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From "Yicheng Fang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2899) Zookeeper not receiving packets after ZXID overflows
Date Thu, 05 Oct 2017 18:19:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16193369#comment-16193369
] 

Yicheng Fang commented on ZOOKEEPER-2899:
-----------------------------------------

[~maoling] NaH, I have since shifted focus to other tasks because it didn't seem like I was
getting close to reproducing what we saw in prod.

It would be great if you have some ideas that we can try out. We're all ears.

> Zookeeper not receiving packets after ZXID overflows
> ----------------------------------------------------
>
>                 Key: ZOOKEEPER-2899
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2899
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: leaderElection
>    Affects Versions: 3.4.5
>         Environment: 5 host ensemble, 1500+ client connections each, 300K+ nodes
> OS: Ubuntu precise
> JAVA 7
> JuniperQFX510048T NIC, 10000Mb/s, ixgbe driver
> 6 core Intel(R)_Xeon(R)_CPU_E5-2620_v3_@_2.40GHz
> 4 HDD 600G each 
>            Reporter: Yicheng Fang
>         Attachments: GC_metric.png, image12.png, image13.png, message_in_per_sec.png,
metric_volume.png, zk_20170309_wo_noise.log
>
>
> ZK was used with Kafka (version 0.10.0) for coordination. We had a lot of Kafka consumers
writing  consumption offsets to ZK.
> We observed the issue two times within the last year. Each time after ZXID overflowed,
ZK was not receiving packets even though leader election looked successful from the logs,
and ZK servers were up. As a result, the whole Kafka system came to a halt.
> As an attempt to reproduce (and hopefully fixing) the issue, I set up test ZK and Kafka
clusters and feed them with like-production test traffic. Though not really able to reproduce
the issue, I did see that the Kafka consumers, which used ZK clients, essentially DOSed the
ensemble, filling up the `submittedRequests` in `PrepRequestProcessor`, causing even 100ms+
read latencies.
> More details are included in the comments.



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