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From "Karan Mehta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2770) ZooKeeper slow operation log
Date Wed, 26 Jul 2017 03:25:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16101114#comment-16101114
] 

Karan Mehta commented on ZOOKEEPER-2770:
----------------------------------------

bq. Operations over 100ms should be vanishingly rare, but I wouldn't leap up to find out what
is happening. I would be fairly unhappy, though, and would start checking.
Let's take this as a motivation. :) 
With that said, is 300 ms a good value or even less is better?

> ZooKeeper slow operation log
> ----------------------------
>
>                 Key: ZOOKEEPER-2770
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2770
>             Project: ZooKeeper
>          Issue Type: Improvement
>            Reporter: Karan Mehta
>            Assignee: Karan Mehta
>         Attachments: ZOOKEEPER-2770.001.patch, ZOOKEEPER-2770.002.patch, ZOOKEEPER-2770.003.patch
>
>
> ZooKeeper is a complex distributed application. There are many reasons why any given
read or write operation may become slow: a software bug, a protocol problem, a hardware issue
with the commit log(s), a network issue. If the problem is constant it is trivial to come
to an understanding of the cause. However in order to diagnose intermittent problems we often
don't know where, or when, to begin looking. We need some sort of timestamped indication of
the problem. Although ZooKeeper is not a datastore, it does persist data, and can suffer intermittent
performance degradation, and should consider implementing a 'slow query' log, a feature very
common to services which persist information on behalf of clients which may be sensitive to
latency while waiting for confirmation of successful persistence.
> Log the client and request details if the server discovers, when finally processing the
request, that the current time minus arrival time of the request is beyond a configured threshold.

> Look at the HBase {{responseTooSlow}} feature for inspiration. 



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