Erik Krogen created HDFS-14370:
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Summary: 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
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.
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