Скачать или смотреть Resolving 502 Bad Gateway Error with Docker NGINX Reverse Proxy for Gitea on VM

This guide provides a clear and comprehensive guide to troubleshoot and fix the `502 Bad Gateway` error encountered when setting up a Gitea instance on a VM using Docker and NGINX.
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This video is based on the question https://stackoverflow.com/q/62537209/ asked by the user 'Martin Müsli' ( https://stackoverflow.com/u/10099689/ ) and on the answer https://stackoverflow.com/a/62538313/ provided by the user 'bellackn' ( https://stackoverflow.com/u/6482759/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting 502 Bad Gateway Error in Docker NGINX Setup

Setting up a web application can sometimes lead to unexpected hurdles, especially when using technologies like Docker and NGINX. One common issue many users encounter is the dreaded 502 Bad Gateway error. In this post, we’ll dive into one specific case where this error occurs while trying to set up a Gitea instance on a Virtual Machine (VM) using Docker Compose.

The Problem

You have configured a Gitea web application within a Docker container and set up NGINX as a reverse proxy. However, when you try to access your application via browser at 192.168.33.10:80, you’re met with a 502 Bad Gateway message. This issue can be perplexing and requires some digging into logs and configurations to find a solution.

A Quick Look at the Logs

When you check your NGINX logs with the command docker logs production_nginx, you receive the following error message:

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This message indicates that NGINX is unable to connect to the upstream service (Gitea) running at the specified IP address and port.

Why This Happens

The root cause can often be traced back to permissions and port binding issues. In the case of the Gitea Docker container, it seems that the server is trying to bind to port 80, which is typically restricted to privileged users. This leads to the error message in the logs indicating a failure to start on that port due to a permission denied issue.

The Solution

To resolve this issue, you’ll need to change the port configuration for Gitea to avoid this permission problem. Here’s how you can do it:

Step 1: Modify Your docker-compose.yml

In your docker-compose.yml, update the environment variable for the Gitea server’s HTTP_PORT from 80 to 3000:

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Step 2: Adjust the NGINX Configuration

Since you've changed Gitea's HTTP port, you also need to make sure your NGINX configuration points to the right upstream server:

Update the nginx.conf File

Make sure your upstream definition reflects the port change. Here’s how your nginx.conf might look after the modification:

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Final Steps

Redeploy Your Docker Containers: After making these changes, you’ll need to stop your currently running Docker containers and redeploy them. You can do this with the following commands:

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Test Your Setup: Access your application again via 192.168.33.10:80 in your browser. If the setup is correct, you should now have access to the Gitea instance without encountering any 502 Bad Gateway errors.

Conclusion

In summary, the 502 Bad Gateway error can often stem from port and permission issues when setting up applications in Docker containers. By modifying the HTTP port for Gitea and ensuring your NGINX configuration aligns with this setting, you can effectively resolve this issue. Troubleshooting these types of errors may require some patience, but with careful examination of logs and configurations, you can ensure a smooth and functional deployment.

If you have any further questions or need assistance, feel free to reach out in the comments below!