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Posted to hdfs-dev@hadoop.apache.org by "Todd Lipcon (Created) (JIRA)" <ji...@apache.org> on 2012/02/17 21:56:57 UTC

[jira] [Created] (HDFS-2970) Contending block synchronizations can result in scary log messages

Contending block synchronizations can result in scary log messages
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                 Key: HDFS-2970
                 URL: https://issues.apache.org/jira/browse/HDFS-2970
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: data-node
    Affects Versions: 0.23.0
            Reporter: Todd Lipcon


If multiple datanodes are attempting to act as the coordinator for a block recovery, but one is being particularly slow, it's possible that you see the following interleaving:
- Primary A receives block recovery command for recovery genstamp = 1, then starts acting slow
- Primary B receives block recovery command for recovery genstamp = 2
- Primary B calls initReplicaRecovery on other nodes for genstamp = 2
- Primary A calls initReplicaRecovery on other nodes for genstamp = 1
This results in a scary message. For example:

java.io.IOException: java.io.IOException: THIS IS NOT SUPPOSED TO HAPPEN: replica.getGenerationStamp() >= recoveryId = 4148, block=blk_6899379920748342698_4136, replica=FinalizedReplica, blk_6899379920748342698_4176, FINALIZED

BUT, this scenario is properly handled by the recovery protocol. We should tone down the message a bit.

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