[jira] [Commented] (SPARK-7624) Task scheduler delay is increasing time over time in spark local mode

["Sean Owen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-7624?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14543325#comment-14543325 ] 

Sean Owen commented on SPARK-7624:
----------------------------------

[~davies] thoughts on the impact of those few lines?

> Task scheduler delay is increasing time over time in spark local mode
> ---------------------------------------------------------------------
>
>                 Key: SPARK-7624
>                 URL: https://issues.apache.org/jira/browse/SPARK-7624
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>    Affects Versions: 1.3.1
>            Reporter: Jack Hu
>              Labels: delay, schedule
>
> I am running a simple spark streaming program with spark 1.3.1 in local mode, it receives json string from a socket with rate 50 events per second, it can run well in first 6 hours (although the minor gc count per minute is increasing all the time), after that, i can see that the scheduler delay in every task is significant increased from 10 ms to 100 ms, after 10 hours running, the task delay is about 800 ms and cpu is also increased from 2% to 30%. This causes the steaming job can not finish in one batch interval (5 seconds). I dumped the java memory after 16 hours and can see there are about 200000 {{org.apache.spark.scheduler.local.ReviveOffers}} objects in {{akka.actor.LightArrayRevolverScheduler$TaskQueue[]}}. Then i checked the code and see only one place may put the {{ReviveOffers}} to akka {{LightArrayRevolverScheduler}}: the {{LocalActor::reviveOffers}}
> {code}
>  def reviveOffers() {
>     val offers = Seq(new WorkerOffer(localExecutorId, localExecutorHostname, freeCores))
>     val tasks = scheduler.resourceOffers(offers).flatten
>     for (task <- tasks) {
>       freeCores -= scheduler.CPUS_PER_TASK
>       executor.launchTask(executorBackend, taskId = task.taskId, attemptNumber = task.attemptNumber,
>         task.name, task.serializedTask)
>     }
>     if (tasks.isEmpty && scheduler.activeTaskSets.nonEmpty) {
>       // Try to reviveOffer after 1 second, because scheduler may wait for locality timeout
>       context.system.scheduler.scheduleOnce(1000 millis, self, ReviveOffers)
>     }
> }
> {code}
> I removed the last three lines in this method (the whole {{if}} block, which is introduced from https://issues.apache.org/jira/browse/SPARK-4939), it worked smooth after 20 hours running, the scheduler delay is about 10 ms all the time. So there should have some conditions that the ReviveOffers will be duplicate scheduled? I am not sure why this happens, but i feel that this is the root cause of this issue. 
> My spark settings:
> #  Memor: 3G
> # CPU: 8 cores 
> # Streaming Batch interval: 5 seconds.  
> Here are my streaming code:
> {code}
> val input = ssc.socketTextStream(
>       hostname, port, StorageLevel.MEMORY_ONLY_SER).mapPartitions(
>       /// parse the json to Order
>       Order(_), preservePartitioning = true)
> val mresult = input.map(
>       v => (v.customer, UserSpending(v.customer, v.count * v.price, v.timestamp.toLong))).cache()
> val tempr  = mresult.window(
>             Seconds(firstStageWindowSize), 
>             Seconds(firstStageWindowSize)
>           ).transform(
>             rdd => rdd.union(rdd).union(rdd).union(rdd)
>           )
> tempr.count.print
> tempr.cache().foreachRDD((rdd, t) => {
>             for (i <- 1 to 5) {
>               val c = rdd.filter(x=>scala.util.Random.nextInt(5) == i).count()
>               println("""T: """ + t + """: """ + c)
>             }
>           })
> {code}



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