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https://issues.apache.org/jira/browse/HDFS-9901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15188501#comment-15188501
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Inigo Goiri commented on HDFS-9901:
-----------------------------------
The first version of the patch:
# Makes {{DF}} asynchronous when monitoring the disk by creating a thread that
checks the disk and updates the disk status periodically. Then the
{{FsVolumeImpl}} reads the values that are collected asynchronously.
# Makes the checks (which required disk accesses) in {{transferBlock()}} in
{{DataNode}} into a separate thread so the heartbeat does not have to wait for
this when heartbeating.
> Move block validation out of the heartbeat thread
> -------------------------------------------------
>
> Key: HDFS-9901
> URL: https://issues.apache.org/jira/browse/HDFS-9901
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Reporter: Hua Liu
> Assignee: Hua Liu
> Attachments:
> 0001-HDFS-9901-Move-block-validation-out-of-the-heartbeat.patch
>
>
> During heavy disk IO, we noticed hearbeat thread hangs on checkBlock method,
> which checks the existence and length of a block before spins off a thread to
> do the actual transferring. In extreme cases, the heartbeat thread hang more
> than 10 minutes so the namenode marked the datanode as dead and started
> replicating its blocks, which caused more disk IO on other nodes and can
> potentially brought them down.
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