502 Bad Gateway Error

Introduction

When it comes to error in 500 series, there are so many errors that can be very frustrating. Leaving you in a state of confusion on how to figure out the cause of error, ways to fix that error. A few errors that come to our mind are the white screen of death or the frightening database connection not established error. But the most popular error that comes in the category of scary errors is 502 Bad Gateway error. Why? Let's show you.

What is 502 Bad Gateway Error?

502 Bad Gateway error means that one server, while acting as a gateway or proxy, received an invalid response from an inbound server.

An HTTP Status code is a way of server of notifying that something has gone wrong, along with the code on how to diagnose it.

502 Bad Gateway Error Variations

Due to a variety of browsers, web servers, and operating systems, you can see 502 Bad Gateway error in a number of different ways. But they all have the same meaning, only the syntax is different. Below are the different variations you might see on the web:

• 502 Bad Gateway
• Error 502
• HTTP Error 502- Bad Gateway
• 502 Service Temporarily Overloaded
• 502 Proxy Error
• HTTP 502
• 502 That's an error
• 502 bad gateway Cloudflare

There is yet another variation of 502 Bad Gateway error, you might encounter.

What are the Causes and How to Fix 502 Bad Gateway Error?

A 502 error is typically a server problem but in some cases, it can also be a client-side issue.

Here are some fixes that you can try:

1. Try reloading the URL.
2. Start a new browser session by closing all open browser windows and then opening a new one. Try loading the web page again.
3. Clear your browser cache.
4. Delete your browser's cookies.
5. Start your browser in safe mode.
6. Try another browser. If an alternative browser does not produce 502 error, then you need to reinstall your browser.
7. Restart your computer.
8. Restart your Networking Equipment.
9. Change your DNS servers.
10. Contact your website provider.
11. Contact your Internet Service Provider.
12. At this point in your troubleshooting, the 502 Bad Gateway error message is an issue with either your ISP or with the website's network. So you'll need to wait until the problem is solved for you.

Fixes of 502 Error for different platforms

So, we will dive into more details and will see the Causes and ways to Fix 502 error in various platforms.

1. Webhook
2. PHP Script
3. Nginx
4. Wordpress
5. Magento Installation
6. Plesk

Webhook

Webhook comes in handy when we want to connect with different applications. Web are basically calls from one server to another. There are numerous reasons for 502 error while using Webhook. Let's check the reasons in detail.

S no.	Causes	Fixes
1	Network Error	Replace domain name with IP Address
2	File Permission	Restore from backups or look for recently changed files and fix permissions
3	Firewall settings	Fix firewall rules that block the request
4	Server connectivity	Install mod_evasive, this fixes the server
5	Faulty Programming	Fix simple codes or recommend to app developer regarding probable error

Refer How to Fix 502 error in Webhook for detailed step by step guide to fix error.

PHP Script

502 Bad gateway error occurs when Nginx or Apache is front-end web server & Apache, PHP-FPM or other services is in backend.

When the front-end server is unable to establish a connection to the back-end server, websites hosted by these servers start showing PHP 502 Bad Gateway errors. We have come across a number of Causes that turn out to be the culprit behind the error.

S no.	Causes	Fixes
1	Server Error	a) When service not running-Use website logs or an application to fix server errors b) When service running- if there is a timeout error, increase execution time, buffer size and timeout settings of service
2	Configuration Issues	Correctness of settings of path, port, user and group etc. are checked.
3	Mod-security restrictions	mod-security configuration, APC cache are reviewed and issues are sorted.
4	Cloudflare settings	Cloudflare settings are reviewed and fix the discovered issues
5	Port or permission issues	Check port connectivity, firewall rule or related socket file. Proper access rights and permissions are granted.
6	Software bugs	Problematic web code or a query needs to be fixed
7	High server load	Tweak process count to an ideal value that will be easily supported by server resources.

Refer How to Fix 502 error in PHP Script for detailed step by step guide to fix error.

Nginx

Maintaining server is a task, where you have to deal with all the upgrades, security patches and the occasional server errors. We've listed reasons for 502 Bad Gateway error and how to fix them.

S no.	Causes	Fixes
1	Backend service failed	Try killing all unresponsive processes and restarting the service.
2	High Server load	Identify which resource is being abused, which service is abusing that resource, which user owns the abusive software.
3	Incorrect service configuration	Scan error log to see what error says, then make changes accordingly
4	Service port blocked in firewall	If any service is running on non-standard ports, either change the service configuration to change to standard port or change firewall configuration to allow non-standard port
5	Web Application bugs	Reconfigure the services to match the required versions

Refer How to Fix 502 error in Nginx for detailed step by step guide to fix error.

Wordpress

When it comes to Wordpress, there can be a lot of errors that can be very confusing. 502 Bad Gateway is one such error. Checkout Causes and fixes of 502 error in Wordpress.

S no.	Causes	Fixes
1	Server Overload	Try reloading the page or clear your browser cache
2	DNS Issue	a) Try flushing DNS Cache b) Temporarily change DNS Server
3	Host Issue	Try switching to Host that runs site in isolate software containers
4	CDN or Firewall Issue	Temporarily disable CDN or Firewall
5	Bad Plugin	Try disabling the Plugin
6	Bad Theme	Ensure themes are up-to-date and try switching to the basic version in case of error due to theme
7	PHP error	Try restarting PHP or contact host provider to restart PHP for you
8	PHP timeout error	Tweak timeout values after analyzing the values already set on the server

Refer How to Fix 502 error in Wordpress for detailed step by step guide to fix error.

Magento Installation

A major share of 502 Bad Gateway error in Magento happens due to PHP issues. Magento is one of the best eCommerce platforms in the market. Checkout top Causes and Fixes for 502 error in Magento.

S no.	Causes	Fixes
1	Exceeding PHP Limits	Inspect and disable the module linked to top memory consuming process.In cases of memory constraints, upgrade memory on server.
2	Nginx Configuration limits	Fix involves determining correct buffer sizes and increase the size if required.

Refer How to Fix 502 error in Magento for detailed step by step guide to fix error.

Plesk

From Plesk version 12 onwards, Nginx is supported as a reverse proxy. Plesk Bad Gateway error occurs when the proxy server received an invalid response or no response from the upstream server.

To fix an error, we have identified the cause of the error and provided a recommended solution for each cause.

S no.	Causes	Fixes
1	Service errors	Identify and fix the reason for service downtime and restart the service.
2	Configuration issues	In case of timeout errors, fine-tune parameters like execution time, buffer sizes, timeout settings etc.
3	Port blocks	Identify the correct ports on which Plesk service runs and edit firewall configuration to allow connections to these ports
4	Fail2ban Firewall	Either upgrade Plesk or if upgrade is not possible manually add the server IP Address to Fail2ban list if trusted IP Address.
5	Version Conflicts	Analyze software requirements and re-configure the services to match the required version

Refer How to Fix 502 error in Plesk for detailed step by step guide to fix error.