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https://issues.apache.org/jira/browse/SPARK-35722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17361501#comment-17361501
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Apache Spark commented on SPARK-35722:
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User 'yikf' has created a pull request for this issue:
https://github.com/apache/spark/pull/32877
> wait until something does get queued
> ------------------------------------
>
> Key: SPARK-35722
> URL: https://issues.apache.org/jira/browse/SPARK-35722
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 3.0.0
> Reporter: yikf
> Priority: Minor
> Fix For: 3.2.0
>
>
> If nothing has been added to the queue, should wait until something does get
> queued instead of loop after timeout, It prevents an ineffective loop.
>
> Currently, We will cotinue loop after timeout of the 100ms if the queue is
> empty, It prevents an ineffective cycle.
> eg:
> 1. referenceQueue.remove(timeout), if the queue is empty
> 2. remove will return directly after wait timeout
> 3. continue the loop.
> reference
> # Spark ContextCleaner
> {code:java}
> while (!stopped) {
> try {
> val reference =
> Option(referenceQueue.remove(ContextCleaner.REF_QUEUE_POLL_TIMEOUT))
> .map(_.asInstanceOf[CleanupTaskWeakReference])
> ...
> }
> ...
> }{code}
> 2. JDK ReferenceQueue
> {code:java}
> public Reference<? extends T> remove(long timeout)
> throws IllegalArgumentException, InterruptedException
> {
> if (timeout < 0) {
> throw new IllegalArgumentException("Negative timeout value");
> }
> synchronized (lock) {
> Reference<? extends T> r = reallyPoll();
> if (r != null) return r;
> long start = (timeout == 0) ? 0 : System.nanoTime();
> for (;;) {
> lock.wait(timeout);
> r = reallyPoll();
> if (r != null) return r;
> if (timeout != 0) {
> long end = System.nanoTime();
> timeout -= (end - start) / 1000_000;
> if (timeout <= 0) return null;
> start = end;
> }
> }
> }
> }
> {code}
> If we have not timeout, Thread will wait until Reference.enqueue be called.
> i.e. something that need to be cleanUp be add to the queue.
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