I will answer my own question. It turns out the zookeeper addresses in server.properties are wrong. But it is not easy to tell from the error message.
Regards, Libo From: Yu, Libo [ICG-IT] Sent: Thursday, May 23, 2013 10:48 AM To: 'users@kafka.apache.org' Subject: Failed to launch 0.8 stable server Hi, After the zookeepers were up, when I tired to launch kafka server, I got this error: [2013-05-23 10:45:24,072] FATAL Fatal error during KafkaServerStable startup. Prepare to shutdown (kafka.server.KafkaServerStartable) java.lang.RuntimeException: A broker is already registered on the path /brokers/ids/1. This probably indicates that you either have configured a brokerid that is already in use, or else you have shutdown this broker and restarted it faster than the zookeeper timeout so it appears to be re-registering. at kafka.utils.ZkUtils$.registerBrokerInZk(ZkUtils.scala:194) at kafka.server.KafkaZooKeeper.kafka$server$KafkaZooKeeper$$registerBrokerInZk(KafkaZooKeeper.scala:51) at kafka.server.KafkaZooKeeper.startup(KafkaZooKeeper.scala:41) at kafka.server.KafkaServer.startup(KafkaServer.scala:78) at kafka.server.KafkaServerStartable.startup(KafkaServerStartable.scala:34) at kafka.Kafka$.main(Kafka.scala:46) at kafka.Kafka.main(Kafka.scala) [2013-05-23 10:45:24,074] INFO [Kafka Server 1], shutting down (kafka.server.KafkaServer) [2013-05-23 10:45:24,076] INFO Closing zookeeper client... (kafka.server.KafkaZooKeeper) [2013-05-23 10:45:24,077] INFO Terminate ZkClient event thread. (org.I0Itec.zkcl Everything is freshly installed. It is so frustrating. Regards, Libo