How to get php-fpm to log to stdout / stderr when running in a docker container

english
#1

I have php-fpm in a docker container and in the Dockerfile I edit the fpm config file (/etc/php5/fpm/pool.d/www.conf) to set up access logs to go to /var/log/fpm-access.log and error logs to go to /var/log/fpm-php.www.log:

# Do some php-fpm config
#  Redirect worker stdout and stderr into main error log
#  Activate the fpm access log
#  Enable display errors
#  Enable the error log
RUN sed -i '/^;catch_workers_output/ccatch_workers_output = yes' /etc/php5/fpm/pool.d/www.conf && \
    sed -i '/^;access.log/caccess.log = /var/log/fpm-access.log' /etc/php5/fpm/pool.d/www.conf && \
    sed -i '/^;php_flag\[display_errors\]/cphp_flag[display_errors] = off' /etc/php5/fpm/pool.d/www.conf && \
    sed -i '/^;php_admin_value\[error_log\]/cphp_admin_value[error_log] = /var/log/fpm-php.www.log' /etc/php5/fpm/pool.d/www.conf && \
    sed -i '/^;php_admin_flag\[log_errors\]/cphp_admin_flag[log_errors] = on' /etc/php5/fpm/pool.d/www.conf

This works fine - I can get a shell into the container to see the logs. But... it is not best-practice.

The problem is when I try to use the docker log collector - I need php-fpm to log to stdout or stderr so docker can capture them and provide them to the docker logs command.

I tried to do this in the Dockerfile (which is a idea I copied from the official nginx docker image):

# Redirect fpm logs to stdout and stderr so they are forwarded to the docker log collector
RUN ln -sf /dev/stdout /var/log/fpm-access.log && \
    ln -sf /dev/stderr /var/log/fpm-php.www.log

This is not working - no access logs are seen from docker logs - I'm trying to figure out why? Did anyone else that uses fpm in docker manage to get logging working to the docker log collector?

#2

Ok, the way to do this is to send the error and the access logs to the following address:

/proc/self/fd/2

In php5-fpm.log add:

access.log = /proc/self/fd/2
error_log = /proc/self/fd/2

NOTE: access.log is correct, find in this page https://www.php.net/manual/en/install.fpm.configuration.php

#3

Note that the baked in fpm config for the latest version of the official PHP fpm docker image writes to the standard streams:

error_log = /proc/self/fd/2

...

; if we send this to /proc/self/fd/1, it never appears
access.log = /proc/self/fd/2
#4

PHP-FPM logs will only appear in STDERR - so you can symlink the fpm.log to /dev/stderr if you want.

ln -sf /dev/stderr /var/log/fpm-access.log
ln -sf /dev/stderr /var/log/fpm-error.log