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Dockerized Jobber Cron

Docker Container Cron Alternative With Jobber.

Supported tags and respective Dockerfile links

Bundle Version Tags Dockerfile Readme Example
Jobber latest, v1.2 latest, v1.2 Dockerfile Readme blacklabelops/jobber:latest
Jobber + Tools latest, v1.2 tools, tools.v1.2 Dockerfile blacklabelops/jobber:tools
Jobber + Docker Tools latest docker, docker.v1.2 Dockerfile Readme blacklabelops/jobber:docker
Jobber + AWS Cli latest, v1.2 aws, tools.v1.2 Dockerfile Readme blacklabelops/jobber:aws
Jobber + GCE Cli latest, v1.2 gce, gce.v1.2 Dockerfile Readme blacklabelops/jobber:gce
Jobber + All Above latest, v1.2 cloud, cloud.v1.2 Dockerfile Readme blacklabelops/jobber:cloud

AWS = Amazon Web Services, GCE = Google Cloud Engine

Make It Short!

In short, you can define periodic tasks for an arbitrary number of jobs.

Example:

$ docker run -d \
    --name jobber \
    -e "JOB_NAME1=TestEcho" \
    -e "JOB_COMMAND1=echo hello world" \
    blacklabelops/jobber

Will print "hello world" to console every second.

How It Works

The environment variables are numerated. Just add the number behind the environment variable and the container will create a job definition for Jobber!

This way the container can handle an arbitrary number of jobs without file handling or cumbersome syntax!

Example with two tasks:

$ docker run -d \
    --name jobber \
    -e "JOB_NAME1=TestEcho" \
    -e "JOB_COMMAND1=echo hello world" \
    -e "JOB_NAME2=TestEcho" \
    -e "JOB_COMMAND2=echo hello moon" \
    blacklabelops/jobber

First job will print "hello world" and then second job will print "hello moon" to console every second.

Environment Variables

Globally, there is a notify program defined, default one is sendmail, you can override it using an environment variable, JOBS_NOTIFY_CMD.
This program will receive a JSON payload as specified in the jobber docs

Every job definition is specified by up to four environment variables:

  • JOB_NAME: The identifier for the job, must not contain empty spaces!
  • JOB_COMMAND: The bash command to be executed.
  • JOB_TIME: The cron schedule for the job. See Documentation
  • JOB_ON_ERROR: How Jobber should act on errors. Values: Stop, Backoff, Continue (Default). See Documentation
  • JOB_NOTIFY_ERR: If Jobber should notify on error. Values: true, false. Default is false
  • JOB_NOTIFY_FAIL: If Jobber should notify on failure. Values: true, false. Default is false

Full example:

$ docker run -d \
    --name jobber \
    -e "JOBS_NOTIFY_CMD=/bin/bash" \
    -e "JOB_NAME1=TestEcho" \
    -e "JOB_COMMAND1=echo hello world" \
    -e "JOB_TIME1=1" \
    -e "JOB_ON_ERROR1=Backoff" \
    -e "JOB_NOTIFY_ERR1=true" \
    -e "JOB_NOTIFY_FAIL1=true" \
    blacklabelops/jobber

Will print "hello world" at second 1 of every minute.

The Cron Time

When it comes to the cron string then Jobber is a little bit different. If you do not define any time then the resulting cron table will be

* * * * * *

and the job will be executed every second.

You can also define just one number "1". This will be interpreted as

1 * * * * *

Example:

$ docker run \
    --name jobber \
    -e "JOB_NAME1=TestEcho" \
    -e "JOB_COMMAND1=echo hello world" \
    -e "JOB_TIME1=1 * * * * *"
    blacklabelops/jobber

Will print "hello world" every second.

so you can see that you have to specify the time string from the back and the rest will be filled up by Jobber.

As a reminder, cron timetable is like follows:

  1. Token: Second
  2. Token: Minute
  3. Token: Hour
  4. Token: Day of Month
  5. Token: Month
  6. Token: Day of Week

References