caused by DNS issues on the server side or the client side (or both).

The most likely reason for a server-side DNS problem is that the FQDN (fully qualified domain name) does not resolve to the correct IP address, or the DNS server is not responding. Usually this occurs when you have just migrated your WordPress site to a new server or host. Therefore, it is important to wait until the domain’s DNS records are fully propagated, which can take up to 24 hours.

You can use free tools like whatsmydns.net DNS Checker or DNSMap to see if your DNS has spread worldwide.

To troubleshoot client-side DNS issues, you can try flushing your local DNS cache. It’s like clearing your browser cache, except here you’re flushing the DNS cache from the operating system.

If you are using Windows, you can flush DNS cache by opening Command Prompt and typing the following statement:

ipconfig /flushdns

You should see the message “DNS resolver cache flushed successfully”. message if it worked.

For the latest macOS versions, you can open the terminal and run the following command:

sudo killall -HUP mDNSResponder

You won’t see a notification in macOS when the process is complete, but you can change this by appending the command with your custom message.

sudo killall -HUP mDNSResponder; DNS cache was cleared successfully

If you’re using older versions of macOS, the command you need to enter will vary depending on which version of macOS you’re running. For more details, see the macOS section in Kinsta’s in-depth flush DNS tutorial.

If you are using the Linux operating system, the process is quite similar to macOS as even Linux uses the terminal as a command line interface. Because there are many Linux distributions, the exact command you need to run may vary from one distribution to another. For more information, see Kinsta’s guide.

Finally, you can temporarily change your client-side DNS servers. By default, your ISP assigns you the DNS servers automatically. However, you can temporarily change these to public DNS IPs.

Some reliable DNS servers you can try are Google Public DNS, Cloudflare 1.1.1.1, Quad9 DNS, and Cisco OpenDNS.

Temporarily disable your website’s CDN

Sometimes the problem could also be with your Content Delivery Network (CDN). When a website’s origin server is unreachable, most CDNs attempt to serve the full webpage from their cache.

But most CDNs don’t enable this feature by default because of the complexity of caching dynamic assets on most websites (e.g. WordPress admin dashboard).

An easy way to fix this is to temporarily disable your CDN. For example, if you use the free CDN Enabler WordPress plugin to associate your website assets with the CDN URLs, you can disable the plugin and test your website reloading.

The same goes for using any other plugins you use to connect to your CDN (e.g. WP Rocket, Breeze, W3 Total Cache).

If you cannot access your website admin dashboard, you can disable the plugin via SFTP by renaming the plugin folder name.

CDNs like Cloudflare or Sucuri that provide full proxy services have additional firewalls between their edge servers and your origin server. As a result, HTTP 5xx errors are common when using it. Most of them cache 5xx errors returned from your origin server, making them easy to fix.

Cloudflare’s free plan tends to throw a 5xx error. Unfortunately, since it’s a full proxy service, there’s no quick way to disable it. But before you blame Cloudflare for this, you should know that Cloudflare shows two variants of the 504 Gateway Timeout error.

504 Gateway Timeout on Cloudflare (Variation 1)

Cloudflare will show you a custom 504 gateway timeout error screen if your site’s origin server responds with a standard HTTP 504 response.

Here the problem is with your web server and not with Cloudflare. You can try to fix the problem with the other solutions mentioned below or contact your hosting provider’s support for technical help.

504 Gateway Timeout at Cloudflare (Variant 2)

When Cloudflare causes the 504 Gateway Timeout error, the error screen will mention “cloudflare”, which is currently the default server name for all Cloudflare assets. Usually the error screen is shown as follows:

Because Cloudflare itself isn’t responding, you won’t see a Cloudflare-branded error screen here.

Most likely, Cloudflare is already aware of the issue and is already working on a fix. You can confirm this by checking the Cloudflare System Status webpage. Alternatively, you can contact Cloudflare Support for a faster resolution.

504 Gateway timed out on Cloudflare due to large uploads

The size of your uploads to your website can also be a reason for server timeouts. Cloudflare limits upload file size (per HTTP POST request) to just 100MB on both Free and Pro plans.

The problem may be on your host’s side or with Cloudflare. You can find out the exact cause by bypassing Cloudflare with your DNS hosts file and trying the upload again.

If you’re using Cloudflare with WordPress, I recommend using the free plugin and excluding critical URLs from caching (e.g. the WordPress admin dashboard). You can refer to Kinsta’s detailed post on configuring Cloudflare settings for WordPress.

Suggested reading: How to Set Up Cloudflare APO for WordPress.

Server issues (check with your host)

Server issues are one of the most common reasons for a 504 gateway timeout error. Since most WordPress sites are hosted on Nginx or Apache web servers, Nginx or Apache is waiting for a response from something and times out.

Many clients come to Kinsta because of this very issue they face with other WordPress hosts. The conversation goes something like this:

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We have around 100,000 visitors per month with more than 200,000 views. Currently we’re hosting with ____ and we’re constantly experiencing 504 errors due to server overload. I don’t like how ____ has handled the issue and we have also been told that we will have to move to their dedicated plans soon which I don’t think is necessary.

High-traffic and e-commerce sites are more prone to 504 errors due to server congestion as they generate many uncacheable requests. However, this problem can occur with any website, including simple blogs. Many hosts will ask you to upgrade to a high-tier plan to fix the problem, which in most cases is unnecessary.

Kinsta uses LXD managed hosts and orchestrated LXC software containers for each site. Thus, each WordPress site resides in its own isolated container with access to all the software needed to run it (Linux, Nginx, PHP, MySQL). The resources are 100% private and are not shared with other websites, not even your websites.

Most WordPress hosts that offer shared hosting plans do not have this feature. Therefore, a high-traffic website hosted on the same server as yours can cause your website to throw a 504 error as well.

Aside from isolating each site in its container, Kinsta also designed its infrastructure to easily handle thousands of simultaneous connections. Kinsta even hosts the MySQL databases on localhost, not a remote server. This means no latency between machines, resulting in faster queries and fewer chances of timeouts.

Many clients migrating to Kinsta see a huge decrease in overall load times.

An overloaded server is not the only cause of a server timeout. There can be many other reasons for the 504 error:

Slow server infrastructure

The server you are using to host your WordPress site may not have enough resources to handle the load. It’s like playing a modern, graphics-intensive video game on a decades-old PC.

The server simply hangs up trying to serve the website. The only solution to this problem is to upgrade to a server with better infrastructure. Because of this, even Kinsta’s most basic WordPress hosting plan will handle a medium-traffic static site.

Requires more PHP workers

PHP workers are used to run your WordPress site’s code. An e-commerce website with 50,000 visitors per month requires a lot more resources than a simple blog with the same amount of traffic. When all of the server’s PHP workers are busy, they build up a queue.

If the queue gets too big, the server ignores old requests, which can cause the server to throw a 504 gateway error. You can ask your host if you can increase the number of your PHP workers. This allows your website to run multiple requests at the same time.

firewall issues

Your server’s firewall might have some bugs or misconfiguration. Perhaps some of its rules are preventing the server from connecting properly. To determine if your firewall is the culprit, you can check your server’s error logs.

Network connection problems

Connection problems between the proxy server and the web server can cause delays in responding to HTTP requests. If you are using a load balancer, you may also experience network connectivity issues.

HTTP timeouts

HTTP timeouts can occur when a connection between the web server and the client is kept open for too long. For WordPress sites, this usually happens when running WordPress imports. One way to solve this problem is to switch to a faster internet connection.

You can also use a tool with WP-CLI support to run the scripts directly on the server and bypass the HTTP connection entirely. For example, you can use the WP-CLI wp import command to run the WordPress importer plugin directly from the command line interface.

Important: 504 Gateway Timeout errors look similar to 503 Service Unavailable errors or 502 Bad Gateway errors. But they are all different. If Kinsta encounters a 504 error, open a support ticket to get your issue fixed immediately.

To monitor your website downtime yourself, you can use a tool like updown.io. It regularly checks the status of your website (or any URL) by sending an HTTP request to it. You can set the check frequency from 15 seconds to 1 hour. If your website does not respond properly, you will be notified by email or SMS.

You get a generous amount of free credits with every updown.io account, but if you’re looking for cheaper alternatives, you can check out WebGazer or UptimeRobot. These two tools allow you to monitor your website’s uptime every 5 minutes for free. That’s decent enough for most website owners.

Monitoring your website will give you an idea of ​​how often it has gone down. This is especially helpful if you use a shared hosting provider. Most managed WordPress hosts will do this for you automatically. So it is always recommended to go with them.

For a detailed explanation, see Kinsta’s post on the importance of managed WordPress hosting.

Spam, bots or DDoS attacks

Malicious attackers can cripple your web server by sending too many and/or resource-intensive requests. If your website is spammed by bots or subjected to a DDoS attack, it can overload your server and cause 504 gateway timeout errors for many real users.

You can look at your server traffic and analytics to see if you can spot erratic patterns in site traffic. If you use Kinsta to host your site, you can easily view this data by going to your MyKinsta Analytics dashboard.

Start your investigation by looking at the top client IPs. It gives you an idea of ​​who is generating the maximum number of requests and from where. If your server suddenly consumes a huge amount of bandwidth or attracts a lot of traffic, this report will come in very handy.

Next you can look at the cache analysis report. Here you can see how many requests bypass or miss the cache or are served from the cache. For performance and stability reasons, you’ll want to cache as many requests as possible, but that’s not always possible.

For example, WooCommerce sites generate a lot of non-cacheable requests for features like the shopping cart and checkout.

Struggling with downtime and WordPress issues? Kinsta is the hosting solution built for performance and security! Check out our plans

Finally, you can use a WordPress security plugin to improve your site’s security by detecting and blocking worrisome traffic/IPs. You can also ask your host to block specific IPs.

Depending on the length and scale of the attack, this could be an endless process of IP blacklisting, as many attackers change their IPs and proxy addresses after being blocked.

Note: Kinsta does not allow its clients to install WordPress security plugins as they can have a major impact on the site’s performance, especially its scanning abilities. Since Kinsta uses load balancers with Google Cloud Platform, blocking IPs would not always work as intended.

You can use dedicated security solutions like Cloudflare or Sucuri to protect your websites from DDoS attacks and spambots. For more information, see Kinsta’s articles on installing Cloudflare on your WordPress site and how Sucuri helped stop a DDoS attack.

Corrupt WordPress database

Sometimes a 504 gateway timeout error can be due to a corrupted database, especially on WordPress sites. Typically this is due to corrupted database tables or files. Sometimes this can also be caused by a serious security issue, e.g. B. if your website or database is hacked.

Repairing a corrupt WordPress database depends on the problem. Plugins like WP-DBManager make it easy to diagnose and repair database problems. I recommend reading Kinsta’s detailed guide to repairing WordPress database issues to get started.

Check your website’s plugins and themes

In most cases, third-party plugins and themes do not cause 504 errors. But there is a small chance that they cause server timeouts, usually by queuing a lot of uncached requests generated by the plugin/theme. Since this ties up many of your server’s PHP workers, you may get 504 errors.

A good example of this problem is WooCommerce, a plugin that is installed to add ecommerce functionality to WordPress sites.

The easiest way to fix this problem is to disable all your plugins. Remember that you won’t lose any data by deactivating just one plugin.

If you can access your admin dashboard, you can go to the Plugins screen, select Disable from the Bulk Actions menu, highlight all plugins, and then click the Apply button. This will disable all your plugins.

If you are unable to access your admin panel, you can disable plugins via SFTP using the method previously outlined. Simply rename the main plugins folder name to disable all plugins in bulk.

After disabling all plugins, check if your website loads properly. If it works you need to activate each plugin and test the site after activating each plugin.

Finally, make sure your plugins, themes, and WordPress core are up to date. Also, make sure your server is running the recommended version of PHP.

If you feel this is too overwhelming, you can always contact your host for help. Kinsta uses Kinsta APM and other troubleshooting techniques to help customers narrow down which plugin, query, or script might be causing the error.

In the worst case, like an inefficient query or broken code in a plugin/theme, you can bring in a WordPress developer to fix the problem.

Check the error logs

Viewing error logs can be very helpful in fixing and debugging 504 errors on your WordPress site. This can help you quickly isolate an issue on your site, especially if it is due to a demanding plugin on your site.

If you’re a Kinsta client, you can easily see errors in the log viewer in your MyKinsta dashboard.

If your host doesn’t have a logging tool, you can enable WordPress debug mode by adding the following code to your wp-config.php file:

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

The WP_DEBUG constant enables or disables the WordPress debug mode. It has two optional companion constants that can extend its capabilities. The constant WP_DEBUG_LOG instructs all errors to be saved in a debug.log file in the /wp-content/ directory. If you don’t see this file, you can always create one.

The constant WP_DEBUG_DISPLAY controls whether debug logs are displayed on the HTML page. Setting this to false will hide all errors, but you can check the errors later since you also defined WP_DEBUG_LOG as true.

Important: If you have WP_DEBUG enabled in the Kinsta environment, it will forward all errors to the debug.log file and not error.log in the MyKinsta dashboard.

You can also download the raw WordPress error log files via SFTP. You can usually find error logs in the root of your server in a folder called “logs”.

Kinsta users can also enable WordPress debug mode from their MyKinsta dashboard. To do this, navigate to Sites > Tools > WordPress Debugging and click the Enable button. This allows you to see PHP errors and notices without enabling debug mode via SSH or SFTP.

Finally, you can check the server log files. Depending on which server you use to host your WordPress site, they can often be found in these locations:

Apache: /var/log/apache2/error.log/

Nginx: /var/log/nginx/error.log/

For more information, see Apache or Nginx logging-related documentation.

Configure Apache or Nginx settings properly

You can edit your server configuration files to increase the resource limits for specific directives. This can help you to fix 504 gateway timeout error.

For Apache web server

First add the following code to your httpd.conf:

time out 600

This setting defines how long the server waits for certain requests before marking them as a network timeout problem. The default value is 60 seconds (Apache 2.4 version).

You can only put this directive in your httpd.conf file, not in your .htaccess file. Since most shared hosting providers don’t allow you to modify the httpd.conf file, you can try increasing the value of the LimitRequestBody directive in your .htaccess file instead.

Then add the following line to your php.ini file:

max_execution_time 300

The default value of the PHP directive max_execution_time is 30 seconds. Increasing it allows your website’s PHP scripts to run longer.

For Nginx web server

If you run your WordPress sites on Nginx + FastCGI Process Manager (PHP-FPM) or use Nginx as a reverse proxy for Apache, you can tweak server settings to avoid 504 gateway timeout errors.

504 gateway timeout error on Nginx + FastCGI (PHP-FPM)

First you need to edit your PHP-FPM pool configuration file. You can find it in the location /etc/php7.4/fpm/pool.d/www.conf on your Nginx server (the exact path may vary depending on the PHP version). Alternatively, you can run the following command in your terminal to edit the PHP-FPM pool configuration file:

sudo nano /etc/php/7.2/fpm/pool.d/www.conf

Next, set the following directive:

request_terminate_timeout = 300

After that you need to edit your php.ini file. You can find it under /etc/php.ini . Open the file and add or change the value for the max_execution_time directive to 300 seconds.

max_execution_time = 300

Finally add the following code to the location of your nginx.conf file:

location ~ .php$ { … fastcgi_read_timeout 300; }

Reload Nginx and PHP-FPM for the changes to take effect.

Reload sudo service nginx Reload sudo service php7.4-fpm

The exact PHP-FPM reload code depends on the PHP version installed on your server. Test your site to see if the issue has been resolved.

504 gateway timeout error on Nginx proxy

If you are using Nginx as a reverse proxy server for Apache, you can make it more forgiving of server timeouts by adding the following directives to your nginx.conf file:

proxy_connect_timeout 600; proxy_send_timeout 600; proxy_read_timeout 600; send_timeout 600;

Don’t forget to reload Nginx after making your changes.

Reload nginx sudo service

Other HTTP errors like 504 Gateway Timeout

As mentioned earlier in this article, many other HTTP 5xx errors are similar to the 504 gateway timeout error. That’s because they all happen on the server side. These errors include:

Other HTTP errors caused by client-side issues like 404 Not Found error are also like 504 error. Check out Kinsta’s detailed guide and HTTP status code list for more information.

If you don’t know what caused a 504 gateway timeout error, how can you fix it in time to stop hard-earned visitors from going to competitor’s websites? 🤷‍♂️ All details are in this post. ⬆️

Click to tweet

summary

Your WordPress site can be affected by the 504 gateway timeout error for a number of reasons. In this article, you have learned how to fix them all. Typically, these errors are caused by server-side issues. In this case, you can contact your host and have the problem fixed quickly.

However, you must also understand that this error can be due to plugins, themes, third-party services, inefficient database queries, or a combination of two or more of them. If you are exhausting your server’s resources (e.g. PHP workers), it is recommended to optimize your website for performance.

If you still find that your website is timing out, you may need to update your hosting plan or PHP worker count. I recommend you to consider this option only after exhausting all other solutions discussed in this article.

From simple static websites to complex ecommerce and membership sites, Kinsta’s scalable hosting plans are designed to accommodate all types of websites. To learn more about our scalable cloud hosting, read this article!

Did we miss something? If you are still struggling to fix the 504 gateway timeout error on your WordPress site, leave a comment below.

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.

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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. Clear 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 site 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 tutorial helpful? Yes No

Credit: Hero Images/Hero Images/GettyImages

Error 502 usually indicates a remote problem that has nothing to do with your computer or your internet connection. This is good news as you have nothing to fix, but bad news as the error persists until the people controlling the faulty server figure out they have a problem and fix it. However, depending on the source of the 502 proxy error, you may be able to take steps to fix or bypass it.

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Internet Status Codes

The “HTTP” at the beginning of each URL stands for “Hypertext Transfer Protocol”. HTTP provides your web browser with an orderly way to communicate with web servers – the machine chatter that goes on behind the scenes of your internet experience. As part of HTTP, the server responds whenever your browser interacts with a server, e.g. B. when you try to load a web page with an Internet status code that tells the browser how the interaction went. The most common is Code 200, a generic message that means everything went well. These codes are always there, but your browser doesn’t usually show them to you unless something goes wrong. Code 404 is the most well-known HTTP error code and indicates that the server could not find what your browser was looking for, but proxy error 502 also pops up from time to time.

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video of the day

Code 502: Faulty gateway

The HTTP error code 502 indicates a “bad gateway” or “bad proxy”. When you visit a website, your browser does not necessarily communicate directly with the server hosting the website. There are often intermediary web servers, known as “gateways,” that route web traffic between networks. If something goes wrong between the gateway server and another upstream server – which can be either the target server or another gateway server – the status code that comes back to you is the proxy error 502. It’s not a very informative one Message just telling you that the gateway server received an invalid response. The real problem could be with the upstream server or with the gateway server itself.

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Main sources of 502 errors

If you’re only getting a 502 error for a specific website, it usually indicates a problem with the website’s server. On the other hand, if you are getting 502 errors for all websites, it probably means that your local ISP is having a technical problem. Call them to report the outage; and if you’re using a proxy server for privacy reasons or to circumvent access restrictions, a 502 proxy error could indicate that the proxy server has poor or difficult programming — which isn’t uncommon. In this case, you can try not using the proxy or use a different proxy.

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Steps you can take

If you encounter a 502 error, hold down the “Ctrl” key on your keyboard and press “F5”. This will clear the cache for that page and download a brand new copy. You can also try loading the website in a different browser to make sure it’s not a problem with your browser itself. If these steps don’t work, try restarting your router, modem, and finally your computer. Restarting these devices can fix a variety of errors that lead to Code 502. If you’re tech-savvy, you can temporarily change your DNS server to a free public one. If the problem was with your DNS server, this will bypass the error. Finally, you can try to contact the website with error 502 to report the problem.

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 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 for this error and how to fix it.

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.

Was this troubleshooting playbook helpful? Please let us know by clicking Send Feedback.

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 from 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:

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

The 502 Bad Gateway error is an HTTP status code that means a server on the internet received an invalid response from another server.

502 Bad Gateway errors are completely independent of your particular setup, which means you can see one in any browser, on any operating system, and on any device.

The 502 Bad Gateway error appears in the internet browser window just like web pages.

Microsoft no longer supports Internet Explorer and recommends upgrading to the newer Edge browser. Go to their website to download the latest version.

What does a 502 Bad Gateway error look like?

The 502 Bad Gateway can be customized from any website. Although it’s quite uncommon, different web servers describe this error differently.

Theresa Chiechi / Lifewire

Below are some common ways you can see it:

502 Bad Gateway

502 Service temporarily overloaded

Error 502

Temporary error (502)

502 proxy error

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

HTTP 502

502. This is a mistake

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

HTTP Error 502 – Bad Gateway

Twitter’s famous “fail wheel” error, stating that Twitter is overloaded, is actually a 502 bad gateway error (although a 503 error would make more sense).

A bad gateway error received in Windows Update generates a 0x80244021 error code or the message WU_E_PT_HTTP_STATUS_BAD_GATEWAY.

When Google services like Google Search or Gmail experience a 502 Bad Gateway, the screen often displays a server error or sometimes just 502.

What Causes a 502 Bad Gateway Error?

Bad gateway errors are often caused by problems between online servers over which you have no control. However, sometimes there is no real problem, but your browser thinks there is, thanks to a problem with your browser, a problem with your home networking equipment, or some other reason that you can control.

Microsoft IIS web servers often provide more information about the cause of a specific 502 Bad Gateway error by adding an extra digit after 502, as in HTTP Error 502.3 – The web server received an invalid response while acting as a gateway or proxy , which means Bad Gateway: Forwarder Connection Error (ARR).

An HTTP Error 502.1 – Bad Gateway Error is related to a CGI application timeout issue and should be fixed as a 504 Gateway Timeout issue.

How to Fix a 502 Bad Gateway Error

The 502 Bad Gateway error is often a network error between servers on the Internet, which means the problem isn’t with your computer or your Internet connection.

However, since it’s possible that something is wrong with you, here are some fixes to try:

A HyperText Transfer Protocol (HTTP) 501 Not Implemented server error response code means that the server does not support the functionality required to fulfill the request.

This status can also send a Retry-After header that tells the requestor when to check again to see if the functionality is supported by then.

501 is the appropriate response when the server does not recognize the request method and cannot support it for any resource. The only methods servers must support (and therefore not return 501) are GET and HEAD .

If the server recognizes the method but intentionally does not support it, the corresponding response is 405 Method Not Allowed .

The 502 Bad Gateway error is an HTTP status code that means a server on the internet received an invalid response from another server.

502 Bad Gateway errors are completely independent of your particular setup, which means you can see one in any browser, on any operating system, and on any device.

The 502 Bad Gateway error appears in the internet browser window just like web pages.

Microsoft no longer supports Internet Explorer and recommends upgrading to the newer Edge browser. Go to their website to download the latest version.

What does a 502 Bad Gateway error look like?

The 502 Bad Gateway can be customized from any website. Although it’s quite uncommon, different web servers describe this error differently.

Theresa Chiechi / Lifewire

Below are some common ways you can see it:

502 Bad Gateway

502 Service temporarily overloaded

Error 502

Temporary error (502)

502 proxy error

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

HTTP 502

502. This is a mistake

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

HTTP Error 502 – Bad Gateway

Twitter’s famous “fail wheel” error, stating that Twitter is overloaded, is actually a 502 bad gateway error (although a 503 error would make more sense).

A bad gateway error received in Windows Update generates a 0x80244021 error code or the message WU_E_PT_HTTP_STATUS_BAD_GATEWAY.

When Google services like Google Search or Gmail experience a 502 Bad Gateway, the screen often displays a server error or sometimes just 502.

What Causes a 502 Bad Gateway Error?

Bad gateway errors are often caused by problems between online servers over which you have no control. However, sometimes there is no real problem, but your browser thinks there is, thanks to a problem with your browser, a problem with your home networking equipment, or some other reason that you can control.

Microsoft IIS web servers often provide more information about the cause of a specific 502 Bad Gateway error by adding an extra digit after 502, as in HTTP Error 502.3 – The web server received an invalid response while acting as a gateway or proxy , which means Bad Gateway: Forwarder Connection Error (ARR).

An HTTP Error 502.1 – Bad Gateway Error is related to a CGI application timeout issue and should be fixed as a 504 Gateway Timeout issue.

How to Fix a 502 Bad Gateway Error

The 502 Bad Gateway error is often a network error between servers on the Internet, which means the problem isn’t with your computer or your Internet connection.

However, since it’s possible that something is wrong with you, here are some fixes to try:

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.

A HyperText Transfer Protocol (HTTP) 501 Not Implemented server error response code means that the server does not support the functionality required to fulfill the request.

This status can also send a Retry-After header that tells the requestor when to check again to see if the functionality is supported by then.

501 is the appropriate response when the server does not recognize the request method and cannot support it for any resource. The only methods servers must support (and therefore not return 501) are GET and HEAD .

If the server recognizes the method but intentionally does not support it, the corresponding response is 405 Method Not Allowed .

You look at the Apigee Edge documentation.

Check out the Apigee X documentation.

Was this troubleshooting playbook helpful? Please let us know by clicking Send Feedback.

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 from 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: