> Given that RackAwareEnsemble policy defaults to finding a replacement > bookie within > the same rack, when a bookie is lost in a rack, the entire cluster will be > replicating > to the same 'rack'. This puts a lot of pressure on the rack and also takes > a longer time > to bring up the replication levels.
I agree this has potential to be problematic. Perhaps we should provide a switch to RackAwareEnsemble, 'preferReplaceInSameRack'. > I would think the right fix is to bring back the targetBookie concept (with > a configuration parameter) and add placement check predicate on top of it. > When this is configured > each bookie picks up the work, checks if the ensemble placement policy > gets satisfied, > if so replicate it, if not move on. I don't think adding a predicate argument (I guess a BiPredicate<Set<BookieSocketAddress>, BookieSocketAddress>?) to the recover bookie call makes sense. There is already a way to customize this behaviour, by passing in a EnsemblePlacementPolicy on Configuration of the client. The behaviour you want can be achieved by taking one of the current EnsemblePlacementPolicies and overriding replaceBookie, though I guess that's not very user-friendly. However, even if it was user-friendly, how would we make it easy for users to supply a placementpolicy or a even a predicate, as you suggested, to the autorecovery daemon. -Ivan
