Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/8909#discussion_r42817021
--- 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 --
Yeah agreed. In fact @volatile should never be needed on a val.
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