YARN-7181. CPUTimeTracker.updateElapsedJiffies can report negative usage. (Miklos Szegedi via Haibo Chen)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/CpuTimeTracker.java

@@ -97,7 +97,9 @@ public class CpuTimeTracker {
    * @param newTime new sample time
    */
   public void updateElapsedJiffies(BigInteger elapsedJiffies, long newTime) {
-    cumulativeCpuTime = elapsedJiffies.multiply(jiffyLengthInMillis);
+    BigInteger newValue = elapsedJiffies.multiply(jiffyLengthInMillis);
+    cumulativeCpuTime = newValue.compareTo(cumulativeCpuTime) >= 0 ?
+        newValue : cumulativeCpuTime;
     sampleTime = newTime;
   }
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestCpuTimeTracker.java

@@ -0,0 +1,52 @@
+/**
+ * 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.util;
+
+import org.junit.Test;
+import java.math.BigInteger;
+import static org.junit.Assert.assertTrue;
+
+public class TestCpuTimeTracker {
+  @Test
+  public void test() throws InterruptedException {
+    CpuTimeTracker tracker = new CpuTimeTracker(10);
+    tracker.updateElapsedJiffies(
+        BigInteger.valueOf(100),
+        System.currentTimeMillis());
+    float val1 = tracker.getCpuTrackerUsagePercent();
+    assertTrue(
+        "Not invalid CPU usage",
+        val1 == -1.0);
+    Thread.sleep(1000);
+    tracker.updateElapsedJiffies(
+        BigInteger.valueOf(200),
+        System.currentTimeMillis());
+    float val2 = tracker.getCpuTrackerUsagePercent();
+    assertTrue(
+        "Not positive CPU usage",
+        val2 > 0);
+    Thread.sleep(1000);
+    tracker.updateElapsedJiffies(
+        BigInteger.valueOf(0),
+        System.currentTimeMillis());
+    float val3 = tracker.getCpuTrackerUsagePercent();
+    assertTrue(
+        "Not positive CPU usage",
+        val3 == 0.0);
+  }
+}