YARN-6870. Fix floating point inaccuracies in resource availability check in AllocationBasedResourceUtilizationTracker. (Brook Zhou via asuresh)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/scheduler/AllocationBasedResourceUtilizationTracker.java

@@ -118,19 +118,40 @@ public class AllocationBasedResourceUtilizationTracker implements
       return false;
     }
 
-    float vCores = (float) cpuVcores /
-        getContainersMonitor().getVCoresAllocatedForContainers();
     if (LOG.isDebugEnabled()) {
       LOG.debug("before cpuCheck [asked={} > allowed={}]",
-          this.containersAllocation.getCPU(), vCores);
+          this.containersAllocation.getCPU(),
+          getContainersMonitor().getVCoresAllocatedForContainers());
     }
-    // Check CPU.
-    if (this.containersAllocation.getCPU() + vCores > 1.0f) {
+    // Check CPU. Compare using integral values of cores to avoid decimal
+    // inaccuracies.
+    if (!hasEnoughCpu(this.containersAllocation.getCPU(),
+        getContainersMonitor().getVCoresAllocatedForContainers(), cpuVcores)) {
       return false;
     }
     return true;
   }
 
+  /**
+   * Returns whether there is enough space for coresRequested in totalCores.
+   * Converts currentAllocation usage to nearest integer count before comparing,
+   * as floats are inherently imprecise. NOTE: this calculation assumes that
+   * requested core counts must be integers, and currentAllocation core count
+   * must also be an integer.
+   *
+   * @param currentAllocation The current allocation, a float value from 0 to 1.
+   * @param totalCores The total cores in the system.
+   * @param coresRequested The number of cores requested.
+   * @return True if currentAllocationtotalCores*coresRequested <=
+   *         totalCores.
+   */
+  public boolean hasEnoughCpu(float currentAllocation, long totalCores,
+      int coresRequested) {
+    // Must not cast here, as it would truncate the decimal digits.
+    return Math.round(currentAllocation * totalCores)
+        + coresRequested <= totalCores;
+  }
+
   public ContainersMonitor getContainersMonitor() {
     return this.scheduler.getContainersMonitor();
   }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/scheduler/ContainerScheduler.java

@@ -392,7 +392,10 @@ public class ContainerScheduler extends AbstractService implements
       ResourceUtilization resourcesToFreeUp) {
     return resourcesToFreeUp.getPhysicalMemory() <= 0 &&
         resourcesToFreeUp.getVirtualMemory() <= 0 &&
-        resourcesToFreeUp.getCPU() <= 0.0f;
+        // Convert the number of cores to nearest integral number, due to
+        // imprecision of direct float comparison.
+        Math.round(resourcesToFreeUp.getCPU()
+            * getContainersMonitor().getVCoresAllocatedForContainers()) <= 0;
   }
 
   private ResourceUtilization resourcesToFreeUp(

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/scheduler/TestAllocationBasedResourceUtilizationTracker.java

@@ -0,0 +1,93 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.yarn.server.nodemanager.containermanager.scheduler;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import org.apache.hadoop.yarn.api.records.Resource;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+import org.apache.hadoop.yarn.event.AsyncDispatcher;
+import org.apache.hadoop.yarn.server.nodemanager.ContainerExecutor;
+import org.apache.hadoop.yarn.server.nodemanager.Context;
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.Container;
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainersMonitor;
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainersMonitorImpl;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Tests for the {@link AllocationBasedResourceUtilizationTracker} class.
+ */
+public class TestAllocationBasedResourceUtilizationTracker {
+
+  private ContainerScheduler mockContainerScheduler;
+
+  @Before
+  public void setup() {
+    mockContainerScheduler = mock(ContainerScheduler.class);
+    ContainersMonitor containersMonitor =
+        new ContainersMonitorImpl(mock(ContainerExecutor.class),
+            mock(AsyncDispatcher.class), mock(Context.class));
+    YarnConfiguration conf = new YarnConfiguration();
+    conf.setInt(YarnConfiguration.NM_PMEM_MB, 1024);
+    conf.setBoolean(YarnConfiguration.NM_PMEM_CHECK_ENABLED, true);
+    conf.setBoolean(YarnConfiguration.NM_VMEM_CHECK_ENABLED, true);
+    conf.setFloat(YarnConfiguration.NM_VMEM_PMEM_RATIO, 2.0f);
+    conf.setInt(YarnConfiguration.NM_VCORES, 8);
+    containersMonitor.init(conf);
+    when(mockContainerScheduler.getContainersMonitor())
+        .thenReturn(containersMonitor);
+  }
+
+  /**
+   * Node has capacity for 1024 MB and 8 cores. Saturate the node. When full the
+   * hasResourceAvailable should return false.
+   */
+  @Test
+  public void testHasResourcesAvailable() {
+    AllocationBasedResourceUtilizationTracker tracker =
+        new AllocationBasedResourceUtilizationTracker(mockContainerScheduler);
+    Container testContainer = mock(Container.class);
+    when(testContainer.getResource()).thenReturn(Resource.newInstance(512, 4));
+    for (int i = 0; i < 2; i++) {
+      Assert.assertTrue(tracker.hasResourcesAvailable(testContainer));
+      tracker.addContainerResources(testContainer);
+    }
+    Assert.assertFalse(tracker.hasResourcesAvailable(testContainer));
+  }
+
+  /**
+   * Test the case where the current allocation has been truncated to 0.8888891
+   * (8/9 cores used). Request 1 additional core - hasEnoughCpu should return
+   * true.
+   */
+  @Test
+  public void testHasEnoughCpu() {
+    AllocationBasedResourceUtilizationTracker tracker =
+        new AllocationBasedResourceUtilizationTracker(mockContainerScheduler);
+    float currentAllocation = 0.8888891f;
+    long totalCores = 9;
+    int alreadyUsedCores = 8;
+    Assert.assertTrue(tracker.hasEnoughCpu(currentAllocation, totalCores,
+        (int) totalCores - alreadyUsedCores));
+    Assert.assertFalse(tracker.hasEnoughCpu(currentAllocation, totalCores,
+        (int) totalCores - alreadyUsedCores + 1));
+  }
+}