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From "Jason Rosenberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-589) Clean shutdown after startup connection failure
Date Mon, 05 Nov 2012 20:34:12 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13490899#comment-13490899

Jason Rosenberg commented on KAFKA-589:

I was using KafkaServerStartable.startup(), but switched to KafkaServer.startup(), because
I wanted to have a bit more control of things, e.g. I want to be able know if there was a
problem within the container, and retry, etc.  In KafkaServerStartable.startup(), if there's
an exception, it swallows the exception, and then calls shutdown(), but the caller has no
idea if the startup was successful or not.

But I don't think that's relevant here.  I think it's counter intuitive that the KafkaServer.startup()
would fail to startup, and throw an exception, and then not cleanup after itself, and require
a call to shutdown in the first place.
> Clean shutdown after startup connection failure
> -----------------------------------------------
>                 Key: KAFKA-589
>                 URL: https://issues.apache.org/jira/browse/KAFKA-589
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 0.8, 0.7.2
>            Reporter: Jason Rosenberg
>            Assignee: Swapnil Ghike
>            Priority: Minor
>              Labels: bugs, newbie
> Hi,
> 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
> 	at org.I0Itec.zkclient.ZkClient.connect(ZkClient.java:876)
> 	at org.I0Itec.zkclient.ZkClient.<init>(ZkClient.java:98)
> 	at org.I0Itec.zkclient.ZkClient.<init>(ZkClient.java:84)
> 	at kafka.server.KafkaZooKeeper.startup(KafkaZooKeeper.scala:44)
> 	at kafka.log.LogManager.<init>(LogManager.scala:93)
> 	at kafka.server.KafkaServer.startup(KafkaServer.scala:58)
>         ....
>         ....
> 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$ConditionObject)
> 	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:196)
> 	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2025)
> 	at java.util.concurrent.DelayQueue.take(DelayQueue.java:164)
> 	at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:609)
> 	at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:602)
> 	at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:947)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
> 	at java.lang.Thread.run(Thread.java:680)
> 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()....

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