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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2770) ZooKeeper slow operation log
Date Sat, 21 Oct 2017 15:48:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16213978#comment-16213978

ASF GitHub Bot commented on ZOOKEEPER-2770:

Github user eribeiro commented on a diff in the pull request:

    --- Diff: src/java/main/org/apache/zookeeper/server/ServerStats.java ---
    @@ -21,17 +21,32 @@
     import org.apache.zookeeper.common.Time;
    +import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +import java.util.Timer;
    +import java.util.TimerTask;
      * Basic Server Statistics
     public class ServerStats {
    +    private static final Logger LOG = LoggerFactory.getLogger(ServerStats.class);
         private long packetsSent;
         private long packetsReceived;
         private long maxLatency;
         private long minLatency = Long.MAX_VALUE;
         private long totalLatency = 0;
         private long count = 0;
    +    private long numRequestsAboveThresholdTime = 0;
    +    final static long requestWarnThresholdMs = QuorumPeerConfig.getRequestWarnResponseThresholdMs();
    +    final static Timer timer = new Timer();
    +    volatile Boolean waitForLoggingWarnThresholdMsg = false;
    --- End diff --
    Oh, excuse me, I got it. It's because you are synchronizing on it, right? Well, it's not
recommended (anti-pattern) to synchronize on non-final fields. Didn't Findbugs raised a warning
about this?

> 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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