HDFS-9425. Expose number of blocks per volume as a metric (Contributed by Brahma Reddy Battula)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -2024,6 +2024,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9768. Reuse ObjectMapper instance in HDFS to improve the performance.
     (Lin Yiqun via aajisaka)
 
+    HDFS-9425. Expose number of blocks per volume as a metric
+    (Brahma Reddy Battula via vinayakumarb)
+
   BUG FIXES
 
     HDFS-7501. TransactionsSinceLastCheckpoint can be negative on SBNs.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java

@@ -30,6 +30,7 @@
 import java.io.Writer;
 import java.util.Iterator;
 import java.util.Scanner;
+import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.logging.Log;
@@ -86,6 +87,7 @@ class BlockPoolSlice {
   private final boolean deleteDuplicateReplicas;
   private static final String REPLICA_CACHE_FILE = "replicas";
   private final long replicaCacheExpiry = 5*60*1000;
+  private AtomicLong numOfBlocks = new AtomicLong();
   private final long cachedDfsUsedCheckTime;
   private final Timer timer;
 
@@ -273,7 +275,11 @@ void saveDfsUsed() {
    */
   File createTmpFile(Block b) throws IOException {
     File f = new File(tmpDir, b.getBlockName());
-    return DatanodeUtil.createTmpFile(b, f);
+    File tmpFile = DatanodeUtil.createTmpFile(b, f);
+    // If any exception during creation, its expected that counter will not be
+    // incremented, So no need to decrement
+    incrNumBlocks();
+    return tmpFile;
   }
 
   /**
@@ -282,7 +288,11 @@ File createTmpFile(Block b) throws IOException {
    */
   File createRbwFile(Block b) throws IOException {
     File f = new File(rbwDir, b.getBlockName());
-    return DatanodeUtil.createTmpFile(b, f);
+    File rbwFile = DatanodeUtil.createTmpFile(b, f);
+    // If any exception during creation, its expected that counter will not be
+    // incremented, So no need to decrement
+    incrNumBlocks();
+    return rbwFile;
   }
 
   File addFinalizedBlock(Block b, File f) throws IOException {
@@ -493,6 +503,9 @@ private void addReplicaToReplicasMap(Block block, ReplicaMap volumeMap,
     } else {
       lazyWriteReplicaMap.discardReplica(bpid, blockId, false);
     }
+    if (oldReplica == null) {
+      incrNumBlocks();
+    }
   }
   
 
@@ -825,4 +838,16 @@ private void saveReplicas(BlockListAsLongs blocksListToPersist) {
       }
     }
   }
+
+  void incrNumBlocks() {
+    numOfBlocks.incrementAndGet();
+  }
+
+  void decrNumBlocks() {
+    numOfBlocks.decrementAndGet();
+  }
+
+  public long getNumOfBlocks() {
+    return numOfBlocks.get();
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java

@@ -965,6 +965,11 @@ public ReplicaInfo moveBlockAcrossStorage(ExtendedBlock block,
       newReplicaInfo.setNumBytes(blockFiles[1].length());
       // Finalize the copied files
       newReplicaInfo = finalizeReplica(block.getBlockPoolId(), newReplicaInfo);
+      synchronized (this) {
+        // Increment numBlocks here as this block moved without knowing to BPS
+        FsVolumeImpl volume = (FsVolumeImpl) newReplicaInfo.getVolume();
+        volume.getBlockPoolSlice(block.getBlockPoolId()).incrNumBlocks();
+      }
 
       removeOldReplica(replicaInfo, newReplicaInfo, oldBlockFile, oldMetaFile,
           oldBlockFile.length(), oldMetaFile.length(), block.getBlockPoolId());
@@ -2599,6 +2604,7 @@ private static class VolumeInfo {
     final long reservedSpace; // size of space reserved for non-HDFS
     final long reservedSpaceForReplicas; // size of space reserved RBW or
                                     // re-replication
+    final long numBlocks;
 
     VolumeInfo(FsVolumeImpl v, long usedSpace, long freeSpace) {
       this.directory = v.toString();
@@ -2606,6 +2612,7 @@ private static class VolumeInfo {
       this.freeSpace = freeSpace;
       this.reservedSpace = v.getReserved();
       this.reservedSpaceForReplicas = v.getReservedForReplicas();
+      this.numBlocks = v.getNumBlocks();
     }
   }  
 
@@ -2640,6 +2647,7 @@ public Map<String, Object> getVolumeInfoMap() {
       innerInfo.put("freeSpace", v.freeSpace);
       innerInfo.put("reservedSpace", v.reservedSpace);
       innerInfo.put("reservedSpaceForReplicas", v.reservedSpaceForReplicas);
+      innerInfo.put("numBlocks", v.numBlocks);
       info.put(v.directory, innerInfo);
     }
     return info;
@@ -2728,8 +2736,8 @@ public void onCompleteLazyPersist(String bpId, long blockId,
     synchronized (FsDatasetImpl.this) {
       ramDiskReplicaTracker.recordEndLazyPersist(bpId, blockId, savedFiles);
 
-      targetVolume.incDfsUsed(bpId,
+      targetVolume.incDfsUsedAndNumBlocks(bpId, savedFiles[0].length()
-          savedFiles[0].length() + savedFiles[1].length());
+          + savedFiles[1].length());
 
       // Update metrics (ignore the metadata file size)
       datanode.getMetrics().incrRamDiskBlocksLazyPersisted();

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -284,21 +284,35 @@ File getTmpDir(String bpid) throws IOException {
   }
 
   void onBlockFileDeletion(String bpid, long value) {
-    decDfsUsed(bpid, value);
+    decDfsUsedAndNumBlocks(bpid, value, true);
     if (isTransientStorage()) {
       dataset.releaseLockedMemory(value, true);
     }
   }
 
   void onMetaFileDeletion(String bpid, long value) {
-    decDfsUsed(bpid, value);
+    decDfsUsedAndNumBlocks(bpid, value, false);
   }
 
-  private void decDfsUsed(String bpid, long value) {
+  private void decDfsUsedAndNumBlocks(String bpid, long value,
+                                      boolean blockFileDeleted) {
     synchronized(dataset) {
       BlockPoolSlice bp = bpSlices.get(bpid);
       if (bp != null) {
         bp.decDfsUsed(value);
+        if (blockFileDeleted) {
+          bp.decrNumBlocks();
+        }
+      }
+    }
+  }
+
+  void incDfsUsedAndNumBlocks(String bpid, long value) {
+    synchronized (dataset) {
+      BlockPoolSlice bp = bpSlices.get(bpid);
+      if (bp != null) {
+        bp.incDfsUsed(value);
+        bp.incrNumBlocks();
       }
     }
   }
@@ -847,7 +861,15 @@ void getVolumeMap(String bpid, ReplicaMap volumeMap,
       throws IOException {
     getBlockPoolSlice(bpid).getVolumeMap(volumeMap, ramDiskReplicaMap);
   }
-  
+
+  long getNumBlocks() {
+    long numBlocks = 0;
+    for (BlockPoolSlice s : bpSlices.values()) {
+      numBlocks += s.getNumOfBlocks();
+    }
+    return numBlocks;
+  }
+
   @Override
   public String toString() {
     return currentDir.getAbsolutePath();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMXBean.java

@@ -18,15 +18,23 @@
 package org.apache.hadoop.hdfs.server.datanode;
 
 import java.lang.management.ManagementFactory;
+import java.util.Collection;
 import java.util.List;
+import java.util.Map;
 
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.junit.Assert;
 import org.junit.Test;
+import org.mortbay.util.ajax.JSON;
+
+import static org.junit.Assert.assertEquals;
 
 /**
  * Class for testing {@link DataNodeMXBean} implementation
@@ -84,4 +92,51 @@ public void testDataNodeMXBean() throws Exception {
   private static String replaceDigits(final String s) {
     return s.replaceAll("[0-9]+", "_DIGITS_");
   }
+
+  @Test
+  public void testDataNodeMXBeanBlockCount() throws Exception {
+    Configuration conf = new Configuration();
+    MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
+
+    try {
+      List<DataNode> datanodes = cluster.getDataNodes();
+      assertEquals(datanodes.size(), 1);
+
+      MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
+      ObjectName mxbeanName =
+              new ObjectName("Hadoop:service=DataNode,name=DataNodeInfo");
+      FileSystem fs = cluster.getFileSystem();
+      for (int i = 0; i < 5; i++) {
+        DFSTestUtil.createFile(fs, new Path("/tmp.txt" + i), 1024, (short) 1,
+                1L);
+      }
+      assertEquals("Before restart DN", 5, getTotalNumBlocks(mbs, mxbeanName));
+      cluster.restartDataNode(0);
+      cluster.waitActive();
+      assertEquals("After restart DN", 5, getTotalNumBlocks(mbs, mxbeanName));
+      fs.delete(new Path("/tmp.txt1"), true);
+      // Wait till replica gets deleted on disk.
+      Thread.sleep(5000);
+      assertEquals("After delete one file", 4,
+              getTotalNumBlocks(mbs, mxbeanName));
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
+
+  @SuppressWarnings("unchecked")
+  int getTotalNumBlocks(MBeanServer mbs, ObjectName mxbeanName)
+          throws Exception {
+    int totalBlocks = 0;
+    String volumeInfo = (String) mbs.getAttribute(mxbeanName, "VolumeInfo");
+    Map<?, ?> m = (Map<?, ?>) JSON.parse(volumeInfo);
+    Collection<Map<String, Long>> values =
+            (Collection<Map<String, Long>>) m.values();
+    for (Map<String, Long> volumeInfoMap : values) {
+      totalBlocks += volumeInfoMap.get("numBlocks");
+    }
+    return totalBlocks;
+  }
 }