Container Once Retention Strategy
For each job in the queue, an own docker container is started. Once the job has finished, the container is shut down.
Container Idle Retention Strategy
Based on the workload provided by the queue (load average), new docker containers are started on demand. After the job(s) have finished, the container is not shut down immediately.
If no new job was executed on this slave/container during the period of the Idle delay, the container is shut down.