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Posted to hdfs-issues@hadoop.apache.org by "Wei-Chiu Chuang (JIRA)" <ji...@apache.org> on 2016/11/20 19:42:59 UTC
[jira] [Updated] (HDFS-11160) VolumeScanner reports
write-in-progress replicas as corrupt incorrectly
[ https://issues.apache.org/jira/browse/HDFS-11160?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Wei-Chiu Chuang updated HDFS-11160:
-----------------------------------
Summary: VolumeScanner reports write-in-progress replicas as corrupt incorrectly (was: VolumeScanner incorrectly reports good replicas as corrupt due to race condition)
> VolumeScanner reports write-in-progress replicas as corrupt incorrectly
> -----------------------------------------------------------------------
>
> Key: HDFS-11160
> URL: https://issues.apache.org/jira/browse/HDFS-11160
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Environment: CDH5.7.4
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Attachments: HDFS-11160.reproduce.patch
>
>
> Due to a race condition initially reported in HDFS-6804, VolumeScanner may erroneously detect good replicas as corrupt. This is serious because in some cases it results in data loss if all replicas are declared corrupt.
> We are investigating an incidence that caused very high block corruption rate in a relatively small cluster. Initially, we thought HDFS-11056 is to blame. However, after applying HDFS-11056, we are still seeing VolumeScanner reporting corrupt replicas.
> It turns out that if a replica is being appended while VolumeScanner is scanning it, VolumeScanner may use the new checksum to compare against old data, causing checksum mismatch.
> I have a unit test to reproduce the error. Will attach later.
> To fix it, I propose a FinalizedReplica object should also have a lastChecksum field like ReplicaBeingWritten, and BlockSender should use the in-memory lastChecksum to verify the partial data in the last chunk on disk. File this jira to discuss a good fix for this issue.
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