layeredinsight/dockerjob repository overview

⁠dockerjob

dockerjob arose from a need to be able to easily schedule backup jobs in our VM-image-based software distributions. So we tracked down Crocker⁠ - the cool, light-weight cron-like scheduler desgined for containers, and paired it with Docker's⁠...docker⁠.

The result? The abilty to run a container that runs another container at a specified time, be that for backups, wakeup calls, chaos injection, or whatever other automatable containerism comes to mind...

⁠Usage

To use docker inside the dockerjob container, you'll need to bind-mount your docker socket into the container. From a command line, this is done by providing the parameters -v /var/run/docker.sock:/var/run/docker.sock, presuming your docker socket is in the default location.

dockerjob could be run from the commandline...

docker run --rm -ti -v /var/run/docker.sock:/var/run/docker.sock --entrypoint /usr/local/bin/crocker dockerjob -A "09 10 * * *" docker ps

...but really we wrote this for repeatability and ease-of-use. In a docker-compose.yml file, it could be used like so:

  version: "3.2"
  services:
    mongodb:
      image: mongo:3.2.4
      ports:
        - "27017:27017"
      volumes:
        - type: volume
          source: /data/mongo-data
          target: /data/db
    mongo-backup:
      image: layeredinsight/dockerjob:1.0
      entrypoint: /usr/local/bin/crocker @daily docker run --rm -ti -v /data/mongo-backups:/data/backups mongo:3.2.4 mongodump --gzip -o /data/backups/`date +%Y%m%d` --host=mongodb
      volumes:
        - type: bind
          source: /var/run/docker.sock
          target: /var/run/docker.sock

More details about the arguments to /usr/local/bin/crocker can be found on the crocker github page⁠.

For more details on the format of the cronjob time expression, see the vixiecron manpage(5)⁠.

⁠Troubleshooting

You need to bind mount the docker socket inside the dockerjob container, otherwise you will see the following when trying to run docker commands:

⁠One Final Note...

dockerjob is not what the sample says in Fatboy Slim's Soul Surfing⁠.