hi something about s4 benchmark

[baojian Zhou]

i start test the s4 benchmark application, and then run the ./bench-cluster.sh command then i got this error :

 21:23:18.570 [main] INFO  org.apache.s4.tools.ZKServer - Zookeeper server started on port [2181]

21:23:18.618 [main] INFO  org.apache.s4.tools.ZKServer - Defined S4 cluster [testCluster1] with [0] tasks with first listening port [12000]

21:23:18.706 [main] ERROR org.apache.s4.tools.ZKServer - Cannot initialize zookeeper with specified configuration

org.I0Itec.zkclient.exception.ZkNodeExistsException: org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists for /s4/clusters/testCluster2/tasks/Task-0

        at org.I0Itec.zkclient.exception.ZkException.create(ZkException.java:55) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient.retryUntilConnected(ZkClient.java:685) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient.create(ZkClient.java:304) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient.createPersistent(ZkClient.java:243) ~[zkclient-0.1.jar:na]

        at org.apache.s4.comm.tools.TaskSetup.setup(TaskSetup.java:69) ~[s4-comm-0.6.0-incubating.jar:0.6.0-incubating]

        at org.apache.s4.tools.ZKServer.main(ZKServer.java:94) ~[s4-tools-0.6.0-incubating.jar:0.6.0-incubating]

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.6.0_20]

        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.6.0_20]

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.6.0_20]

        at java.lang.reflect.Method.invoke(Method.java:616) ~[na:1.6.0_20]

        at org.apache.s4.tools.Tools$Task.dispatch(Tools.java:57) [s4-tools-0.6.0-incubating.jar:0.6.0-incubating]

        at org.apache.s4.tools.Tools.main(Tools.java:97) [s4-tools-0.6.0-incubating.jar:0.6.0-incubating]

Caused by: org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists for /s4/clusters/testCluster2/tasks/Task-0

        at org.apache.zookeeper.KeeperException.create(KeeperException.java:110) ~[zookeeper-3.3.3.jar:3.3.3-1073969]

        at org.apache.zookeeper.KeeperException.create(KeeperException.java:42) ~[zookeeper-3.3.3.jar:3.3.3-1073969]

        at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:637) ~[zookeeper-3.3.3.jar:3.3.3-1073969]

        at org.I0Itec.zkclient.ZkConnection.create(ZkConnection.java:87) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient$1.call(ZkClient.java:308) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient$1.call(ZkClient.java:304) ~[zkclient-0.1.jar:na]

        at org.I0Itec.zkclient.ZkClient.retryUntilConnected(ZkClient.java:675) ~[zkclient-0.1.jar:na]

        ... 10 common frames omitted

can anyone tell me why?