Environment variable / tag in docker-compose

In my development environment, I have a docker-compose.yml which builds an image from a Dockerfile.

I then push this to dockerhub, and my PROD servers use that image (using docker-compose-prod.yml). In PROD I'm using docker-swarm (currently three nodes).

When building the image, in the Dockerfile, it uses entrypoint.sh so I can run both apache and cron within the same container.

This is a requirement of the web app I'm working with (whilst I'd ideally split the cron out into a separate container, it's not practical).

The result is that the crontab runs no matter the environment; i.e. whenever I docker-compose up in my DEV environment, the crontab runs. For a variety of reasons, this isn't desired.

I already have different docker-compose.yml files on DEV vs PROD (*-prod.yml), but the task to start crontab is within entrypoint.sh which is embedded within the image.

So, is there anyway I can pass some type of server tag / environment variable within entrypoint.sh so on anything other than PROD, it doesn't start/add the crontab?

For example: new-entrypoint.sh

#!/bin/bash

if NODE IS LIVE
{
  # Setup a cron schedule
  echo "* * * * * /usr/local/bin/php /var/www/html/cron.php >> /var/log/cron.log 2>&1
  # This extra line makes it a valid cron" > /var/www/scheduler.txt

  crontab /var/www/scheduler.txt
  #cron
  service cron start
}

/usr/sbin/apache2ctl -D FOREGROUND

If I was the use an .ENV file and variable, I'm firstly not sure how I'd reference that in the entrypoint.sh but also how do I manage different .ENV files between DEV and PROD (bear in mind I'm running PROD as a docker-swarm).

Or, can I use a node tag (like I can for docker-compose > deploy > placement > constraints)?

Ideally it'll, by default NOT run the crontab, and only run from if a specific ENV or tag is met.

Thanks!

FILES

docker-compose.yml

version: "3.5"
services:
  example:
    build:
      context: .
      dockerfile: ./example.Dockerfile
    image: username/example
...

docker-compose-prod.yml

version: '3.5'
services:
  example:
    image: username/example
...

Dockerfile

FROM php:7.4-apache

RUN ....

# MULTIPLE ENTRYPOINTS to enable cron and apache
ADD entrypoint.sh /entrypoint.sh
 
RUN chmod  x /entrypoint.sh

ENTRYPOINT /entrypoint.sh

entrypoint.sh

#!/bin/bash

# Setup a cron schedule
echo "* * * * * /usr/local/bin/php /var/www/html/cron.php >> /var/log/cron.log 2>&1
# This extra line makes it a valid cron" > /var/www/scheduler.txt

crontab /var/www/scheduler.txt
#cron
service cron start

/usr/sbin/apache2ctl -D FOREGROUND

CodePudding user response：

You can use ENV vars that way:

Set a ENV var in docker-compose-prod.yml

    version: '3.5'
    services:
      example:
        image: username/example
        environment:
          APP_ENV: prd
        ...

And use it in entrypoint.sh


    #!/bin/bash
    if [ "$APP_ENV" == "prd" ]
    then
      # Setup a cron schedule
      echo "* * * * * /usr/local/bin/php /var/www/html/cron.php >> /var/log/cron.log 2>&1
      # This extra line makes it a valid cron" > /var/www/scheduler.txt
      crontab /var/www/scheduler.txt
      #cron
      service cron start
    fi
    /usr/sbin/apache2ctl -D FOREGROUND

In others environments (DEV for example) the var is not set, and the entrypoint.sh doesn't execute code inside if. Hope it helps you.