gianm commented on issue #7447: Coordinator: Allow dropping all segments. URL: https://github.com/apache/incubator-druid/pull/7447#issuecomment-483785429 @leventov, sorry, what question do you mean? Is it whether or not we should stop polling the DB after losing leadership? (https://github.com/apache/incubator-druid/pull/7447#issuecomment-482249849) I can only think of one benefit of nullifying the metadata segment cache when losing leadership: it means that next time we gain leadership, we're guaranteed that the segment cache we use is _at least as new_ as the gain of leadership. If we might use an old one, there's a potential for a new leader to use an older view of segments than the old leader. It could be extreme: maybe the new leader, for some reason, hasn't been able to poll for hours or even days, leading to surprising behavior as the cluster 'rolls back' to an earlier state. This could be mitigated through some code that explicitly makes sure the currently-cached segment metadata is at least as new as the leadership gain, though. I think if you decide it's best to stop nullifying the cache, it'd be good to also add this safety mechanism.
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