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From "chendihao (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-10283) Client can't connect with all the running zk servers in MiniZooKeeperCluster
Date Mon, 06 Jan 2014 04:03:50 GMT
chendihao created HBASE-10283:
---------------------------------

             Summary: Client can't connect with all the running zk servers in MiniZooKeeperCluster
                 Key: HBASE-10283
                 URL: https://issues.apache.org/jira/browse/HBASE-10283
             Project: HBase
          Issue Type: Bug
    Affects Versions: 0.94.3
            Reporter: chendihao


Refer to HBASE-3052, multiple zk servers can run together in minicluster. The problem is that
client can only connect with the first zk server and if you kill the first one, it fails to
access the cluster even though other zk servers are serving.

It's easy to repro.  Firstly `TEST_UTIL.startMiniZKCluster(3)`. Secondly call `killCurrentActiveZooKeeperServer`
in MiniZooKeeperCluster. Then when you construct the zk client, it can't connect with the
zk cluster for any way. Here is the simple log you can refer.
{noformat}
2014-01-03 12:06:58,625 INFO  [main] zookeeper.MiniZooKeeperCluster(194): Started MiniZK Cluster
and connect 1 ZK server on client port: 55227
......
2014-01-03 12:06:59,134 INFO  [main] zookeeper.MiniZooKeeperCluster(264): Kill the current
active ZK servers in the cluster on client port: 55227
2014-01-03 12:06:59,134 INFO  [main] zookeeper.MiniZooKeeperCluster(272): Activate a backup
zk server in the cluster on client port: 55228
2014-01-03 12:06:59,366 INFO  [main-EventThread] zookeeper.ZooKeeper(434): Initiating client
connection, connectString=localhost:55227 sessionTimeout=3000 watcher=com.xiaomi.infra.timestamp.TimestampWatcher@a383118
{noformat}

The log is kind of problematic because it always show "Started MiniZK Cluster and connect
1 ZK server" but actually there're three zk servers.

Looking deeply we find that the client is still trying to connect with the dead zk server's
port. When I print out the zkQuorum it used, only the first zk server's hostport is there
and it will not change no matter you kill the server or not. The reason for this is in ZKConfig
which will convert HBase settings into zk's. MiniZooKeeperCluster create three servers with
the same host name, "localhost", and different ports. But HBase self use the port and ZKConfig
will ignore the other two servers which have the same host name.

MiniZooKeeperCluster works improperly before we fix this. The bug is not found because we
never test whether HBase works or not if we kill the zk active or backup servers in ut. But
apparently we should. 



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