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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2770) ZooKeeper slow operation log
Date Wed, 22 Nov 2017 02:40:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16261884#comment-16261884
] 

ASF GitHub Bot commented on ZOOKEEPER-2770:
-------------------------------------------

Github user skamille commented on the issue:

    https://github.com/apache/zookeeper/pull/307
  
    I appreciate the work that you are trying to do here, and this still feels like an incomplete
approach to a problem that would be worth investing further into. It seems like we all agree
that it would be good to have clearer metrics about the performance behavior of the internals
of the system. This implements some basic infrastructure for a metric recording framework,
coupled to the recording of one metric. Can we at least make it so that the process of "push
a metric to a buffer, have a thread that wakes up periodically and flushes information out
of that buffer" is usable by multiple parts of the system, instead of coupling it to the one
metric of request time?


> 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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