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https://issues.apache.org/jira/browse/HBASE-11492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14058600#comment-14058600
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Nicolas Liochon commented on HBASE-11492:
-----------------------------------------
(on the bug)
I've tried different jdk7 versions, they all have the same behavior. If I
understand well Esteban tested the jdk6?
Searching in google I have
"channel.socket().setTcpNoDelay" => 4400 results
"channel.setOption(StandardSocketOptions.TCP_NODELAY" => 60 results
If it's representative, it could be classified as a documentation bug at the
very least I suppose.
But the jdk bug database contains nothing on this. On the web, multiple
documentations mention setOption with nio, without alerting that
channel.socket().setTcpNoDelay won't work. I haven't found anyone complaining
or alerting on this (well someone has to be the first :-) )
But yeah, it's a pure nio thing. with oio using the socket works (that's why
the hbase client sets nagle correctly for its side of the connection).
bq. Should we set both of these just in case if this is a JDK issue indeed?
In anycase using the setOption is fine. Requiring the socket.settcpnodelay
would be a regression.
bq. Wouldn't other TCP flags be affected in the same way too?
It seems not for the keep alive. I haven't tested in details however, so I may
be wrong.
bq. since HDFS + HBase always use this style, right?
I think it's because of the OIO thing: it works fine until you use the NIO.
As well, Nagle is tricky, because the first packet is sent immediately, the
wait is on the next ones. Nevertheless the issue is quite severe.
bq. so weird
That's for sure :-)
[~andrew.purt...@gmail.com] What about the 0.98? An intermediate patch would be
to default back the value to false if we fear that activating 'for real' the
nodelay would be too risky.
[~lhofhansl] fyi.
> The servers do not honor the tcpNoDelay option
> ----------------------------------------------
>
> Key: HBASE-11492
> URL: https://issues.apache.org/jira/browse/HBASE-11492
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.92.2, 0.98.0, 0.96.0, 0.99.0, 0.94.20
> Reporter: Nicolas Liochon
> Assignee: Nicolas Liochon
> Priority: Critical
> Fix For: 0.99.0, 0.98.5
>
> Attachments: 11492.v1.patch
>
>
> There is an option to set tcpNoDelay, defaulted to true, but the socket
> channel is actually not changed. As a consequence, the server works with
> nagle enabled. This leads to very degraded behavior when a single connection
> is shared between threads. We enter into conflicts with nagle and tcp delayed
> ack.
> Here is an example of performance with the PE tool plus HBASE-11491:
> {noformat}
> oneCon #client sleep exeTime (seconds)
> avg latency, sleep excluded (microseconds)
> true 1 0 31
> 310
> false 1 0 31
> 310
> true 2 0 50
> 500
> false 2 0 31
> 310
> true 2 5 488 (including 200s sleeping)
> 2880
> false 2 5 246 (including 200s sleeping)
> 460
> {noformat}
> The latency is multiple by 5 (2880 vs 460) when the connection is shared.
> This is the delayed ack kicking in. This can be fixed by really using tcp no
> delay.
> Any application sharing the tcp connection between threads has the issue.
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