Nginx was launched in 2004 as an open-source web server. Since the time it has been released, it is very commonly used for hosting websites. Apart from this, it is also being used as Load Balancer, Email Proxy, Reverse Proxy, and HTTP Cache. Like every other web server, Nginx is also prone to certain errors, out of which the most common one is the 502 Bad Gateway error. This is a highly generic type of error that arises when you try to access a web server but fail to reach it. In that case, your browser may render the 502 Bad Gateway error. Since there is no other information that appears along with this error, it leaves the user clueless about what exactly went wrong and how they can fix it.
Therefore, in today’s article, we will try to look for all the potential causes of the 502 Bad Gateway error in Nginx, as well as the ways on how we can possibly fix it.
Causes of 502 Bad Gateway Error in Nginx
There could be multiple reasons for a 502 Bad Gateway error in Nginx, and the most common ones are listed below:
Unreachable Domain
Whenever you type in a domain name in the search bar of your browser and press the Enter key to access that website, the very first task that is performed is contacting your Domain Name System (DNS). The DNS server maps the specified domain name onto its reserved IP address and then contacts the respective server, which in turn responds to you by displaying the requested web page on your web browser. However, at times, the DNS server fails to reach the specified domain because of a 502 Bad Gateway error in Nginx. This may happen because of certain changes taking place in your DNS, which takes a sufficient amount of time to take effect after it starts working correctly.
Overly Activated Firewalls
At times, your Firewall settings are so strict and hard that they even block legitimate users and disallow them to reach your site. This, in turn, may cause the users to see a 502 Bad Gateway error whenever they try to access your website.
Hosting Server Goes Down
Since the servers have a finite capacity in which they cannot entertain user requests, therefore, once that capacity is reached, all the future incoming users might experience a 502 Bad Gateway error since your server will be down. Another reason for it could be that you have intentionally brought down your server for maintenance.
Fixing the 502 Bad Gateway Error in Nginx
Depending on the causes of the 502 Bad Gateway error in Nginx, you can try to resolve it by using any of the following solutions:
Refresh your Web Page
At times, you can see a 502 Bad Gateway error only because of some temporary connectivity issues, which can be resolved simply by refreshing your web page and checking if you can access the web page or not. If you still fail to reach the desired web page, then you might also try to clear your browser cache because sometimes, a 502 Bad Gateway error response is saved in your browser cache. Due to this, your browser renders this error again and again, so clearing the cache might resolve this issue.
Perform a Ping Test
If you are still not able to access your web server even after refreshing the web page and clearing the browser cache, then your web server might have some serious connectivity issues. In that case, you can try to perform a Ping Test where you send the Ping request to your server and check if it is reachable or not. If your server is reachable, then you will be able to access it, if not, then you will have to look for the other solutions that are listed below.
Look for Potential Changes in your DNS
You might have changed your hosting service provider or changed the IP address with whom one can contact your web server. These changes are always reflected in the DNS server, but they take some time to take place correctly. In that case, you need to wait till the changes have taken effect all across your DNS, after which you will no longer be seeing the 502 Bad Gateway error in Nginx.
Monitor your Server Logs
Server logs contain detailed information about the status of your server and all the activities it performs. If you are monitoring the server logs regularly, then they can help you a lot in figuring out exactly what went wrong, hence enables you to fix the 502 Bad Gateway error in Nginx since knowing the exact cause of the error, is in fact, the first step towards resolving that error.
Recheck your Firewall Configurations
You need to apply this fix if you have figured out your Firewall configurations to be too strict that they are even blocking legitimate users to access your website. In that case, resetting your Firewall configurations can easily fix the 502 Bad Gateway error in Nginx.
Debug your Website’s Code
At times, the problem does not trace back to the connectivity issues, rather, it is your website’s code that is faulty, which causes the 502 Bad Gateway error in Nginx. Manually figuring out such errors is nearly impossible, which is why it is highly recommended for you to debug your website’s code in a sandboxed environment. Doing this will not only pinpoint the exact issue that you can immediately fix but will also prevent your physical system from getting harmed by running a faulty code on it since you are running it in a sandboxed environment.
Try Contacting your Hosting Service Provider
Sometimes when you cannot host your own web server, you take the hosting services on rent from a hosting service provider. In that case, the problem that is causing the 502 Bad Gateway error in Nginx, possibly, does not reside in your end, rather, there is some issue with the hosting service that you are getting. The only solution to this problem is contacting your hosting service provider, who will not only take the responsibility of figuring out that issue but might also suggest ways in which you can prevent this error from recurring in the future.
Conclusion
In this article, we provided you a brief introduction of Nginx and the most common type of error that this webserver faces, specifically, the 502 Bad Gateway error. Then, we also stated all the possible causes behind this error. Finally, we shared with you all the different solutions on how you can resolve this error in Nginx.
