Have nginx access_log and error_log log to STDOUT and STDERR of master process

Question

Is there a way to have the master process log to STDOUT STDERR instead of to a file?

It seems that you can only pass a filepath to the access_log directive:

access_log  /var/log/nginx/access.log

And the same goes for error_log:

error_log /var/log/nginx/error.log

I understand that this simply may not be a feature of nginx, I'd be interested in a concise solution that uses tail, for example. It is preferable though that it comes from the master process though because I am running nginx in the foreground.

Answer 1

Edit: it seems nginx now supports error_log stderr; as mentioned in Anon's answer.

You can send the logs to /dev/stdout. In nginx.conf:

daemon off;
error_log /dev/stdout info;

http {
  access_log /dev/stdout;
  ...
}

edit: May need to run ln -sf /proc/self/fd /dev/ if using running certain docker containers, then use /dev/fd/1 or /dev/fd/2

Answer 2

If the question is docker related... the official nginx docker images do this by making softlinks towards stdout/stderr

RUN ln -sf /dev/stdout /var/log/nginx/access.log && ln -sf /dev/stderr /var/log/nginx/error.log

REF: https://microbadger.com/images/nginx

Answer 3

Syntax: error_log file | stderr | syslog:server=address[,parameter=value] | memory:size [debug | info | notice | warn | error | crit | alert | emerg];
Default:    
error_log logs/error.log error;
Context:    main, http, stream, server, location

http://nginx.org/en/docs/ngx_core_module.html#error_log

Don't use: /dev/stderr This will break your setup if you're going to use systemd-nspawn.

Answer 4

For a debug purpose:

/usr/sbin/nginx -g "daemon off;error_log /dev/stdout debug;"

For a classic purpose

/usr/sbin/nginx -g "daemon off;error_log /dev/stdout info;"

Require

Under the server bracket on the config file

access_log /dev/stdout;

Answer 5

When running Nginx in a Docker container, be aware that a volume mounted over the log dir defeats the purpose of creating a softlink between the log files and stdout/stderr in your Dockerfile, as described in @Boeboe 's answer.

In that case you can either create the softlink in your entrypoint (executed after volumes are mounted) or not use a volume at all (e.g. when logs are already collected by a central logging system).

Answer 6

In docker image of PHP-FPM, i've see such approach:

# cat /usr/local/etc/php-fpm.d/docker.conf
[global]
error_log = /proc/self/fd/2

[www]
; if we send this to /proc/self/fd/1, it never appears
access.log = /proc/self/fd/2

Answer 7

Based on the official docker Nginx image this is already in place

For more information you can see the Dockerfile written for the 1-alpine version which soft link the access logs and error logs to the stdout and stderr respectively. Other docker tags also have it.

ref: https://github.com/nginxinc/docker-nginx/blob/1.23.1/stable/alpine/Dockerfile#L118-L119