Github user tedyu commented on a diff in the pull request: https://github.com/apache/spark/pull/8909#discussion_r42816849 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala --- @@ -1196,46 +1174,90 @@ class SQLContext(@transient val sparkContext: SparkContext) // Register a succesfully instantiatd context to the singleton. This should be at the end of // the class definition so that the singleton is updated only if there is no exception in the // construction of the instance. - SQLContext.setLastInstantiatedContext(self) + sparkContext.addSparkListener(new SparkListener { + override def onApplicationEnd(applicationEnd: SparkListenerApplicationEnd): Unit = { + SQLContext.clearInstantiatedContext(self) + } + }) + + SQLContext.setInstantiatedContext(self) } /** * This SQLContext object contains utility functions to create a singleton SQLContext instance, - * or to get the last created SQLContext instance. + * or to get the created SQLContext instance. + * + * It also provides utility functions to support preference for threads in multiple sessions + * scenario, setActive could set a SQLContext for current thread, which will be returned by + * getOrCreate instead of the global one. */ object SQLContext { - private val INSTANTIATION_LOCK = new Object() + /** + * The active SQLContext for the current thread. + */ + private val activeContext: InheritableThreadLocal[SQLContext] = + new InheritableThreadLocal[SQLContext] /** - * Reference to the last created SQLContext. + * Reference to the created SQLContext. */ - @transient private val lastInstantiatedContext = new AtomicReference[SQLContext]() + @transient private val instantiatedContext = new AtomicReference[SQLContext]() --- End diff -- Should this be annotated @volatile ?
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