mongodb runtime_error ai_generated true

MongoServerError: balancer round migration failed: chunk migration failed for namespace mydb.mycoll

ID: mongodb/balancer-round-migration-failure

Also available as: JSON · Markdown · 中文
85%Fix Rate
88%Confidence
1Evidence
2023-11-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
MongoDB 7.0 active — — —
MongoDB 6.0 active — — —
MongoDB 8.0 (early access) active — — —

Root Cause

The balancer failed to migrate a chunk due to a temporary network issue or a conflicting operation on the source or target shard.

generic

中文

由于临时网络问题或源/目标分片上的冲突操作，均衡器无法迁移块。

Workarounds

  1. 75% success Check balancer state and retry migration after resolving any conflicting operations (e.g., long-running queries or index builds). Use sh.status() to monitor balancer activity. 
    Check balancer state and retry migration after resolving any conflicting operations (e.g., long-running queries or index builds). Use sh.status() to monitor balancer activity.
  2. 80% success Increase balancer window or reduce chunk size to make migrations more manageable: use sh.setBalancerState(true) and adjust chunk size via sh._setBalancerChunkSize(64) (in MB). 
    Increase balancer window or reduce chunk size to make migrations more manageable: use sh.setBalancerState(true) and adjust chunk size via sh._setBalancerChunkSize(64) (in MB).
  3. 85% success Force chunk migration manually using moveChunk with a specific shard key range and wait for completion: sh.moveChunk('mydb.mycoll', { shardKey: value }, 'targetShard'). 
    Force chunk migration manually using moveChunk with a specific shard key range and wait for completion: sh.moveChunk('mydb.mycoll', { shardKey: value }, 'targetShard').

中文步骤

  1. Check balancer state and retry migration after resolving any conflicting operations (e.g., long-running queries or index builds). Use sh.status() to monitor balancer activity.
  2. Increase balancer window or reduce chunk size to make migrations more manageable: use sh.setBalancerState(true) and adjust chunk size via sh._setBalancerChunkSize(64) (in MB).
  3. Force chunk migration manually using moveChunk with a specific shard key range and wait for completion: sh.moveChunk('mydb.mycoll', { shardKey: value }, 'targetShard').

Dead Ends

Common approaches that don't work:

  1. 60% fail

    moveChunk may fail with same error if underlying issue persists, and can disrupt ongoing migrations.

  2. 70% fail

    Stopping balancer is a temporary pause, not a fix; the root cause (e.g., network blip) remains.

  3. 50% fail

    Restart often doesn't resolve underlying connectivity or operation conflicts.