Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/5907#discussion_r29834015
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala ---
@@ -607,8 +614,27 @@ class StreamingContext private[streaming] (
*/
object StreamingContext extends Logging {
+ /**
+ * Lock that guards access to global variables that track active
StreamingContext.
+ */
+ private val ACTIVATION_LOCK = new Object()
- private[streaming] val DEFAULT_CLEANER_TTL = 3600
+ private var activeContext: AtomicReference[StreamingContext] =
+ new AtomicReference[StreamingContext](null)
+
+ private def assertNoOtherContextIsActive(): Unit = {
+ ACTIVATION_LOCK.synchronized {
+ if (activeContext.get() != null) {
+ throw new SparkException("Only one StreamingContext may be started
in this JVM")
--- End diff --
Well, let me be a little bit more unambiguous in the choice of verbs. We
are allowed to instantiate multiple StreamingContexts provided only one is
started (`ssc.start()`) at a time. That's why I used "started" so that it
directly maps to `ssc.start()`. This is different from `SparkContexts` where it
is started as soon as it is instantiated.
I will add the callsite information.
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