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Date: Mon, 17 Jul 2017 03:55:00 +0000 (UTC)
From: "ASF GitHub Bot (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (ZOOKEEPER-2770) ZooKeeper slow operation log
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archived-at: Mon, 17 Jul 2017 03:55:07 -0000


    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2770?page=3Dcom.atlas=
sian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D=
16089282#comment-16089282 ]=20

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

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

    https://github.com/apache/zookeeper/pull/307#discussion_r127627805
 =20
    --- Diff: src/java/test/org/apache/zookeeper/server/ZooKeeperServerMain=
Test.java ---
    @@ -138,14 +145,56 @@ void delete(File f) throws IOException {
             ServerCnxnFactory getCnxnFactory() {
                 return main.getCnxnFactory();
             }
    +
         }
    =20
    -    public static  class TestZKSMain extends ZooKeeperServerMain {
    +    public static class TestZKSMain extends ZooKeeperServerMain {
    +
    +        private ServerStats serverStats;
    +
    +        @Override
    +        public ZooKeeperServer getZooKeeperServer(FileTxnSnapLog txnLo=
g, ServerConfig config, ZKDatabase zkDb) {
    +            ZooKeeperServer zooKeeperServer =3D super.getZooKeeperServ=
er(txnLog, config, zkDb);
    +            serverStats =3D zooKeeperServer.serverStats();
    +            return zooKeeperServer;
    +        }
    +
    +        @Override
             public void shutdown() {
                 super.shutdown();
             }
         }
    =20
    +    // Test for ZOOKEEPER-2770 ZooKeeper slow operation log
    +    @Test
    +    public void testRequestWarningThreshold() throws IOException, Keep=
erException, InterruptedException {
    +        ClientBase.setupTestEnv();
    +
    +        final int CLIENT_PORT =3D PortAssignment.unique();
    +
    +        MainThread main =3D new MainThread(CLIENT_PORT, true, null, 0)=
;
    +        main.start();
    +
    +        Assert.assertTrue("waiting for server being up",
    +                ClientBase.waitForServerUp("127.0.0.1:" + CLIENT_PORT,
    +                        CONNECTION_TIMEOUT));
    +        // Get the stats object from the ZooKeeperServer to keep track=
 of high latency requests.
    +        ServerStats stats =3D main.main.serverStats;
    +
    +        ZooKeeper zk =3D new ZooKeeper("127.0.0.1:" + CLIENT_PORT,
    +                ClientBase.CONNECTION_TIMEOUT, this);
    +
    +        zk.create("/foo1", "foobar".getBytes(), Ids.OPEN_ACL_UNSAFE,
    +                CreateMode.PERSISTENT);
    +
    +        Assert.assertEquals(new String(zk.getData("/foo1", null, null)=
), "foobar");
    +        // It takes a while for the counter to get updated sometimes, =
this is added to reduce flakyness
    +        Thread.sleep(1000);
    --- End diff --
   =20
    wondering why... =F0=9F=A4=94 I have run this test case a couple of tim=
es, but was unable to see this lag in counter updated manifested as asserti=
on failure. Did you see this consistently?


> 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 wh=
y any given read or write operation may become slow: a software bug, a prot=
ocol 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 ca=
use. However in order to diagnose intermittent problems we often don't know=
 where, or when, to begin looking. We need some sort of timestamped indicat=
ion of the problem. Although ZooKeeper is not a datastore, it does persist =
data, and can suffer intermittent performance degradation, and should consi=
der implementing a 'slow query' log, a feature very common to services whic=
h persist information on behalf of clients which may be sensitive to latenc=
y 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 req=
uest is beyond a configured threshold.=20
> Look at the HBase {{responseTooSlow}} feature for inspiration.=20


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