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https://issues.apache.org/jira/browse/HDFS-9023?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiao Chen updated HDFS-9023:
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Attachment: HDFS-9023.03.patch
Thanks a lot Surendra.
1 and 2 done. Good idea about making the code simpler.
For #3, the purpose of this logs is to look at the reason behind the
placements, and by itself does not really 'warn' that there is anything wrong
with hdfs. Also it does not always necessarily mean things are wrong - an
example would be
{{TestDefaultBlockPlacementPolicy#testPlacementWithLocalRackNodesDecommissioned}}.
IMO info logs solve the problem of "when a placement failed, we don't know why
from the logs", without scaring admins.
So kept this as-is in patch 3. Please let me know if you feel otherwise.
> When NN is not able to identify DN for replication, reason behind it can be
> logged
> ----------------------------------------------------------------------------------
>
> Key: HDFS-9023
> URL: https://issues.apache.org/jira/browse/HDFS-9023
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client, namenode
> Affects Versions: 2.7.1
> Reporter: Surendra Singh Lilhore
> Assignee: Xiao Chen
> Priority: Critical
> Attachments: HDFS-9023.01.patch, HDFS-9023.02.patch,
> HDFS-9023.03.patch
>
>
> When NN is not able to identify DN for replication, reason behind it can be
> logged (at least critical information why DNs not chosen like disk is full).
> At present it is expected to enable debug log.
> For example the reason for below error looks like all 7 DNs are busy for data
> writes. But at client or NN side no hint is given in the log message.
> {noformat}
> File /tmp/logs/spark/logs/application_1437051383180_0610/xyz-195_26009.tmp
> could only be replicated to 0 nodes instead of minReplication (=1). There
> are 7 datanode(s) running and no node(s) are excluded in this operation.
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1553)
>
> {noformat}
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