I'm embedding the kafka server (0.7.2) in an application container. I've noticed that if I try to start the server without zookeeper being available, by default it gets a zk connection timeout after 6 seconds, and then throws an Exception out of KafkaServer.startup()....E.g., I see this stack trace:
Exception in thread "main" org.I0Itec.zkclient.exception.ZkTimeoutException: Unable to connect to zookeeper server within timeout: 6000
So that's ok, I can catch the exception, and then shut everything down gracefully, in this case. However, when I do this, it seems there is a daemon thread still around, which doesn't quit, and so the server never actually exits the jvm. Specifically, this thread seems to hang around:
"kafka-logcleaner-0" prio=5 tid=7fd9b48b1000 nid=0x112c08000 waiting on condition [112c07000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <7f40d4be8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
Looking at the code in kafka.log.LogManager(), it does seem like it starts up the scheduler to clean logs, before then trying to connect to zk (and in this case fail):
/* Schedule the cleanup task to delete old logs */
if(scheduler != null)
info("starting log cleaner every " + logCleanupIntervalMs + " ms")
scheduler.scheduleWithRate(cleanupLogs, 60 * 1000, logCleanupIntervalMs)
So this scheduler does not appear to be stopped if startup fails. However, if I catch the above RuntimeException, and then call KafkaServer.shutdown(), then it will stop the scheduler, and all is good.
However, it seems odd that if I get an exception when calling KafkaServer.startup(), that I should still have to do a KafkaServer.shutdown(). Rather, wouldn't it be better to have it internally cleanup after itself if startup() gets an exception? I'm not sure I can reliably call shutdown() after a failed startup()....