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https://issues.apache.org/jira/browse/HDFS-12943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16724465#comment-16724465
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Chen Liang commented on HDFS-12943:
-----------------------------------
Hi [~brahmareddy]
bq. you can see this issue if "dfs.ha.tail-edits.period" is default value.
Yes, with default period of 1min, any read can take up to 1min to finish, this
is not specific to "second" call as you were mentioning, but any read. I agree
that we need to lower this value. In our environment, we do already have set it
to 100ms, and with this setting, I never seen the issue of always the second
call timeout as you mentioned, nor getServiceState taking 2 seconds. I was
under the impression that you still had the timeout even with setting it to
100ms?
> Consistent Reads from Standby Node
> ----------------------------------
>
> Key: HDFS-12943
> URL: https://issues.apache.org/jira/browse/HDFS-12943
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: hdfs
> Reporter: Konstantin Shvachko
> Priority: Major
> Attachments: ConsistentReadsFromStandbyNode.pdf,
> ConsistentReadsFromStandbyNode.pdf, HDFS-12943-001.patch,
> HDFS-12943-002.patch, TestPlan-ConsistentReadsFromStandbyNode.pdf
>
>
> StandbyNode in HDFS is a replica of the active NameNode. The states of the
> NameNodes are coordinated via the journal. It is natural to consider
> StandbyNode as a read-only replica. As with any replicated distributed system
> the problem of stale reads should be resolved. Our main goal is to provide
> reads from standby in a consistent way in order to enable a wide range of
> existing applications running on top of HDFS.
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