[infinispan-issues] [JBoss JIRA] (ISPN-7461) Cache is not rebalanced on merge

[Dennis Reed (JIRA)]

Dennis Reed created ISPN-7461:
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             Summary: Cache is not rebalanced on merge
                 Key: ISPN-7461
                 URL: https://issues.jboss.org/browse/ISPN-7461
             Project: Infinispan
          Issue Type: Bug
          Components: State Transfer
    Affects Versions: 5.2.7.Final
            Reporter: Dennis Reed


After a cluster split and merge, the consistent hash is not balanced between the members.

For example in a 2-member cluster, after the merge one node will be primary owner of every segment.  In In a larger cluster, some nodes will not own any data.

DefaultConsistentHash{numSegments=60, numOwners=2, members=[RehashAfterPartitionMergeTest-NodeB-49100, RehashAfterPartitionMergeTest-NodeA-11552]} -- 0: 0 1, 1: 0 1, 2: 0 1, 3: 0 1, 4: 0 1, 5: 0 1, 6: 0 1, 7: 0 1, 8: 0 1, 9: 0 1, 10: 0 1, 11: 0 1, 12: 0 1, 13: 0 1, 14: 0 1, 15: 0 1, 16: 0 1, 17: 0 1, 18: 0 1, 19: 0 1, 20: 0 1, 21: 0 1, 22: 0 1, 23: 0 1, 24: 0 1, 25: 0 1, 26: 0 1, 27: 0 1, 28: 0 1, 29: 0 1, 30: 0 1, 31: 0 1, 32: 0 1, 33: 0 1, 34: 0 1, 35: 0 1, 36: 0 1, 37: 0 1, 38: 0 1, 39: 0 1, 40: 0 1, 41: 0 1, 42: 0 1, 43: 0 1, 44: 0 1, 45: 0 1, 46: 0 1, 47: 0 1, 48: 0 1, 49: 0 1, 50: 0 1, 51: 0 1, 52: 0 1, 53: 0 1, 54: 0 1, 55: 0 1, 56: 0 1, 57: 0 1, 58: 0 1, 59: 0 1

This is triggered consistently by the RehashAfterPartitionMergeTest test case, but is not caught because it does not sufficiently check the consistent hash.  (it checks RebalancePolicy.isBalanced, which merely makes sure each segment has the correct number of owners, not that it's evenly distributed).



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