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https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16219919#comment-16219919
 ] 

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_r147040783
  
    --- Diff: src/java/main/org/apache/zookeeper/server/ServerStats.java ---
    @@ -148,9 +174,46 @@ synchronized public void resetRequestCounters(){
             packetsReceived = 0;
             packetsSent = 0;
         }
    +    synchronized public void resetNumRequestsAboveThresholdTime() {
    +        numRequestsAboveThresholdTime = 0;
    +    }
         synchronized public void reset() {
             resetLatency();
             resetRequestCounters();
    +        resetNumRequestsAboveThresholdTime();
    +    }
    +
    +    public void checkLatency(final ZooKeeperServer zks, Request request) {
    +        long requestLatency = Time.currentElapsedTime() - 
request.createTime;
    +        boolean enabledAndAboveThreshold = (requestWarnThresholdMs == 0) ||
    +                (requestWarnThresholdMs > -1 && requestLatency > 
requestWarnThresholdMs);
    +        if (enabledAndAboveThreshold) {
    +            zks.serverStats().incNumRequestsAboveThresholdTime();
    +
    +            // Try acquiring lock only if not waiting
    +            boolean success = 
waitForLoggingWarnThresholdMsg.compareAndSet(Boolean.FALSE, Boolean.TRUE);
    +            if(success) {
    --- End diff --
    
    Need a space between if and (


> 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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