Ian Fijolek
7b2eb917ad
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Rather than trashing the whole schedule, instead compare what is currently scheduled with the newly found containers and then add or remove jobs as needed. Fixes #2 |
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Dockron
Simple scheduling for short-running Docker containers
Usage
Dockron requires access to the Docker, so it may need to be run as root, or, if in a Docker container, need the socket mapped as a volume.
Running Dockron
As simple as:
dockron
It will then run in the foreground, periodically checking Docker for containers with labels containing a cron schedule.
By default, Dockron will periodically poll Docker for new containers or schedule changes every minute. You can specify an interval by using the -watch flag.
Running with Docker
Dockron is also available as a Docker image. The multi-arch repo can be found at IamTheFij/dockron
From either an amd64, arm, or arm64 machine, you can run Dockron using:
docker run -v /var/run/docker.sock:/var/run/docker.sock:ro iamthefij/dockron -watch
Scheduling a container
First, be sure your container is something that is not long running and will actually exit when complete. This is for batch runs and not keeping a service running. Docker should be able to do that on it's own with a restart policy.
Create your container and add a label in the form dockron.schedule="* * * * *", where the value is a valid cron expression (See the section Cron Expression Formatting).
Dockron will now start that container peridically on the schedule.
Cron Expression Formatting
For more information on the cron expression parsing, see the docs for robfig/cron.
Caveats
Dockron is quite simple right now. It does not yet:
- Issue any retries
- Cancel hanging jobs
I intend to keep it simple as well. It will likely never:
- Provide any kind of alerting (check out Minitor)
- Handle job dependencies
Either use a separate tool in conjunction with Dockron, or use a more robust scheduler like Tron, or Chronos.
Building
If you have go on your machine, you can simply use make build or make run to build and test Dockron. If you don't have go but you do have Docker, you can still build docker images using the provide multi-stage Dockerfile! You can kick that off with make docker-staged-build