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https://issues.apache.org/jira/browse/HDFS-2379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13125402#comment-13125402
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Suresh Srinivas commented on HDFS-2379:
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FSDatasetInterface.java
# getBlockReport() javadoc is unnecessary.
# minor: "Request that an block report" -> "Request that a "
# retrieveAsyncBlockReport - javadoc is not very clear. Also change to javadoc
of getBlockReport() is not necessary.
FSDataset.java
# Indentation of {{String metaPart = ...}} could be better.
# Why do you want to deprecate #getBlockInfo()? If you have a valid reason, can
you please add information on the new method/mechanism that should be used
instead of the deprecated method.
# Make asyncBlockReport final.
# Why do you choose to notifyAll when requested is set to true, but not when
scan is set to null or requested is set to false?
# AsyncBlockReport#run - Why are you sleeping for 2 seconds on catching
Throwable?
# (!requested || scan != null) is better readable as !(requested && scan ==
null)
Datanode.java
# Optional - This might be a good time to move some of the block reported code
into a separate method, outside offerService().
> 0.20: Allow block reports to proceed without holding FSDataset lock
> -------------------------------------------------------------------
>
> Key: HDFS-2379
> URL: https://issues.apache.org/jira/browse/HDFS-2379
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node
> Affects Versions: 0.20.206.0
> Reporter: Todd Lipcon
> Priority: Critical
> Attachments: hdfs-2379.txt, hdfs-2379.txt, hdfs-2379.txt,
> hdfs-2379.txt, hdfs-2379.txt
>
>
> As disks are getting larger and more plentiful, we're seeing DNs with
> multiple millions of blocks on a single machine. When page cache space is
> tight, block reports can take multiple minutes to generate. Currently, during
> the scanning of the data directories to generate a report, the FSVolumeSet
> lock is held. This causes writes and reads to block, timeout, etc, causing
> big problems especially for clients like HBase.
> This JIRA is to explore some of the ideas originally discussed in HADOOP-4584
> for the 0.20.20x series.
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