[jira] [Created] (HELIX-540) Full-auto rebalancer not able to map all partitions

["Zhen Zhang (JIRA)" <ji...@apache.org>]

Zhen Zhang created HELIX-540:
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             Summary: Full-auto rebalancer not able to map all partitions 
                 Key: HELIX-540
                 URL: https://issues.apache.org/jira/browse/HELIX-540
             Project: Apache Helix
          Issue Type: Bug
            Reporter: Zhen Zhang


We discover a bug where full-auto rebalancer not be able to mapping all partitions even when capacity is enough.

Assuming we have 2 partition and 2 node, state model is LeaderStandby and replica is 1. For some reason, the current state mapping becomes:
{noformat}
partition_0:
  node_0: LEADER
  node_1: STANDBY
{noformat}

The extra STANDBY mapping prevents the full-auto rebalancer (AutoRebalanceStrategy#computePartitionAssignment) to assign LEADER to partition_1, so partition_1 will remain unmapped even though node capacity is enough.

For workaround, we can disable the partition in STANDBY state on the node, thus "frees" the quota and the unmapped partition will get assigned LEADER. We can then re-enable the partition on the node.





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