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https://issues.apache.org/jira/browse/KAFKA-597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527168#comment-13527168
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Jay Kreps commented on KAFKA-597:
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Nice catch on the brace, will fix before check in.
With respect to the scaladoc, that is a legitimate call, I think. The api take
default values so all of the following should work:
scheduler.schedule("task", println("hello")) // immediately kick of a
one-time background task
scheduler.schedule("task", println("hello"), delay=50) // kick off a one-time
task in 50ms
scheduler.schedule("task", println("hello"), period = 50) // immediately kick
off a repeating task that will repeat every 50 ms
etc
WRT daemon, you are correct, but I don't think this is necessarily a bad thing.
The requirement of the api is that you call startup() before calling schedule()
and call shutdown() when done. Shutdown was previously a non-blocking call so
it was very important whether the threads were blocking or non-blocking (but
this functionality was totally *broken*) because you would likely call
shutdown() and then exit the JVM. Now the only possible way to get to JVM
shutdown with remaining scheduler threads is if your program has a bug and
fails to call shutdown(). What should we do in this case? Hard to say. All
tasks must handle unclean shutdown because unclean shutdown is a lot like a
crash. Blocking JVM shutdown can really mess up automated deployment, so
defaulting to that is not necessarily wise. So I am fine with either default
but at least the consumer scheduler really needs to be set to daemon so we
don't block people's jvms.
> Refactor KafkaScheduler
> -----------------------
>
> Key: KAFKA-597
> URL: https://issues.apache.org/jira/browse/KAFKA-597
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 0.8.1
> Reporter: Jay Kreps
> Priority: Minor
> Attachments: KAFKA-597-v1.patch, KAFKA-597-v2.patch,
> KAFKA-597-v3.patch, KAFKA-597-v4.patch, KAFKA-597-v5.patch
>
>
> It would be nice to cleanup KafkaScheduler. Here is what I am thinking
> Extract the following interface:
> trait Scheduler {
> def startup()
> def schedule(fun: () => Unit, name: String, delayMs: Long = 0, periodMs:
> Long): Scheduled
> def shutdown(interrupt: Boolean = false)
> }
> class Scheduled {
> def lastExecution: Long
> def cancel()
> }
> We would have two implementations, KafkaScheduler and MockScheduler.
> KafkaScheduler would be a wrapper for ScheduledThreadPoolExecutor.
> MockScheduler would only allow manual time advancement rather than using the
> system clock, we would switch unit tests over to this.
> This change would be different from the existing scheduler in a the following
> ways:
> 1. Would not return a ScheduledFuture (since this is useless)
> 2. shutdown() would be a blocking call. The current shutdown calls, don't
> really do what people want.
> 3. We would remove the daemon thread flag, as I don't think it works.
> 4. It returns an object which let's you cancel the job or get the last
> execution time.
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