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https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16219918#comment-16219918
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ASF GitHub Bot commented on ZOOKEEPER-2770:
-------------------------------------------
Github user tdunning commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/307#discussion_r147040873
--- Diff:
src/java/main/org/apache/zookeeper/server/FinalRequestProcessor.java ---
@@ -81,9 +81,11 @@
private static final Logger LOG =
LoggerFactory.getLogger(FinalRequestProcessor.class);
ZooKeeperServer zks;
+ ServerStats serverStats;
--- End diff --
I think that caching this reference is a bad practice. Getting a reference
every time costs essentially nothing and keeping a reference to a data
structure that we don't own is asking for trouble if anybody every reallocates
it.
> 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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