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Date: Fri, 1 Jul 2016 10:45:11 +0000 (UTC)
From: "Vishal Khandelwal (JIRA)" <jira@apache.org>
To: dev@zookeeper.apache.org
Message-ID: <JIRA.12979354.1465995386000.3655.1467369911081@Atlassian.JIRA>
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Subject: [jira] [Commented] (ZOOKEEPER-2447) Zookeeper adds  good delay when
 one of the quorum host is not reachable
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archived-at: Fri, 01 Jul 2016 10:45:13 -0000


    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15358775#comment-15358775 ] 

Vishal Khandelwal commented on ZOOKEEPER-2447:
----------------------------------------------

[~eribeiro] : I will also be happy to look at the fix. It's always good to fix the problem in the right fashion. I also got the limitation of  "InetAddress#isReachable()" method wrt firewall but could not find a better solution for that. even with socket connect in my case did not work :(.

There would additional requirement of changing the design little as there is not provision to add the failed host back into the list yet. I opened JIRA here but did not get time to work on that :  ZOOKEEPER-2449 May be [~dbenediktson] fix will help to get rid of "ZOOKEEPER-2449" as well.

> Zookeeper adds  good delay when one of the quorum host is not reachable
> -----------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2447
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2447
>             Project: ZooKeeper
>          Issue Type: Bug
>    Affects Versions: 3.4.6, 3.5.0
>            Reporter: Vishal Khandelwal
>            Assignee: Vishal Khandelwal
>             Fix For: 3.5.3, 3.6.0
>
>         Attachments: ZOOKEEPER-2447.3.5.patch, withfix.txt, withoutFix.txt
>
>
> StaticHostProvider --> resolveAndShuffle method adds all of the address which are valid in the quorum to the list, shuffles them and sends back to client connection class. If after shuffling if first node appear to be the one which is not reachable, Clientcnx.SendThread.run will keep on connecting to the failure till a timeout and the moves to a different node. This adds up random delay in zookeeper connection in case a host is down. Rather we could check if host is reachable in StaticHostProvider and ignore isReachable is false. Same as we do for UnknownHostException Exception.
> This can tested using following test code by providing a valid host which is not reachable. for quick test comment Collections.shuffle(tmpList, sourceOfRandomness); in StaticHostProvider.resolveAndShuffle
> {code}
>  @Test
>   public void test() throws Exception {
>     EventsWatcher watcher = new EventsWatcher();
>     QuorumUtil qu = new QuorumUtil(1);
>     qu.startAll();
>     
>     ZooKeeper zk =
>         new ZooKeeper("<hostnamet:2181," + qu.getConnString(), 180 * 1000, watcher);
>     
>     watcher.waitForConnected(CONNECTION_TIMEOUT * 5);
>     Assert.assertTrue("connection Established", watcher.isConnected());
>     zk.close();    
>   }
> {code}
> Following fix can be added to StaticHostProvider.resolveAndShuffle
> {code}
>  if(taddr.isReachable(4000 // can be some value)) {
>                       tmpList.add(new InetSocketAddress(taddr, address.getPort()));
>                     } 
> {code}


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