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  1. Core Server
  2. SERVER-29423

Sharding balancer schedules multiple migrations with the same conflicting source or destination

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 3.4.4
    • Fix Version/s: 3.4.11, 3.6.3, 3.7.2
    • Component/s: Sharding
    • Labels:
    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Backport Requested:
      v3.6, v3.4
    • Sprint:
      Sharding 2018-01-29
    • Case:

      Description

      The sharding balancer policy avoids producing multiple migrations for the same shard.

      However, the policy runs per collection and doesn't save any state across collections. Because of this, if there are multiple collections which need balancing, it may produce overlapping shards.

      There is no correctness problem with this, but it will cause useless ConflictingOperationInProgress errors to pollute the config server and shard's logs on each balancer round.

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                Updated:
                Resolved: