How to run cron jobs inside php-fpm-alpine docker container?

Question

Hi I don't know how can I run a cron job inside this container.

I've found this: How to run a cron job inside a docker container

But that overrides the CMD, I don't know hot to keep php-fpm working

Answer 1

When you need to run multiple processes in your docker container a solution is to use supervisord as the main instruction. Docker will start and monitor supervisord which in turn will start your other processes.

Docker File Example:

FROM debian:9
...
CMD ["/usr/bin/supervisord", "-c", "/etc/supervisor/my.conf"]

Supervisord config example (/etc/supervisor/my.conf):

[supervisord]
nodaemon=true

[program:cron]
command=/usr/sbin/crond -f -l 8
stdout_logfile=/dev/stdout
stderr_logfile=/dev/stderr
stdout_logfile_maxbytes=0
stderr_logfile_maxbytes=0
autorestart=true

[program:php-fpm]
command=docker-php-entrypoint php-fpm

Note that it is desirable to configure supervisord to output the logs to /dev/stdout and /dev/stderr to allow docker to handle these logs. Otherwise you risk your container to slow down over time as the amount of file writes increases.

Answer 2

The main question here is how to make PHP work kind of "in parallel" with the cron. And another answer, besides using supervisor , is to use bash's ability to manage tasks. This is generally mentioned here .
For the Alpine PHP-FPM container and the Cron , the startup script would look like this:

Docker File:

FROM php:8.1-fpm-alpine
RUN apk --update add --no-cache bash
COPY ./crontasks /var/spool/cron/crontabs/root
COPY entrypoint.bash /usr/sbin
RUN chmod a+x /usr/sbin/entrypoint.bash
ENTRYPOINT /usr/sbin/entrypoint.bash

entrypoint.bash file ( the magic is here )

#!/bin/bash
# turn on bash's job control
set -m
# Start the "main" PHP process and put it in the background
php-fpm &
# Start the helper crond process
crond
# now we bring the primary process back into the foreground
fg %1

It is important to keep in mind that the cron job syntax in Alpine is different from Debian. And different folders are used for tasks.