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https://issues.apache.org/jira/browse/SPARK-17535?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen resolved SPARK-17535.
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Resolution: Won't Fix
I don't think volatile matters here. It's not the point I was making actually;
it was about the fact that this makes it possible to make this code
un-thread-safe later if you happened to do extra init after the reference was
set. It's not worth the complexity if there's no problem.a
> Performance Improvement of Signleton pattern in SparkContext
> ------------------------------------------------------------
>
> Key: SPARK-17535
> URL: https://issues.apache.org/jira/browse/SPARK-17535
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 2.0.0
> Reporter: Jianfei Wang
> Labels: easyfix, performance
>
> I think the singleton pattern of SparkContext is inefficient if there are
> many request to get the SparkContext,
> So we can write the singleton pattern as below,The second way if more
> efficient when there are many request to get the SparkContext.
> {code}
> // the current version
> def getOrCreate(): SparkContext = {
> SPARK_CONTEXT_CONSTRUCTOR_LOCK.synchronized {
> if (activeContext.get() == null) {
> setActiveContext(new SparkContext(), allowMultipleContexts = false)
> }
> activeContext.get()
> }
> }
> // by myself
> def getOrCreate(): SparkContext = {
> if (activeContext.get() == null) {
> SPARK_CONTEXT_CONSTRUCTOR_LOCK.synchronized {
> if(activeContext.get == null) {
> @volatile val sparkContext = new SparkContext()
> setActiveContext(sparkContext, allowMultipleContexts = false)
> }
> }
> activeContext.get()
> }
> }
> {code}
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