Task management by Overlord, Middle Manager and Peon

Apache Druid Q&A Google Groups
#1

I was trying to understand how task management works in druid. Specifically real-time tasks.

My understanding is:

  1. Whenever tranquility wants to create a real-time task, the task is submitted to overlord

  2. Overlord can run tasks in two modes: remote and local

  • If druid.indexer.runner.type=local, then Overlord would spawn a Peon itself and run the task. In this case Middle Managers are not involved

  • If druid.indexer.runner.type=remote, then overlord uses Middle manager to distribute tasks across them. Peons would then be scheduled/run by Middle Managers

Can someone validate this?

  • For using druid.indexer.runner.type=remote , the druid cluster must have Middle Managers

I am actually facing issues while setting up a Druid cluster wherein, i see tasks getting created when using druid.indexer.runner.type=local and no tasks are created when druid.indexer.runner.type=remote with application throwing “Failed to create merged beam: druid:overlord/pageviews”. Could this be due to the fact that overlord is not able to leverage Middle Managers?

Thanks,

Prathamesh

#2

Hi Prathmesh,
yes your understanding is absolutely correct.

I guess when you are running in remote mode, probably the middlemanager configs are incorrect and causes the tasks to fail.

Check overlord, middlemanager and any task logs for failures.