Overview

The gol af this repository is provides a good way to create microservices running in the schedule time by cron jobs.

how to create a service in docker-compose

A cron job has the following definition:

# Example of job definition:
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# |  |  |  |  |
# *  *  *  *  * user-name command to be executed

keeping it in mind, we have the following pattern in order to create it, we can just to passing these args by enviroment variables as follow:

´´´
environment:
    - USER_NAME=root
    - TASK_SCHEDULE=* * * * *
    - COMMAND=node --version 
´´´

There's a full docker-compose sample here

The entrypoint.sh file is responsable for call setup.crontab.py python script and create the crontab file. After crontab file is created then the cron job service is started by command cron -f

Important Notes

• env >> /etc/environment : the cron jobs not recognize the env variables so this line is very important before call cron -f
• There's a mandatory blank line in the end of crontab file

Running by docker command line

docker build -t <docker-custom-image-name-here> .

docker run -it -e USER_NAME="root" -e TASK_SCHEDULE="* * * * *" -e COMMAND="node --version"  <docker-custom-image-name-here>