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The rebalance mode used for this resource is FULL-AUTO mode. Thus, administrators don’t need to maintain a list of controller hosts in the ideal state. This new resource is auto-rebalancing. Once a controller is shutdown, it will be removed from the lead controller resource. Thus, it’s easy for administrators to add/remove/swap controller hosts with least effort. Plus, this resource leverages CRUSH-ed rebalance strategy, which provides more even partition distribution so that all the Pinot controllers can be in master state evenly across all the partitions. The default delayed rebalance time is set to 5 minutes, which means if some Pinot controller host goes offline, Helix cluster will wait at most 5 minutes for this controller to recover. If timeout is met, Helix cluster will elect a new master. The benefit of having this 5-minute delay is that it won't be too often to switch leadership (e.g. when restarting all the controller hosts one by one, it won't take 5 minutes to finish the restart). Plus, since some periodic tasks run more frequently, 5 minutes isn't a too long number so that Helix cluster can take action to elect a new leader shortlytimely.
Controller Modes
There’re 3 different modes to run controllers, i.e. dual mode, Helix only, and Pinot only.
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