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Posted to hdfs-issues@hadoop.apache.org by "Erik Krogen (JIRA)" <ji...@apache.org> on 2019/08/13 15:33:00 UTC
[jira] [Commented] (HDFS-14276) [SBN read] Reduce tailing overhead
[ https://issues.apache.org/jira/browse/HDFS-14276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16906314#comment-16906314 ]
Erik Krogen commented on HDFS-14276:
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[~ayushtkn] if you're still interested in this I think it's safe for you to take it from Wei-Chiu at this point :)
> [SBN read] Reduce tailing overhead
> ----------------------------------
>
> Key: HDFS-14276
> URL: https://issues.apache.org/jira/browse/HDFS-14276
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: ha, namenode
> Affects Versions: 3.3.0
> Environment: Hardware: 4-node cluster, each node has 4 core, Xeon 2.5Ghz, 25GB memory.
> Software: CentOS 7.4, CDH 6.0 + Consistent Reads from Standby, Kerberos, SSL, RPC encryption + Data Transfer Encryption.
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Priority: Major
> Attachments: HDFS-14276.000.patch, Screen Shot 2019-02-12 at 10.51.41 PM.png, Screen Shot 2019-02-14 at 11.50.37 AM.png
>
>
> When Observer sets {{dfs.ha.tail-edits.period}} = {{0ms}}, it tails edit log continuously in order to fetch the latest edits, but there is a lot of overhead in doing so.
> Critically, edit log tailer should _not_ update NameDirSize metric every time. It has nothing to do with fetching edits, and it involves lots of directory space calculation.
> Profiler suggests a non-trivial chunk of time is spent for nothing.
> Other than this, the biggest overhead is in the communication to serialize/deserialize messages to/from JNs. I am looking for ways to reduce the cost because it's burning 30% of my CPU time even when the cluster is idle.
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