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https://issues.apache.org/jira/browse/HDFS-15789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17273129#comment-17273129
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Kihwal Lee commented on HDFS-15789:
-----------------------------------
This is a safe change.
The FSN lock is only protecting NN against renewing a lease during a HA
transition, which should be done by only the active NN. So after this patch,
there can be a case where a lease renewal request is received and being
processed while a NN is active, but finishes processing it during or after
transitioning to standby. However, this does not affect the file system
consistency or violate the existing file system API semantics. The important
states are whether file is open and who has the lease. Anything that changes
these states is edit-logged. The renewal does not revive expired/revoked
leases and is thus not edit-logged.
+1 for the patch.
> Lease renewal does not require namesystem lock
> ----------------------------------------------
>
> Key: HDFS-15789
> URL: https://issues.apache.org/jira/browse/HDFS-15789
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Affects Versions: 3.4.0
> Reporter: Jim Brennan
> Assignee: Jim Brennan
> Priority: Major
> Attachments: HDFS-15789.001.patch
>
>
> [~daryn] found this while testing the performance for HDFS-15704.
> The lease manager is independent of the namesystem. Acquiring the lock causes
> unnecessary lock contention that degrades throughput.
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