A WIP README

Need a good project and app name
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IamTheFij 2018-08-03 16:56:22 -07:00
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WIP for a docker batch scheduler
Uses https://godoc.org/github.com/robfig/cron for cron expressions.
## Usage
Sets schedules based on label `cron.schedule="* * * * *"`
$APPNAME 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 $APPNAME
As simple as:
./$APPNAME
It will then run in the foreground, periodically checking Docker for containers with labels containing a cron schedule.
$APPNAME will periodically poll Docker for new containers or schedule changes.
### Scheduling a container
First, be sure your container is something that is not long running and will actually exit when complete. This is for batch runs and not keeping a service running. Docker should be able to do that on it's own with a restart policy.
Create your container and add a label in the form `$APPNAME.cron.schedule="* * * * *"`, where the value is a valid cron expression (See the section [Cron Expression Formatting](#cron-expression-formatting)).
$APPNAME 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](https://godoc.org/github.com/robfig/cron).
## Caveats
$APPNAME 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](https://git.iamthefij.com/IamTheFij/minitor))
* Handle job dependencies
Either use a separate tool in conjunction with $APPNAME, or use a more robust scheduler like Tron, or Chronos.