HADOOP-13283. Support reset operation for new global storage statistics and per FS storage stats. Contributed by Mingliang Liu.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/EmptyStorageStatistics.java

@@ -29,15 +29,22 @@ class EmptyStorageStatistics extends StorageStatistics {
     super(name);
   }
 
+  @Override
   public Iterator<LongStatistic> getLongStatistics() {
     return Collections.emptyIterator();
   }
 
+  @Override
   public Long getLong(String key) {
     return null;
   }
 
+  @Override
   public boolean isTracked(String key) {
     return false;
   }
+
+  @Override
+  public void reset() {
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -3500,8 +3500,11 @@ public StorageStatistics provide() {
    * Reset all statistics for all file systems
    */
   public static synchronized void clearStatistics() {
-    for(Statistics stat: statisticsTable.values()) {
+    final Iterator<StorageStatistics> iterator =
-      stat.reset();
+        GlobalStorageStatistics.INSTANCE.iterator();
+    while (iterator.hasNext()) {
+      final StorageStatistics statistics = iterator.next();
+      statistics.reset();
     }
   }
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystemStorageStatistics.java

@@ -126,6 +126,7 @@ public Long getLong(String key) {
    *
    * @return         True only if the statistic is being tracked.
    */
+  @Override
   public boolean isTracked(String key) {
     for (String k: KEYS) {
       if (k.equals(key)) {
@@ -134,4 +135,9 @@ public boolean isTracked(String key) {
     }
     return false;
   }
+
+  @Override
+  public void reset() {
+    stats.reset();
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/GlobalStorageStatistics.java

@@ -66,8 +66,9 @@ public synchronized StorageStatistics get(String name) {
    * @param provider    An object which can create a new StorageStatistics
    *                      object if needed.
    * @return            The StorageStatistics object with the given name.
-   * @throws RuntimeException  If the StorageStatisticsProvider provides a new
+   * @throws RuntimeException  If the StorageStatisticsProvider provides a null
-   *                           StorageStatistics object with the wrong name.
+   *                           object or a new StorageStatistics object with the
+   *                           wrong name.
    */
   public synchronized StorageStatistics put(String name,
       StorageStatisticsProvider provider) {
@@ -78,6 +79,10 @@ public synchronized StorageStatistics put(String name,
       return stats;
     }
     stats = provider.provide();
+    if (stats == null) {
+      throw new RuntimeException("StorageStatisticsProvider for " + name +
+          " should not provide a null StorageStatistics object.");
+    }
     if (!stats.getName().equals(name)) {
       throw new RuntimeException("StorageStatisticsProvider for " + name +
           " provided a StorageStatistics object for " + stats.getName() +
@@ -87,6 +92,15 @@ public synchronized StorageStatistics put(String name,
     return stats;
   }
 
+  /**
+   * Reset all global storage statistics.
+   */
+  public synchronized void reset() {
+    for (StorageStatistics statistics : map.values()) {
+      statistics.reset();
+    }
+  }
+
   /**
    * Get an iterator that we can use to iterate throw all the global storage
    * statistics objects.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/StorageStatistics.java

@@ -132,8 +132,7 @@ public String getScheme() {
    * Get the value of a statistic.
    *
    * @return         null if the statistic is not being tracked or is not a
-   *                     long statistic.
+   *                 long statistic. The value of the statistic, otherwise.
-   *                 The value of the statistic, otherwise.
    */
   public abstract Long getLong(String key);
 
@@ -143,4 +142,9 @@ public String getScheme() {
    * @return         True only if the statistic is being tracked.
    */
   public abstract boolean isTracked(String key);
+
+  /**
+   * Reset all the statistic data.
+   */
+  public abstract void reset();
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/UnionStorageStatistics.java

@@ -20,6 +20,7 @@
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
+import com.google.common.base.Preconditions;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 
@@ -77,6 +78,16 @@ public void remove() {
 
   public UnionStorageStatistics(String name, StorageStatistics[] stats) {
     super(name);
+
+    Preconditions.checkArgument(name != null,
+        "The name of union storage statistics can not be null!");
+    Preconditions.checkArgument(stats != null,
+        "The stats of union storage statistics can not be null!");
+    for (StorageStatistics stat : stats) {
+      Preconditions.checkArgument(stat != null,
+          "The stats of union storage statistics can not have null element!");
+    }
+
     this.stats = stats;
   }
 
@@ -87,8 +98,8 @@ public Iterator<LongStatistic> getLongStatistics() {
 
   @Override
   public Long getLong(String key) {
-    for (int i = 0; i < stats.length; i++) {
+    for (StorageStatistics stat : stats) {
-      Long val = stats[i].getLong(key);
+      Long val = stat.getLong(key);
       if (val != null) {
         return val;
       }
@@ -103,11 +114,18 @@ public Long getLong(String key) {
    */
   @Override
   public boolean isTracked(String key) {
-    for (int i = 0; i < stats.length; i++) {
+    for (StorageStatistics stat : stats) {
-      if (stats[i].isTracked(key)) {
+      if (stat.isTracked(key)) {
         return true;
       }
     }
     return false;
   }
+
+  @Override
+  public void reset() {
+    for (StorageStatistics stat : stats) {
+      stat.reset();
+    }
+  }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestFileSystemStorageStatistics.java

@@ -69,7 +69,7 @@ public void setup() {
   }
 
   @Test
-  public void testgetLongStatistics() {
+  public void testGetLongStatistics() {
     Iterator<LongStatistic> iter = storageStatistics.getLongStatistics();
     while (iter.hasNext()) {
       final LongStatistic longStat = iter.next();

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSOpsCountStatistics.java

@@ -171,4 +171,11 @@ public boolean isTracked(String key) {
     return OpType.fromSymbol(key) != null;
   }
 
+  @Override
+  public void reset() {
+    for (AtomicLong count : opsCount.values()) {
+      count.set(0);
+    }
+  }
+
 }

hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/TestDFSOpsCountStatistics.java

@@ -23,19 +23,27 @@
 
 import org.apache.hadoop.hdfs.DFSOpsCountStatistics.OpType;
 
-import org.junit.BeforeClass;
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 
 import org.junit.rules.ExpectedException;
 import org.junit.rules.Timeout;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
 
+import static org.apache.hadoop.util.concurrent.HadoopExecutors.newFixedThreadPool;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -47,25 +55,25 @@
  */
 public class TestDFSOpsCountStatistics {
 
-  private static final DFSOpsCountStatistics STORAGE_STATISTICS =
+  private static final Logger LOG = LoggerFactory.getLogger(
-      new DFSOpsCountStatistics();
+      TestDFSOpsCountStatistics.class);
-  private static final Map<String, Long> OP_COUNTER_MAP = new HashMap<>();
   private static final String NO_SUCH_OP = "no-such-dfs-operation-dude";
 
+  private final DFSOpsCountStatistics statistics =
+      new DFSOpsCountStatistics();
+  private final Map<OpType, AtomicLong> expectedOpsCountMap = new HashMap<>();
+
   @Rule
   public final Timeout globalTimeout = new Timeout(10 * 1000);
   @Rule
   public final ExpectedException exception = ExpectedException.none();
 
-  @BeforeClass
+  @Before
-  public static void setup() {
+  public void setup() {
     for (OpType opType : OpType.values()) {
-      final Long opCount = RandomUtils.nextLong(0, 100);
+      expectedOpsCountMap.put(opType, new AtomicLong());
-      OP_COUNTER_MAP.put(opType.getSymbol(), opCount);
-      for (long i = 0; i < opCount; i++) {
-        STORAGE_STATISTICS.incrementOpCounter(opType);
-      }
     }
+    incrementOpsCountByRandomNumbers();
   }
 
   /**
@@ -84,13 +92,15 @@ public void testOpTypeSymbolsAreUnique() {
   @Test
   public void testGetLongStatistics() {
     short iterations = 0; // number of the iter.hasNext()
-    final Iterator<LongStatistic> iter = STORAGE_STATISTICS.getLongStatistics();
+    final Iterator<LongStatistic> iter = statistics.getLongStatistics();
 
     while (iter.hasNext()) {
       final LongStatistic longStat = iter.next();
       assertNotNull(longStat);
-      assertTrue(OP_COUNTER_MAP.containsKey(longStat.getName()));
+      final OpType opType = OpType.fromSymbol(longStat.getName());
-      assertEquals(OP_COUNTER_MAP.get(longStat.getName()).longValue(),
+      assertNotNull(opType);
+      assertTrue(expectedOpsCountMap.containsKey(opType));
+      assertEquals(expectedOpsCountMap.get(opType).longValue(),
           longStat.getValue());
       iterations++;
     }
@@ -101,22 +111,103 @@ public void testGetLongStatistics() {
 
   @Test
   public void testGetLong() {
-    assertNull(STORAGE_STATISTICS.getLong(NO_SUCH_OP));
+    assertNull(statistics.getLong(NO_SUCH_OP));
-
+    verifyStatistics();
-    for (OpType opType : OpType.values()) {
-      final String key = opType.getSymbol();
-      assertEquals(OP_COUNTER_MAP.get(key), STORAGE_STATISTICS.getLong(key));
-    }
   }
 
   @Test
   public void testIsTracked() {
-    assertFalse(STORAGE_STATISTICS.isTracked(NO_SUCH_OP));
+    assertFalse(statistics.isTracked(NO_SUCH_OP));
 
-    final Iterator<LongStatistic> iter = STORAGE_STATISTICS.getLongStatistics();
+    final Iterator<LongStatistic> iter = statistics.getLongStatistics();
     while (iter.hasNext()) {
       final LongStatistic longStatistic = iter.next();
-      assertTrue(STORAGE_STATISTICS.isTracked(longStatistic.getName()));
+      assertTrue(statistics.isTracked(longStatistic.getName()));
+    }
+  }
+
+  @Test
+  public void testReset() {
+    statistics.reset();
+    for (OpType opType : OpType.values()) {
+      expectedOpsCountMap.get(opType).set(0);
+    }
+
+    final Iterator<LongStatistic> iter = statistics.getLongStatistics();
+    while (iter.hasNext()) {
+      final LongStatistic longStat = iter.next();
+      assertEquals(0, longStat.getValue());
+    }
+
+    incrementOpsCountByRandomNumbers();
+    verifyStatistics();
+  }
+
+  @Test
+  public void testCurrentAccess() throws InterruptedException {
+    final int numThreads = 10;
+    final ExecutorService threadPool = newFixedThreadPool(numThreads);
+
+    try {
+      final CountDownLatch allReady = new CountDownLatch(numThreads);
+      final CountDownLatch startBlocker = new CountDownLatch(1);
+      final CountDownLatch allDone = new CountDownLatch(numThreads);
+      final AtomicReference<Throwable> childError = new AtomicReference<>();
+
+      for (int i = 0; i < numThreads; i++) {
+        threadPool.submit(new Runnable() {
+          @Override
+          public void run() {
+            allReady.countDown();
+            try {
+              startBlocker.await();
+              incrementOpsCountByRandomNumbers();
+            } catch (Throwable t) {
+              LOG.error("Child failed when calling mkdir", t);
+              childError.compareAndSet(null, t);
+            } finally {
+              allDone.countDown();
+            }
+          }
+        });
+      }
+
+      allReady.await(); // wait until all threads are ready
+      startBlocker.countDown(); // all threads start making directories
+      allDone.await(); // wait until all threads are done
+
+      assertNull("Child failed with exception.", childError.get());
+      verifyStatistics();
+    } finally {
+      threadPool.shutdownNow();
+    }
+  }
+
+  /**
+   * This is helper method to increment the statistics by random data.
+   */
+  private void incrementOpsCountByRandomNumbers() {
+    for (OpType opType : OpType.values()) {
+      final Long randomCount = RandomUtils.nextLong(0, 100);
+      expectedOpsCountMap.get(opType).addAndGet(randomCount);
+      for (long i = 0; i < randomCount; i++) {
+        statistics.incrementOpCounter(opType);
+      }
+    }
+  }
+
+  /**
+   * We have the expected ops count in {@link #expectedOpsCountMap}, and this
+   * method is to verify that its ops count is the same as the one in
+   * {@link #statistics}.
+   */
+  private void verifyStatistics() {
+    for (OpType opType : OpType.values()) {
+      assertNotNull(expectedOpsCountMap.get(opType));
+      assertNotNull(statistics.getLong(opType.getSymbol()));
+      assertEquals("Not expected count for operation " + opType.getSymbol(),
+          expectedOpsCountMap.get(opType).longValue(),
+          statistics.getLong(opType.getSymbol()).longValue());
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDistributedFileSystem.java

@@ -438,6 +438,43 @@ public void testDFSClient() throws Exception {
     }
   }
 
+  /**
+   * This is to test that the {@link FileSystem#clearStatistics()} resets all
+   * the global storage statistics.
+   */
+  @Test
+  public void testClearStatistics() throws Exception {
+    final Configuration conf = getTestConfiguration();
+    final MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
+    try {
+      cluster.waitActive();
+      FileSystem dfs = cluster.getFileSystem();
+
+      final Path dir = new Path("/testClearStatistics");
+      final long mkdirCount = getOpStatistics(OpType.MKDIRS);
+      long writeCount = DFSTestUtil.getStatistics(dfs).getWriteOps();
+      dfs.mkdirs(dir);
+      checkOpStatistics(OpType.MKDIRS, mkdirCount + 1);
+      assertEquals(++writeCount,
+          DFSTestUtil.getStatistics(dfs).getWriteOps());
+
+      final long createCount = getOpStatistics(OpType.CREATE);
+      FSDataOutputStream out = dfs.create(new Path(dir, "tmpFile"), (short)1);
+      out.write(40);
+      out.close();
+      checkOpStatistics(OpType.CREATE, createCount + 1);
+      assertEquals(++writeCount,
+          DFSTestUtil.getStatistics(dfs).getWriteOps());
+
+      FileSystem.clearStatistics();
+      checkOpStatistics(OpType.MKDIRS, 0);
+      checkOpStatistics(OpType.CREATE, 0);
+      checkStatistics(dfs, 0, 0, 0);
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
   @Test
   public void testStatistics() throws IOException {
     FileSystem.getStatistics(HdfsConstants.HDFS_URI_SCHEME,

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AStorageStatistics.java

@@ -107,4 +107,11 @@ public boolean isTracked(String key) {
     return Statistic.fromSymbol(key) != null;
   }
 
+  @Override
+  public void reset() {
+    for (AtomicLong value : opsCount.values()) {
+      value.set(0);
+    }
+  }
+
 }