zookeeper-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Flavio Junqueira (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2447) Zookeeper adds good delay when one of the quorum host is not reachable
Date Wed, 03 Aug 2016 17:03:20 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15406224#comment-15406224
] 

Flavio Junqueira commented on ZOOKEEPER-2447:
---------------------------------------------

[~dbenediktson] [~vishk] [~hanm] [~eribeiro] thank you all for working on a patch and reviewing.
I'm a bit confused about the state of this issue. The initial patch by Vishal proposed to
check if the host is reachable in {{StaticHostProvider.resolveAndShuffle}}. That is supposed
to avoid servers that are down at the time we execute {{resolveAndShuffle}}.

Unless I'm missing something, the latest patch does not seem to be addressing the issue described
here. It doesn't reduce the delay to connect to some server. Instead, it sets a lower bound
for the connection timeout.

I don't think the approach of testing that server is reachable is bad because we don't have
to do it often, only in the beginning and as we hit unavailable servers. We also need to be
careful to not exclude unavailable servers permanently from the list of servers, you might
and will probably come back eventually.

> 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: Dan Benediktson
>             Fix For: 3.5.3, 3.6.0
>
>         Attachments: ZOOKEEPER-2447-MinConnectTimeoutOnly.patch, 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}



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message