NGINX is not showing PHP 500 error log (nor does php-fpm)

Problem

I received a 500-error on my API request to a PHP backend. The result was returned as a 500 html status.

When searching the logs, there was no mention of this 500 error, other than in the access log of nginx.

Where does nginx or php-fpm put the backtrace of PHP errors?

Solution

Turns out, you need to enable catch_workers_output = yes in your www.conf file, typically located over at /etc/php/7.4/fpm/pool.d/

# file /etc/php/7.4/fpm/pool.d/www.conf
...
catch_workers_output = yes
...

The comments above that line explains it pretty well:

; Redirect worker stdout and stderr into main error log. If not set,
; stdout and stderr will be redirected to /dev/null according to
; FastCGI specs.
; Note: on highloaded environement, this can cause some delay in
; the page process time (several ms).
; Default Value: no

Set up NGINX as a proxy for your Docker containers

Recently I’m a fan of serving docker containers over serving Virtual Hosts using a webserver.

In order to use regular domainnames without ports, I set up Nginx to receive the request on the domainname and let it forward the request to the relevant Docker container on the specific port it is running on.

Example

Imagine I have a Docker webserver-container hosting my app. It runs on my server exposing port 8080. I use the URL app.pauledenburg.com.

I don’t want people to use http://app.pauledenburg.com:8080 but just the URL without the port

http://app.pauledenburg.com

 .

I use nginx for this:

server {
    listen 80;
    server_name app.pauledenburg.com;

    location / {
        proxy_pass http://localhost:8080;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

And now add SSL to it 🙂