You may have seen a repo in our Github organization called job-scheduler. The Open Distro for Elasticsearch Job Scheduler provides an extendable framework for Elasticsearch plugin developers to run custom jobs on Elasticsearch. For example, you might want to write a plugin which runs an aggregation query against raw data and save the aggregated data into a new index every hour, or you might want to write a plugin which periodically polls metrics in Elasticsearch and posts the results to a Webhook.
The inspiration of the Job Scheduler plugin came from building our Alerting plugin. During the development effort to build scheduled monitors and triggers, we realized that we could build a framework to make it easy for other Elasticsearch plugins to be able to schedule and manage jobs.