[SPARK-6470] [YARN] Add support for YARN node labels.

This is difficult to write a test for because it relies on the latest version of YARN, but I verified manually that the patch does pass along the label expression on this version and containers are successfully launched.

Author: Sandy Ryza <sandy@cloudera.com>

Closes #5242 from sryza/sandy-spark-6470 and squashes the following commits:

6af87b9 [Sandy Ryza] Change info to warning
6e22d99 [Sandy Ryza] [YARN] SPARK-6470.  Add support for YARN node labels.

1 files changed, 30 insertions, 1 deletions

diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocator.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocator.scala
index 88d68d5556..8a08f561a2 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocator.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnAllocator.scala
@@ -117,6 +117,24 @@ private[yarn] class YarnAllocator(
   // For testing
   private val launchContainers = sparkConf.getBoolean("spark.yarn.launchContainers", true)
 
+  private val labelExpression = sparkConf.getOption("spark.yarn.executor.nodeLabelExpression")
+
+  // ContainerRequest constructor that can take a node label expression. We grab it through
+  // reflection because it's only available in later versions of YARN.
+  private val nodeLabelConstructor = labelExpression.flatMap { expr =>
+    try {
+      Some(classOf[ContainerRequest].getConstructor(classOf[Resource],
+        classOf[Array[String]], classOf[Array[String]], classOf[Priority], classOf[Boolean],
+        classOf[String]))
+    } catch {
+      case e: NoSuchMethodException => {
+        logWarning(s"Node label expression $expr will be ignored because YARN version on" +
+          " classpath does not support it.")
+        None
+      }
+    }
+  }
+
   def getNumExecutorsRunning: Int = numExecutorsRunning
 
   def getNumExecutorsFailed: Int = numExecutorsFailed
@@ -211,7 +229,7 @@ private[yarn] class YarnAllocator(
         s"cores and ${resource.getMemory} MB memory including $memoryOverhead MB overhead")
 
       for (i <- 0 until missing) {
-        val request = new ContainerRequest(resource, null, null, RM_REQUEST_PRIORITY)
+        val request = createContainerRequest(resource)
         amClient.addContainerRequest(request)
         val nodes = request.getNodes
         val hostStr = if (nodes == null || nodes.isEmpty) "Any" else nodes.last
@@ -231,6 +249,17 @@ private[yarn] class YarnAllocator(
   }
 
   /**
+   * Creates a container request, handling the reflection required to use YARN features that were
+   * added in recent versions.
+   */
+  private def createContainerRequest(resource: Resource): ContainerRequest = {
+    nodeLabelConstructor.map { constructor =>
+      constructor.newInstance(resource, null, null, RM_REQUEST_PRIORITY, true: java.lang.Boolean,
+        labelExpression.orNull)
+    }.getOrElse(new ContainerRequest(resource, null, null, RM_REQUEST_PRIORITY))
+  }
+
+  /**
    * Handle containers granted by the RM by launching executors on them.
    *
    * Due to the way the YARN allocation protocol works, certain healthy race conditions can result