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https://issues.apache.org/jira/browse/HDFS-14370?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Erik Krogen updated HDFS-14370:
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Description:
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.
was:
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 reported 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.
> 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
>
> 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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