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Ted Dunning commented on ZOOKEEPER-2770: ---------------------------------------- [~fournc], I am not so sure that *I* agree with me at this point. It is fair to say that on occasion there are slow operations in ZK and it would be good to know about them. This kind of problem is almost always due, in my own vicarious experience, to bad configuration. Often the bad configuration is simply collocation with a noisy neighbor on a deficient storage layer. There might be situations where an operation is slow due to the content of the query itself, but I cannot imagine what those situations might be. Writing a large value (but that is strictly limited in size), or even doing a huge multi-op (which has the same limited size in aggregate) should never take very long. As such, I would expect that the highest diagnostic value would not be something that dumped the contents of slow queries, but rather a capability that characterizes the entire distribution of query times. The frequency of slow queries is a diagnostic of sorts, but is one that could be inferred from the time-varying distributional information I was suggesting. That said, I don't think that a slow query log is a BAD thing (except a bit bad in terms of security if it logs the actual query). And I wouldn't want the BEST thing (a distribution log) to stop somebody contributing something. > 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. -- This message was sent by Atlassian JIRA (v6.4.14#64029)