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dansocialmind's avatar

One Single Inertia POST request in our application triggers an Nginx 502 Error

I'm losing my mind slightly here, we have a single, simple, POST request in our app that enables something. And it's triggering an NGINX 502 Gateway Error for some reason.

  1. The JSON payload it sends is tiny, three strings, none of which are big, the entire size of the request is around 600B.

  2. We've added logging to the route and it's controller method, the HTTP request never hits the controller method, the 502 is thrown in 600ms - before it ever hits the route's controller method.

  3. It works locally on Laravel Herd just fine, but fails on our production and development/staging environments.

  4. we've already tried increasing the following buffer sizes in Nginx:

client_header_buffer_size 128k;
large_client_header_buffers 4 128k;
fastcgi_buffers 128 128k;
fastcgi_buffer_size 128k;
fastcgi_busy_buffers_size 128k;
proxy_buffer_size   128k;
proxy_buffers   128 128k;
proxy_busy_buffers_size   128k;

  1. The only thing we see in the nginx error log is something that starts with failed (104: Connection reset by peer) while reading response header from upstream

  2. Nothing is logged in php-fpm error log except somtimes we see:

 [pool socialsyncdotdev] child 853468 exited with code 255 after 33.364878 seconds from start

but i'm unsure if this is related or not.

  1. this is the only place in the application where this is happening. It happens if we use Inertia's router.post or if we use axios.post, it doesn't seem to matter.
0 likes
3 replies
LaryAI's avatar
LaryAI
AI
1 year ago
Level 58

A 502 Bad Gateway error in Nginx typically indicates that the server acting as a gateway or proxy received an invalid response from the upstream server. In your case, it seems like the issue is occurring before the request reaches your Laravel application, as indicated by the error message "failed (104: Connection reset by peer) while reading response header from upstream."

Here are some steps you can take to troubleshoot and potentially resolve the issue:

  1. Check PHP-FPM Configuration:

    • Ensure that your PHP-FPM service is running correctly. Sometimes, a misconfiguration or an issue with PHP-FPM can cause 502 errors.
    • Check the php-fpm configuration files (usually located in /etc/php/7.x/fpm/pool.d/ or similar) for any misconfigurations.
    • Increase the pm.max_children setting if your server is under heavy load, as it might be running out of available PHP-FPM workers.

  2. Inspect PHP-FPM Logs:

    • Look for any errors or warnings in the PHP-FPM logs. The error message you mentioned (child 853468 exited with code 255) could indicate a problem with PHP-FPM.
    • Ensure that the PHP-FPM error log level is set to a verbose level to capture more detailed information.

  3. Check Nginx Configuration:

    • Verify that the Nginx configuration is correctly set up to communicate with PHP-FPM. Ensure that the fastcgi_pass directive is pointing to the correct socket or IP address and port.
    • Double-check the buffer settings you have adjusted to ensure they are appropriate for your server's workload.

  4. Review Application Code:

    • Since the issue occurs with a specific POST request, review the code handling this request to ensure there are no infinite loops or resource-intensive operations that could cause PHP-FPM to crash.

  5. Server Resource Limits:

    • Ensure that your server has sufficient resources (CPU, memory) to handle the requests. A lack of resources can cause PHP-FPM to fail, leading to 502 errors.

  6. Network and Firewall:

    • Check for any network issues or firewall rules that might be interfering with the communication between Nginx and PHP-FPM.

  7. Test with Different PHP Versions:

    • If possible, test the application with a different PHP version to rule out any version-specific issues.

If none of these steps resolve the issue, consider enabling more detailed logging for both Nginx and PHP-FPM to gather additional information that might help pinpoint the problem.

Lumethys's avatar

is it the content that cause error or the route itself, what happen if you call the route without any params?

dansocialmind's avatar
dansocialmind
OP
1 year ago
Best Answer
Level 1

Found out what it was, two method calls deep, we were sending another POST request to our logging/metric application inside a defer() call - this was, for some reason, causing the process to terminate.

It wasn't nginx at all, but i had added logging calls into the controller method, and they weren't being logged, so i assumed it wasn't even hitting PHP, i ASSUME this is because the process terminated before Laravel could send the logs.

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