Indexing create (and sometimes destroy) Druid segments. The indexing service has a master/slave like architecture.

The indexing service is composed of three main components: a component that can run a single task, a Middle Manager component that manages Peons, and an component that manages task distribution to MiddleManagers. Overlords and MiddleManagers may run on the same process or across multiple processes while MiddleManagers and Peons always run on the same process.

See Overlord.

See .

See Tasks.