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From "Ewen Cheslack-Postava (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (KAFKA-3135) Unexpected delay before fetch response transmission
Date Sat, 31 Dec 2016 01:21:58 GMT

     [ https://issues.apache.org/jira/browse/KAFKA-3135?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ewen Cheslack-Postava updated KAFKA-3135:
-----------------------------------------
    Affects Version/s: 0.10.1.0
                       0.9.0.1
                       0.10.0.0
                       0.10.0.1
                       0.10.1.1

> Unexpected delay before fetch response transmission
> ---------------------------------------------------
>
>                 Key: KAFKA-3135
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3135
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 0.9.0.0, 0.10.1.0, 0.9.0.1, 0.10.0.0, 0.10.0.1, 0.10.1.1
>            Reporter: Jason Gustafson
>            Assignee: Jason Gustafson
>            Priority: Critical
>             Fix For: 0.10.2.0
>
>
> From the user list, Krzysztof Ciesielski reports the following:
> {quote}
> Scenario description:
> First, a producer writes 500000 elements into a topic
> Then, a consumer starts to read, polling in a loop.
> When "max.partition.fetch.bytes" is set to a relatively small value, each
> "consumer.poll()" returns a batch of messages.
> If this value is left as default, the output tends to look like this:
> Poll returned 13793 elements
> Poll returned 13793 elements
> Poll returned 13793 elements
> Poll returned 13793 elements
> Poll returned 0 elements
> Poll returned 0 elements
> Poll returned 0 elements
> Poll returned 0 elements
> Poll returned 13793 elements
> Poll returned 13793 elements
> As we can see, there are weird "gaps" when poll returns 0 elements for some
> time. What is the reason for that? Maybe there are some good practices
> about setting "max.partition.fetch.bytes" which I don't follow?
> {quote}
> The gist to reproduce this problem is here: https://gist.github.com/kciesielski/054bb4359a318aa17561.
> After some initial investigation, the delay appears to be in the server's networking
layer. Basically I see a delay of 5 seconds from the time that Selector.send() is invoked
in SocketServer.Processor with the fetch response to the time that the send is completed.
Using netstat in the middle of the delay shows the following output:
> {code}
> tcp4       0      0  10.191.0.30.55455      10.191.0.30.9092       ESTABLISHED
> tcp4       0 102400  10.191.0.30.9092       10.191.0.30.55454      ESTABLISHED
> {code}
> From this, it looks like the data reaches the send buffer, but needs to be flushed.



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