While managing a site or merely browsing the internet, encountering the 502 Bad Gateway Error could easily disrupt your workflow. The ‘502 Bad Gateway’ or ‘HTTP Error 502’ is a problem which many users face at some point in time. This problem is more annoying than it seems, as many users don’t know the reason behind this error appearing, particularly when it concerns an urgent online task or business management. Fortunately, as daunting as the problem seems, it can be fixed in an effortless manner if you have the know-how.
In this detailed article, we are going to first define what 502 Bad Gateway error is, then we will discuss why it occurs to any system and finally, we will lay down the steps needed to solve the issue in a methodical manner. This explanation will be beneficial no matter your level or working background, whether you are a web creator, programmer or a naive internet user.
What is the 502 Bad Gateway Error?
The 502 Bad Gateway error takes place when a server, performing the functions of a gateway or a proxy, gets an incorrect response from an upstream server. To break it down simply, whenever you access a website, your browser sends a request to a server and that server does all the processing and returns the data to your browser. If the server processes an error while trying to get information from another server (known as an “upstream server”), a gateway server returns a 502 Bad Gateway error.
This error indication can happen between different server communication steps which ends in the connection being established, hence unable to access the website and an error message resulting. It’s important to note that the 502 error is a server-side issue, meaning that it’s usually not something you can directly fix on the client-side (though there are exceptions).
Common Variations of the 502 Bad Gateway Error
Different platforms and web services can display the 502 Bad Gateway error in forms divergent from one another. Some of the most frequently encountered variations include:
- “502 Bad Gateway”
- “Error 502”
- “HTTP Error 502 – Bad Gateway”
- “502 Proxy Error”
- “502 Service Temporarily Overloaded”
- “502 Server Error”
- “502. That’s an error”
Even though the variations seem distinct at first glance, they describe one fundamental problem: a bad response from the upstream server communicates along a gateway server. The root problem is most likely an internal communication breakdown between the servers and identical steps will need to be taken to resolve the issue.
Which Main Issues Lead to a 502 Bad Gateway Error?
Your server, network, or web browser can all bear problems that lead to the 502 Bad Gateway error. Knowing more about the matters that cause this problem is key to its efficient solving. Focused on the most common causes, below are the main culprits:
1. Server Overload
When a server is unable to handle new requests in a timely manner, it is said to have a server overload. Such situations are very common during traffic spikes like promotional events or product launches when a peak in consumer interest is expected. A server operating under significantly low resources such as bandwidth, RAM, or CPU will oftentimes during high demand situations incorrectly respond to requests. This might overwhelm the user with a 502 Bad Gateway error.
During DDoS attacks, overloaded servers can also occur. This is when multiple systems bombard the server with requests, paralyzing it and causing it to go offline or severely malfunction, which leads to a 502 error.
2. Browser Problems
There are points in time where the 502 Bad Gateway error might occur not because of the server, but rather because of your web browser. Associated with an older browser version or corrupted cache files can add to problems in the communication between your device and the server. In efforts to speed the device’s processes, browsers store cache files to improve efficiency. However, in some cases, due to the nature or age of certain files, problems result during the loading process.
Another browser-related problem could come in the form of a DNS cache that has information that is too old. This could lead to problems in the form of misinterpretation of the domain’s IP address and hence the browser’s DNS. In these scenarios, either clearing the browser’s cache or switching the browser can easily fix the error.
3. Firewall Blocks
A firewall is a system that protects a server by cutting the access a malicious server would have to a specific network. Sometimes, firewalls protect too much and suspend normal processes that appear abnormal, and divert them as suspicious processes. This repeats again and again and fails to establish normal and coherent communication processes between the proxy or gateway server to the upstream server, resulting in the occurrence of a 502 Bad Gateway error.
If you employ a Web Application Firewall (WAF) or any security solution that is cloud-based such as Cloudflare, chances are that such services could block access from otherwise trusted entities or normal requests that are deemed on the face suspicious at best.
4. Issues Relating to Domain Name System (DNS)
Every domain name has some numerical identity known as an IP address that servers utilise whenever they communicate. The Domain Name System (DNS) is in charge of translating the domain name to its corresponding IP address. Problems with DNS settings, such as obsolete DNS records or a corrupted DNS cache, could lead to the failure in resolving the given domain to the correct IP address and could lead to a 502 Bad Gateway error.
As an example, if the DNS records for your domain are incorrect and are directing you to the wrong server, then the elementary proxy server won’t access the correct resources and receive the needed files leading to the error. This can easily be solved by flushing the DNS cache.
5. Faulty Web Programming
The more complex and responsive the code that a site uses, the more likely it is to have programming issues that prevent the server from replying to requests on time and more likely it will have to face 502 errors. Such situations frequently arise because of custom code, scripts, or applications that are written specially for a particular website.
The error code 502 can stem from a variety of programming mistakes:
- There are bugs in the PHP Scripts
- There are poorly optimised queries/functions causing overloads in memory
- There are inefficient timeouts
In the case where custom scripts or CMS plugins are used on your website, check for any recent edits along with the updates that could be triggering the problem.
6. Plugins or Themes (For CMS Users)
If you are a student blogger or use WordPress, Joomla, or even Drupal, lack of proper maintenance as well as mismanagement of certain settings (buggy themes) may lead you to incur a 502 Bad Gateway error. Themes and plugins serve to enable a greater level of customisability on your website, but if mismanaged, they cause the server and gateway to become unresponsive to one another.
Consider a scenario where a plugin goes berserk bringing about endless resources clogging storms along with impossible timeouts. Plugins like this lead to resource overflow errors. Furthermore, server misconfigurations caused by outdated plugins can lead to server meltdown due to incompatibilities which fail to bridge vital server dependencies.
7. Content Delivery Network (CDN) Issues
A Content Delivery Network (CDN) caches static resources such as images, videos, and scripts on multiple servers around the world. CDNs aim to optimise website loading times and enhance performance by serving cached content from the most proximate server.
However, CDN misconfiguration or CDN failure may cause issues in attempting to fetch data from the origin server, yielding a 502 Bad Gateway error. Some common issues are incorrect DNS settings or temporary outages within the CDN network.
Steps To Resolve the 502 Bad Gateway Error
With the causes of the 502 Bad Gateway error in mind, it’s time to take a look at the step-by-step instructions you can follow to troubleshoot and resolve the problem. This guide contains both basic and advanced troubleshooting steps to help you identify and resolve the error.
1. Refresh the Webpage
Sometimes, the simplest approach is the best. The very first step in resolving the issue of 502 Bad Gateway is reloading the webpage. If the problem is temporary or the server is overloaded, refreshing the page might resolve it.
To refresh this particular page:
- Locate and press the F5 key or the Ctrl + F5 buttons on your Windows device.
- For Mac users, they can press the Cmd + R buttons.
Doing this will make the browser update the page from the very beginning and disregard all errors made in the last session. Usually, it resolves issues caused by temporary network problems or server congestion.
2. Verify the Site Status
If the first option does not work, the next step is checking whether the site is down for all users or only accessible by you on an individual basis. If only one server is facing some technical difficulties, then it’s likely that’s the reason you are encountering the 502 error.
Websites such as Down for Everyone or Just Me or Is It Down Right Now? can be used to confirm whether the site has gone offline for everyone or if it is only offline for a specific device or network. If it is confirmed that the website is offline for everyone, then the server is most likely at fault. In this scenario, users will simply need to wait until the server administrators resolve the problem.
3. Change Your Browser
Another potential cause of the 502 Bad Gateway error could be your web browser. Sometimes, browsers have outdated data or problematic cached files which can impede access to websites. As a first step, rule out potential browser-based errors by trying a different internet browser to access the website.
Should the issue resolve itself with the new internet browser, you know the source is your original browser. You should then do the following:
- Clear the browsing history along with cache and cookies in your original browser.
- Update the browser to the latest version.
- Temporarily disable any add-ons and extensions that might be preventing the pages from loading.
If the error is browser-specific, setting the browser to update, or reinstalling, should resolve the issue.
4. Clear Your Browser Cache
Another primary reason for the 502 Bad Gateway Error is corrupted or outdated browser cache. In order to load pages, browsers save certain files in their cache. These files can become problematic if they become outdated thus creating conflicts with the server.
To clear your browser’s cache:
- Google Chrome: Settings > Privacy and Security > Clear Browsing Data > Select Time and Data Types to Clear.
- Mozilla Firefox: Settings > Privacy & Security > Cookies and Site Data > Clear Data.
- Safari: Safari > Preferences > Privacy > Manage Website Data > Remove All.
- Microsoft Edge: Settings > Privacy, Search, and Services > Clear Browsing Data.
By clearing the cache, all previously stored files dynamically get replaced with new fresh ones. In some situations, these previously stored files hinder optimal performance. Problems in your browser could potentially be solved through this method. If the problem did persist, try refreshing the page after waiting some time.
5. Try Another Device or Network
The problem can sometimes be related solely to your specific device or network settings. To see if the problem is a result of your device or network, try to access the website with another device (smartphone, tablet, or any desktop) or different network (like by switching from Wi-Fi to mobile data or vice versa).
If the problem is not present on other devices, then the issue may rest on your device and setup. This may include your device’s settings, the local area network (LAN), and in some extreme cases, your Internet Service Provider (ISP) may be the issue.
6. Check DNS Settings
Inadequate Domain Name Server (DNS) settings could very well be the explanation for the 502 Bad Gateway Error problem. Any domain name that has to be translated to its respective IP address is done by the DNS. Mishandling any of the sets within the DNS could result in server communication failure.
Clearing a computer’s stored DNS info is called flushing the DNS cache. If this is the step you wish to take, follow these instructions:
- For Windows Users:
- The command prompt can be accessed by pressing the ‘Win’ button along with the letter ‘R’. Type cmd and press enter.
- Type ipconfig /flushdns and press Enter.
- Further clearing the cache would provide the local machine fresh DNS records instead of stale ones.
- For macOS users:
- Head to Applications, find Utilities, and click on Terminal.
- Type dscacheutil -flushcache and press Enter.
- This too aims to resolve OS identified issues by clearing them.
After deleting the cache with either command, submit the command ‘refresh’ on the browser and see if the problem persists or not.
7. Temporarily Turn Off the CDN or Firewall
If you have a firewall set up, or even if you are using a Content Delivery Network (CDN) like Cloudflare, they could be the ones causing the problem. This is likely the case if you are seeing the 502 Bad Gateway error message. CDNs are used to cache content to improve web service efficiency, but in the case that the CDN does not communicate well with the originating server, a 502 Bad Gateway error may occur.
Similarly, firewalls can block malicious traffic intending to harm your network, but they can also block good traffic mistakenly. In order to figure out if these services are indeed causing the problem, try accessing the website after disabling them. Here is what you need to do:
- Log in to your account on Cloudflare and put the service on hold, temporarily bypassing the service fully.
- Turn off your firewall for a short interval and check if the error still shows up after that.
You may need to adjust the configurations if disabling the CDN or firewall is the issue, or you might have to allowlist them with your server to enhance the communication between your website and the CDN/firewall.
8. Get in Touch with Your Hosting Provider
If you have exhausted all the given options and the problem still persists, it is advisable to get in touch with your hosting provider. Hosting services can access server logs and perform some diagnostic checks that are beyond your reach. The problem could also be in the server itself; the server could be overloaded, have expired scripts, or have misconfigured settings.
When you contact them, make sure you provide them with well-captured details:
- Clearly indicate the error message you are receiving.
- List all the procedures that you have done to try and resolve the issue.
- All other additional important information about the server and website.
Reliable hosts will take no time in solving the issue to help you out, regardless of whether it is the hosting company’s matter or if your settings need adjustments.
9. Disable Plugins and Themes (For CMS Users)
If you are using a content management system (CMS) like WordPress or Joomla, plugins or themes may cause the 502 error. The 502 error may also arise from outdated plugins as they may time out or fail to communicate properly with servers.
To solve this problem, remove all themes and deactivate all plugins and confirm if the error still occurs.
- Log into your WordPress dashboard.
- Click “Plugins > Installed Plugins > Deactivate”.
- As a workaround, attempt to reactivate each individual plugin until you find the one that generates problems.
If you receive an error and cannot access your WordPress site, you are able to disable plugins using FTP or File Manager:
- To disable every plugin, locate the /wp-content/plugins/ folder and change its name e.g., plugins_old.
If the website functions normally now, one or more plugins were the cause of the trouble.
10. Inspect Server Logs
Server logs provide a complete record of all the codes sent and the requests answered from each server. When trying to troubleshoot a 502 error, these logs can be very helpful. These logs are available for most hosting providers through cPanel or other management tools custom to the host.
Logs are generally organised chronologically, so make sure to scan surrounding logs for when the 502 error ostensibly happened. Logs also have clues that indicate time, queues, overloads etc. If these server logs are too complicated for you, consider contacting your hosting provider.
11. Restart PHP Processes
The dynamic content of a website is generated by scripts written in PHP. Many hosting providers give users authority to restart PHP processes directly so 502 errors can be worked around. So, restart the PHP processes and see if the issue resolves.
If cPanel is being utilised, proceed as follows:
- Access cPanel.
- Navigate to the PHP Selector or PHP Configuration section.
- Search for the restart or reset PHP processes option.
Clearing PHP can eliminate some issues that are persisting, including problems with the server and upstream server communicating properly functioning. Reset PHP processes are clear communications bring between the server and upstream server.
12. Perform a Clean Install (Final Option)
At the last stage, when all other approaches do not yield a favourable result, it may be necessitating to erasing the entire website’s content management system (CMS) such as WordPress, known as clean installation. It is associated with removing each file of the website step by step and installing it back file by file in a way that there are no pending repeats. Nevertheless, it is important to state that in order to do that, a copy of the website information, files, and databases must be stored.
Steps include:
- Storing the website files and databases in one collective unit.
- Erase all the files that exist in the server using File Manager or FTP.
- Grab a hold of the most current version of the CMS and conduct the installation.
- Upload the retrieved files and databases.
This technique is one that is the most inefficient and should only be considered if no other attempts have been successful.
Summary
Resolving the 502 Bad Gateway error can be a painful process, and can often strain one’s patience, but knowing what causes it and following the right troubleshooting methods can help remedy the problem. Be it server overload, DNS issues, problems with the browser, or malfunctioning plugins, all issues are catered for in this guide.
By working through each of the 12 outlined steps, one can accurately pinpoint the cause and rectify the problem. It’s important to remember that routine server maintenance, updating software, and clearing cached data can mitigate these concerns. If, after all these efforts, the issue remains unresolved, contacting the hosting provider or a technical expert is recommended.
These troubleshooting tips are intended to allow effortless restoration of the website; while ensuring it functions well for users in the future.