[ZOOKEEPER-2447] Zookeeper adds good delay when one of the quorum host is not reachable

• Type: Bug
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.4.9
• Fix Version/s: 3.4.9
• Assignee: Vishal Khandelwal
• Reporter: Vishal Khandelwal
• Created: 15/Jun/16 12:56
• Updated: 11/Nov/16 07:30

Description

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

 @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();    
  }

Following fix can be added to StaticHostProvider.resolveAndShuffle

 if(taddr.isReachable(4000 // can be some value)) {
                      tmpList.add(new InetSocketAddress(taddr, address.getPort()));
                    } 

Issue Links

• relates to: ZOOKEEPER-2449 Refresh the invalid host which got unknownhostexception during connection in StaticHostProvider