Merge pull request #937 from jerryshao/localProperties-fix

Fix PR926 local properties issues in Spark Streaming like scenarios

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -256,7 +256,9 @@ class SparkContext(
   private[spark] var checkpointDir: Option[String] = None
 
   // Thread Local variable that can be used by users to pass information down the stack
-  private val localProperties = new ThreadLocal[Properties]
+  private val localProperties = new InheritableThreadLocal[Properties] {
+    override protected def childValue(parent: Properties): Properties = new Properties(parent)
+  }
 
   def initLocalProperties() {
     localProperties.set(new Properties())
@@ -273,6 +275,9 @@ class SparkContext(
     }
   }
 
+  def getLocalProperty(key: String): String =
+    Option(localProperties.get).map(_.getProperty(key)).getOrElse(null)
+
   /** Set a human readable description of the current job. */
   def setJobDescription(value: String) {
     setLocalProperty(SparkContext.SPARK_JOB_DESCRIPTION, value)

core/src/test/scala/org/apache/spark/ThreadingSuite.scala

@@ -40,7 +40,7 @@ object ThreadingSuiteState {
 }
 
 class ThreadingSuite extends FunSuite with LocalSparkContext {
-  
+
   test("accessing SparkContext form a different thread") {
     sc = new SparkContext("local", "test")
     val nums = sc.parallelize(1 to 10, 2)
@@ -149,4 +149,47 @@ class ThreadingSuite extends FunSuite with LocalSparkContext {
       fail("One or more threads didn't see runningThreads = 4")
     }
   }
+
+  test("set local properties in different thread") {
+    sc = new SparkContext("local", "test")
+    val sem = new Semaphore(0)
+
+    val threads = (1 to 5).map { i =>
+      new Thread() {
+        override def run() {
+          sc.setLocalProperty("test", i.toString)
+          assert(sc.getLocalProperty("test") === i.toString)
+          sem.release()
+        }
+      }
+    }
+
+    threads.foreach(_.start())
+
+    sem.acquire(5)
+    assert(sc.getLocalProperty("test") === null)
+  }
+
+  test("set and get local properties in parent-children thread") {
+    sc = new SparkContext("local", "test")
+    sc.setLocalProperty("test", "parent")
+    val sem = new Semaphore(0)
+
+    val threads = (1 to 5).map { i =>
+      new Thread() {
+        override def run() {
+          assert(sc.getLocalProperty("test") === "parent")
+          sc.setLocalProperty("test", i.toString)
+          assert(sc.getLocalProperty("test") === i.toString)
+          sem.release()
+        }
+      }
+    }
+
+    threads.foreach(_.start())
+
+    sem.acquire(5)
+    assert(sc.getLocalProperty("test") === "parent")
+    assert(sc.getLocalProperty("Foo") === null)
+  }
 }