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https://issues.apache.org/jira/browse/HDFS-14370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16894392#comment-16894392
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Ayush Saxena edited comment on HDFS-14370 at 7/27/19 10:15 AM:
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Thanx [~xkrogen] for the patch, Seems fair enough,
A doubt, Is there any way to turn off this back-off mechanism? as if my
requirement doesn't want me to have a backoff, usually we configure 0 interval
for tailing edits for very loaded clusters, it may reach to a backoff stage may
be easily, if for fractions the load is nil.
And secondly if I don't configure the back-off time, The default it shall take
as 1 Min, so if my in general time is 0, the next shall get triggered at 1 Min,
I guess by default we should keep the back-off disabled and the value of
max-backoff to be same as that of sleeptimeMs if the max-backoff time isn't
specified.
was (Author: ayushtkn):
Thanx [~xkrogen] for the patch, Seems fair enough,
A doubt, Is there any way to turn off this back-off mechanism? as if my
requirement doesn't want me to have a backoff, usually we configure 0 interval
for tailing edits for very loaded clusters, it may reach to a backoff stage may
be easily, if for fractions the load is nil.
And secondly if I don't configure the back-off time, The default it shall take
and 1 Min, so if my in general time is 0, the next shall get triggered at 1
Min, I guess by default we shouldn't keep the back-off disabled and the value
of max-backoff to be same as that of sleeptimeMs if the max-backoff time isn't
specified.
> Edit log tailing fast-path should allow for backoff
> ---------------------------------------------------
>
> Key: HDFS-14370
> URL: https://issues.apache.org/jira/browse/HDFS-14370
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, qjm
> Affects Versions: 3.3.0
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Major
> Attachments: HDFS-14370.000.patch
>
>
> As part of HDFS-13150, in-progress edit log tailing was changed to use an
> RPC-based mechanism, thus allowing the edit log tailing frequency to be
> turned way down, and allowing standby/observer NameNodes to be only a few
> milliseconds stale as compared to the Active NameNode.
> When there is a high volume of transactions on the system, each RPC fetches
> transactions and takes some time to process them, self-rate-limiting how
> frequently an RPC is submitted. In a lightly loaded cluster, however, most of
> these RPCs return an empty set of transactions, consuming a high
> (de)serialization overhead for very little benefit. This was reported by
> [~jojochuang] in HDFS-14276 and I have also seen it on a test cluster where
> the SbNN was submitting 8000 RPCs per second that returned empty.
> I propose we add some sort of backoff to the tailing, so that if an empty
> response is received, it will wait a longer period of time before submitting
> a new RPC.
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