HBASE-29072 StochasticLoadBalancer#areReplicasColocated ignores rack colocation #6622
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rmdmattingly
commented
Jan 21, 2025
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| int numReplicas = region.getReplicaId() + 1; | ||
| if (numReplicas > maxReplicas) { | ||
| maxReplicas = numReplicas; | ||
| } |
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This seemed like a very cheap way to determine the max replica count without actually seeing the table descriptors, which is a limitation of the current balancer implementation.
Sometime I would like to fix this limitation and make the balancer table descriptor aware, but I think that is its own problem
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| assertFalse(loadBalancer.needsBalance(HConstants.ENSEMBLE_TABLE_NAME, | ||
| new BalancerClusterState(map, null, null, new ForTestRackManagerOne()))); |
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In that PR where we made the balancer ignorant to rack colocation, we also just naively switched this assertion to false. But the intention of this test was always for the assertion to be true.
I've also split this test up into two tests, because it was always testing two distinct cases (host and rack colocation).
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This is yet another bite of #6593
In #3729 we removed consideration replicas' rack distribution. This was, in my opinion, a mistake — if we want to be flexible for environments that have too few racks, then we should just do so by skipping this check when the rack count is < the max replica count