YARN-2539. FairScheduler: Set the default value for maxAMShare to 0.5. (Wei Yan via kasha)

(cherry picked from commit 43efdd30b5)

hadoop-yarn-project/CHANGES.txt

@@ -211,6 +211,9 @@ Release 2.6.0 - UNRELEASED
     YARN-1372. Ensure all completed containers are reported to the AMs across
     RM restart. (Anubhav Dhoot via jianhe)
 
+    YARN-2539. FairScheduler: Set the default value for maxAMShare to 0.5. 
+    (Wei Yan via kasha)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationConfiguration.java

@@ -130,7 +130,7 @@ public AllocationConfiguration(Configuration conf) {
     queueMaxAMShares = new HashMap<String, Float>();
     userMaxAppsDefault = Integer.MAX_VALUE;
     queueMaxAppsDefault = Integer.MAX_VALUE;
-    queueMaxAMShareDefault = -1.0f;
+    queueMaxAMShareDefault = 0.5f;
     queueAcls = new HashMap<String, Map<QueueACL, AccessControlList>>();
     minSharePreemptionTimeouts = new HashMap<String, Long>();
     fairSharePreemptionTimeouts = new HashMap<String, Long>();

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationFileLoaderService.java

@@ -224,7 +224,7 @@ public synchronized void reloadAllocations() throws IOException,
         new HashMap<String, Map<QueueACL, AccessControlList>>();
     int userMaxAppsDefault = Integer.MAX_VALUE;
     int queueMaxAppsDefault = Integer.MAX_VALUE;
-    float queueMaxAMShareDefault = -1.0f;
+    float queueMaxAMShareDefault = 0.5f;
     long defaultFairSharePreemptionTimeout = Long.MAX_VALUE;
     long defaultMinSharePreemptionTimeout = Long.MAX_VALUE;
     float defaultFairSharePreemptionThreshold = 0.5f;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestFairScheduler.java

@@ -3128,7 +3128,7 @@ public void testQueueMaxAMShareDefault() throws Exception {
     out.println("<queue name=\"queue1\">");
     out.println("</queue>");
     out.println("<queue name=\"queue2\">");
-    out.println("<maxAMShare>1.0</maxAMShare>");
+    out.println("<maxAMShare>0.4</maxAMShare>");
     out.println("</queue>");
     out.println("<queue name=\"queue3\">");
     out.println("</queue>");
@@ -3172,40 +3172,42 @@ public void testQueueMaxAMShareDefault() throws Exception {
     assertEquals("Queue queue5's fair share should be 0", 0, queue5
         .getFairShare().getMemory());
 
-    List<String> queues = Arrays.asList("root.default", "root.queue3",
+    List<String> queues = Arrays.asList("root.queue3", "root.queue4",
-        "root.queue4", "root.queue5");
+        "root.queue5");
     for (String queue : queues) {
       createSchedulingRequest(1 * 1024, queue, "user1");
       scheduler.update();
       scheduler.handle(updateEvent);
     }
 
-    Resource amResource1 = Resource.newInstance(2048, 1);
+    Resource amResource1 = Resource.newInstance(1024, 1);
     int amPriority = RMAppAttemptImpl.AM_CONTAINER_PRIORITY.getPriority();
 
-    // Exceeds queue limit, but default maxAMShare is -1.0 so it doesn't matter
+    // The fair share is 2048 MB, and the default maxAMShare is 0.5f,
+    // so the AM is accepted.
     ApplicationAttemptId attId1 = createAppAttemptId(1, 1);
     createApplicationWithAMResource(attId1, "queue1", "test1", amResource1);
-    createSchedulingRequestExistingApplication(2048, 1, amPriority, attId1);
+    createSchedulingRequestExistingApplication(1024, 1, amPriority, attId1);
     FSAppAttempt app1 = scheduler.getSchedulerApp(attId1);
     scheduler.update();
     scheduler.handle(updateEvent);
-    assertEquals("Application1's AM requests 2048 MB memory",
+    assertEquals("Application1's AM requests 1024 MB memory",
-        2048, app1.getAMResource().getMemory());
+        1024, app1.getAMResource().getMemory());
     assertEquals("Application1's AM should be running",
         1, app1.getLiveContainers().size());
-    assertEquals("Queue1's AM resource usage should be 2048 MB memory",
+    assertEquals("Queue1's AM resource usage should be 1024 MB memory",
-        2048, queue1.getAmResourceUsage().getMemory());
+        1024, queue1.getAmResourceUsage().getMemory());
 
-    // Exceeds queue limit, and maxAMShare is 1.0
+    // Now the fair share is 1639 MB, and the maxAMShare is 0.4f,
+    // so the AM is not accepted.
     ApplicationAttemptId attId2 = createAppAttemptId(2, 1);
     createApplicationWithAMResource(attId2, "queue2", "test1", amResource1);
-    createSchedulingRequestExistingApplication(2048, 1, amPriority, attId2);
+    createSchedulingRequestExistingApplication(1024, 1, amPriority, attId2);
     FSAppAttempt app2 = scheduler.getSchedulerApp(attId2);
     scheduler.update();
     scheduler.handle(updateEvent);
-    assertEquals("Application2's AM requests 2048 MB memory",
+    assertEquals("Application2's AM requests 1024 MB memory",
-        2048, app2.getAMResource().getMemory());
+        1024, app2.getAMResource().getMemory());
     assertEquals("Application2's AM should not be running",
         0, app2.getLiveContainers().size());
     assertEquals("Queue2's AM resource usage should be 0 MB memory",

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/apt/FairScheduler.apt.vm

@@ -246,8 +246,8 @@ Allocation file format
    * maxAMShare: limit the fraction of the queue's fair share that can be used
      to run application masters. This property can only be used for leaf queues.
      For example, if set to 1.0f, then AMs in the leaf queue can take up to 100%
-     of both the memory and CPU fair share. The default value is -1.0f, which
+     of both the memory and CPU fair share. The value of -1.0f will disable
-     means that this check is disabled.
+     this feature and the amShare will not be checked. The default value is 0.5f.
 
    * weight: to share the cluster non-proportionally with other queues. Weights
      default to 1, and a queue with weight 2 should receive approximately twice