HDFS-4645. Move from randomly generated block ID to sequentially generated block ID. Contributed by Arpit Agarwal

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1501993 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -206,6 +206,9 @@ Release 2.1.0-beta - 2013-07-02
     HDFS-4932. Avoid a wide line on the name node webUI if we have more Journal
     nodes. (Fengdong Yu via cnauroth)
 
+    HDFS-4645. Move from randomly generated block ID to sequentially generated
+    block ID.  (Arpit Agarwal via szetszwo)
+
   OPTIMIZATIONS
 
     HDFS-4465. Optimize datanode ReplicasMap and ReplicaInfo. (atm)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/HdfsConstants.java

@@ -86,6 +86,10 @@ public class HdfsConstants {
   // An invalid transaction ID that will never be seen in a real namesystem.
   public static final long INVALID_TXID = -12345;
 
+  // Number of generation stamps reserved for legacy blocks.
+  public static final long RESERVED_GENERATION_STAMPS_V1 =
+      1024L * 1024 * 1024 * 1024;
+
   /**
    * URI Scheme for hdfs://namenode/ URIs.
    */

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutVersion.java

@@ -102,9 +102,9 @@ public class LayoutVersion {
     RESERVED_REL1_3_0(-44, -41,
         "Reserved for release 1.3.0", true, ADD_INODE_ID, SNAPSHOT),
     OPTIMIZE_SNAPSHOT_INODES(-45, -43,
-        "Reduce snapshot inode memory footprint", false);
-
-
+        "Reduce snapshot inode memory footprint", false),
+    SEQUENTIAL_BLOCK_ID(-46, "Allocate block IDs sequentially and store " +
+        "block IDs in the edits log and image files");
     
     final int lv;
     final int ancestorLV;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java

@@ -1735,7 +1735,7 @@ public class BlockManager {
       ReplicaState reportedState = itBR.getCurrentReplicaState();
       
       if (shouldPostponeBlocksFromFuture &&
-          namesystem.isGenStampInFuture(iblk.getGenerationStamp())) {
+          namesystem.isGenStampInFuture(iblk)) {
         queueReportedBlock(node, iblk, reportedState,
             QUEUE_REASON_FUTURE_GENSTAMP);
         continue;
@@ -1857,7 +1857,7 @@ public class BlockManager {
     }
   
     if (shouldPostponeBlocksFromFuture &&
-        namesystem.isGenStampInFuture(block.getGenerationStamp())) {
+        namesystem.isGenStampInFuture(block)) {
       queueReportedBlock(dn, block, reportedState,
           QUEUE_REASON_FUTURE_GENSTAMP);
       return null;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/OutOfV1GenerationStampsException.java

@@ -0,0 +1,38 @@
+/**
+ * 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.hdfs.server.blockmanagement;
+
+import java.io.IOException;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/**
+ * This exception is thrown when the name node runs out of V1 generation
+ * stamps.
+ *
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class OutOfV1GenerationStampsException extends IOException {
+  private static final long serialVersionUID = 1L;
+
+  public OutOfV1GenerationStampsException() {
+    super("Out of V1 (legacy) generation stamps\n");
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java

@@ -60,7 +60,6 @@ import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOldOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenewDelegationTokenOp;
-import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetOwnerOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetPermissionsOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetQuotaOp;
@@ -69,6 +68,9 @@ import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SymlinkOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.TimesOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateBlocksOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateMasterKeyOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV1Op;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV2Op;
 import org.apache.hadoop.hdfs.server.namenode.JournalSet.JournalAndStream;
 import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
 import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
@@ -800,12 +802,30 @@ public class FSEditLog implements LogsPurgeable {
     logEdit(op);
   }
 
-  /** 
+  /**
+   * Add legacy block generation stamp record to edit log
+   */
+  void logGenerationStampV1(long genstamp) {
+    SetGenstampV1Op op = SetGenstampV1Op.getInstance(cache.get())
+        .setGenerationStamp(genstamp);
+    logEdit(op);
+  }
+
+  /**
    * Add generation stamp record to edit log
    */
-  void logGenerationStamp(long genstamp) {
-    SetGenstampOp op = SetGenstampOp.getInstance(cache.get())
-      .setGenerationStamp(genstamp);
+  void logGenerationStampV2(long genstamp) {
+    SetGenstampV2Op op = SetGenstampV2Op.getInstance(cache.get())
+        .setGenerationStamp(genstamp);
+    logEdit(op);
+  }
+
+  /**
+   * Record a newly allocated block ID in the edit log
+   */
+  void logAllocateBlockId(long blockId) {
+    AllocateBlockIdOp op = AllocateBlockIdOp.getInstance(cache.get())
+      .setBlockId(blockId);
     logEdit(op);
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java

@@ -57,7 +57,6 @@ import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOldOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenewDelegationTokenOp;
-import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetNSQuotaOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetOwnerOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetPermissionsOp;
@@ -67,6 +66,9 @@ import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SymlinkOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.TimesOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateBlocksOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateMasterKeyOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV1Op;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV2Op;
 import org.apache.hadoop.hdfs.server.namenode.INode.BlocksMapUpdateInfo;
 import org.apache.hadoop.hdfs.server.namenode.LeaseManager.Lease;
 import org.apache.hadoop.hdfs.util.Holder;
@@ -406,9 +408,9 @@ public class FSEditLogLoader {
                              mkdirOp.timestamp);
       break;
     }
-    case OP_SET_GENSTAMP: {
-      SetGenstampOp setGenstampOp = (SetGenstampOp)op;
-      fsNamesys.setGenerationStamp(setGenstampOp.genStamp);
+    case OP_SET_GENSTAMP_V1: {
+      SetGenstampV1Op setGenstampV1Op = (SetGenstampV1Op)op;
+      fsNamesys.setGenerationStampV1(setGenstampV1Op.genStampV1);
       break;
     }
     case OP_SET_PERMISSIONS: {
@@ -554,6 +556,16 @@ public class FSEditLogLoader {
           disallowSnapshotOp.snapshotRoot);
       break;
     }
+    case OP_SET_GENSTAMP_V2: {
+      SetGenstampV2Op setGenstampV2Op = (SetGenstampV2Op) op;
+      fsNamesys.setGenerationStampV2(setGenstampV2Op.genStampV2);
+      break;
+    }
+    case OP_ALLOCATE_BLOCK_ID: {
+      AllocateBlockIdOp allocateBlockIdOp = (AllocateBlockIdOp) op;
+      fsNamesys.setLastAllocatedBlockId(allocateBlockIdOp.blockId);
+      break;
+    }
     default:
       throw new IOException("Invalid operation read " + op.opCode);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java

@@ -90,7 +90,7 @@ public abstract class FSEditLogOp {
       inst.put(OP_RENAME_OLD, new RenameOldOp());
       inst.put(OP_DELETE, new DeleteOp());
       inst.put(OP_MKDIR, new MkdirOp());
-      inst.put(OP_SET_GENSTAMP, new SetGenstampOp());
+      inst.put(OP_SET_GENSTAMP_V1, new SetGenstampV1Op());
       inst.put(OP_SET_PERMISSIONS, new SetPermissionsOp());
       inst.put(OP_SET_OWNER, new SetOwnerOp());
       inst.put(OP_SET_NS_QUOTA, new SetNSQuotaOp());
@@ -116,6 +116,8 @@ public abstract class FSEditLogOp {
       inst.put(OP_CREATE_SNAPSHOT, new CreateSnapshotOp());
       inst.put(OP_DELETE_SNAPSHOT, new DeleteSnapshotOp());
       inst.put(OP_RENAME_SNAPSHOT, new RenameSnapshotOp());
+      inst.put(OP_SET_GENSTAMP_V2, new SetGenstampV2Op());
+      inst.put(OP_ALLOCATE_BLOCK_ID, new AllocateBlockIdOp());
     }
     
     public FSEditLogOp get(FSEditLogOpCodes opcode) {
@@ -1054,39 +1056,39 @@ public abstract class FSEditLogOp {
     }
   }
 
-  static class SetGenstampOp extends FSEditLogOp {
-    long genStamp;
+  static class SetGenstampV1Op extends FSEditLogOp {
+    long genStampV1;
 
-    private SetGenstampOp() {
-      super(OP_SET_GENSTAMP);
+    private SetGenstampV1Op() {
+      super(OP_SET_GENSTAMP_V1);
     }
 
-    static SetGenstampOp getInstance(OpInstanceCache cache) {
-      return (SetGenstampOp)cache.get(OP_SET_GENSTAMP);
+    static SetGenstampV1Op getInstance(OpInstanceCache cache) {
+      return (SetGenstampV1Op)cache.get(OP_SET_GENSTAMP_V1);
     }
 
-    SetGenstampOp setGenerationStamp(long genStamp) {
-      this.genStamp = genStamp;
+    SetGenstampV1Op setGenerationStamp(long genStamp) {
+      this.genStampV1 = genStamp;
       return this;
     }
-    
+
     @Override
-    public 
+    public
     void writeFields(DataOutputStream out) throws IOException {
-      FSImageSerialization.writeLong(genStamp, out);
+      FSImageSerialization.writeLong(genStampV1, out);
     }
-    
+
     @Override
     void readFields(DataInputStream in, int logVersion)
         throws IOException {
-      this.genStamp = FSImageSerialization.readLong(in);
+      this.genStampV1 = FSImageSerialization.readLong(in);
     }
 
     @Override
     public String toString() {
       StringBuilder builder = new StringBuilder();
-      builder.append("SetGenstampOp [genStamp=");
-      builder.append(genStamp);
+      builder.append("SetGenstampOp [GenStamp=");
+      builder.append(genStampV1);
       builder.append(", opCode=");
       builder.append(opCode);
       builder.append(", txid=");
@@ -1094,15 +1096,119 @@ public abstract class FSEditLogOp {
       builder.append("]");
       return builder.toString();
     }
-    
+
     @Override
     protected void toXml(ContentHandler contentHandler) throws SAXException {
       XMLUtils.addSaxString(contentHandler, "GENSTAMP",
-          Long.valueOf(genStamp).toString());
+                            Long.valueOf(genStampV1).toString());
     }
-    
+
+    @Override void fromXml(Stanza st) throws InvalidXmlException {
+      this.genStampV1 = Long.valueOf(st.getValue("GENSTAMP"));
+    }
+  }
+
+  static class SetGenstampV2Op extends FSEditLogOp {
+    long genStampV2;
+
+    private SetGenstampV2Op() {
+      super(OP_SET_GENSTAMP_V2);
+    }
+
+    static SetGenstampV2Op getInstance(OpInstanceCache cache) {
+      return (SetGenstampV2Op)cache.get(OP_SET_GENSTAMP_V2);
+    }
+
+    SetGenstampV2Op setGenerationStamp(long genStamp) {
+      this.genStampV2 = genStamp;
+      return this;
+    }
+
+    @Override
+    public
+    void writeFields(DataOutputStream out) throws IOException {
+      FSImageSerialization.writeLong(genStampV2, out);
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion)
+        throws IOException {
+      this.genStampV2 = FSImageSerialization.readLong(in);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("SetGenstampV2Op [GenStampV2=");
+      builder.append(genStampV2);
+      builder.append(", opCode=");
+      builder.append(opCode);
+      builder.append(", txid=");
+      builder.append(txid);
+      builder.append("]");
+      return builder.toString();
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      XMLUtils.addSaxString(contentHandler, "GENSTAMPV2",
+                            Long.valueOf(genStampV2).toString());
+    }
+
+    @Override void fromXml(Stanza st) throws InvalidXmlException {
+      this.genStampV2 = Long.valueOf(st.getValue("GENSTAMPV2"));
+    }
+  }
+
+  static class AllocateBlockIdOp extends FSEditLogOp {
+    long blockId;
+
+    private AllocateBlockIdOp() {
+      super(OP_ALLOCATE_BLOCK_ID);
+    }
+
+    static AllocateBlockIdOp getInstance(OpInstanceCache cache) {
+      return (AllocateBlockIdOp)cache.get(OP_ALLOCATE_BLOCK_ID);
+    }
+
+    AllocateBlockIdOp setBlockId(long blockId) {
+      this.blockId = blockId;
+      return this;
+    }
+
+    @Override
+    public
+    void writeFields(DataOutputStream out) throws IOException {
+      FSImageSerialization.writeLong(blockId, out);
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion)
+        throws IOException {
+      this.blockId = FSImageSerialization.readLong(in);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("AllocateBlockIdOp [blockId=");
+      builder.append(blockId);
+      builder.append(", opCode=");
+      builder.append(opCode);
+      builder.append(", txid=");
+      builder.append(txid);
+      builder.append("]");
+      return builder.toString();
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      XMLUtils.addSaxString(contentHandler, "BLOCK_ID",
+                            Long.valueOf(blockId).toString());
+    }
+
     @Override void fromXml(Stanza st) throws InvalidXmlException {
-      this.genStamp = Long.valueOf(st.getValue("GENSTAMP"));
+      this.blockId = Long.valueOf(st.getValue("BLOCK_ID"));
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOpCodes.java

@@ -41,7 +41,7 @@ public enum FSEditLogOpCodes {
   OP_SET_PERMISSIONS            ((byte)  7),
   OP_SET_OWNER                  ((byte)  8),
   OP_CLOSE                      ((byte)  9),
-  OP_SET_GENSTAMP               ((byte) 10),
+  OP_SET_GENSTAMP_V1            ((byte) 10),
   OP_SET_NS_QUOTA               ((byte) 11), // obsolete
   OP_CLEAR_NS_QUOTA             ((byte) 12), // obsolete
   OP_TIMES                      ((byte) 13), // set atime, mtime
@@ -61,8 +61,9 @@ public enum FSEditLogOpCodes {
   OP_DELETE_SNAPSHOT            ((byte) 27),
   OP_RENAME_SNAPSHOT            ((byte) 28),
   OP_ALLOW_SNAPSHOT             ((byte) 29),
-  OP_DISALLOW_SNAPSHOT          ((byte) 30);
-
+  OP_DISALLOW_SNAPSHOT          ((byte) 30),
+  OP_SET_GENSTAMP_V2            ((byte) 31),
+  OP_ALLOCATE_BLOCK_ID          ((byte) 32);
   private byte opCode;
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java

@@ -95,7 +95,6 @@ public class FSImage implements Closeable {
   final private Configuration conf;
 
   protected NNStorageRetentionManager archivalManager;
-  protected IdGenerator blockIdGenerator;
 
   /**
    * Construct an FSImage
@@ -141,9 +140,6 @@ public class FSImage implements Closeable {
     Preconditions.checkState(fileCount == 1,
         "FSImage.format should be called with an uninitialized namesystem, has " +
         fileCount + " files");
-    // BlockIdGenerator is defined during formatting
-    // currently there is only one BlockIdGenerator
-    blockIdGenerator = createBlockIdGenerator(fsn);
     NamespaceInfo ns = NNStorage.newNamespaceInfo();
     ns.clusterID = clusterId;
     
@@ -814,9 +810,6 @@ public class FSImage implements Closeable {
     FSImageFormat.Loader loader = new FSImageFormat.Loader(
         conf, target);
     loader.load(curFile);
-    // BlockIdGenerator is determined after loading image
-    // currently there is only one BlockIdGenerator
-    blockIdGenerator = createBlockIdGenerator(target);
     target.setBlockPoolId(this.getBlockPoolID());
 
     // Check that the image digest we loaded matches up with what
@@ -1249,12 +1242,4 @@ public class FSImage implements Closeable {
   public synchronized long getMostRecentCheckpointTxId() {
     return storage.getMostRecentCheckpointTxId();
   }
-
-  public long getUniqueBlockId() {
-    return blockIdGenerator.nextValue();
-  }
-
-  public IdGenerator createBlockIdGenerator(FSNamesystem fsn) {
-    return new RandomBlockIdGenerator(fsn);
-  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java

@@ -70,8 +70,10 @@ import org.apache.hadoop.io.Text;
  * <pre>
  * FSImage {
  *   layoutVersion: int, namespaceID: int, numberItemsInFSDirectoryTree: long,
- *   namesystemGenerationStamp: long, transactionID: long, 
- *   snapshotCounter: int, numberOfSnapshots: int, numOfSnapshottableDirs: int,
+ *   namesystemGenerationStampV1: long, namesystemGenerationStampV2: long,
+ *   generationStampAtBlockIdSwitch:long, lastAllocatedBlockId:
+ *   long transactionID: long, snapshotCounter: int, numberOfSnapshots: int,
+ *   numOfSnapshottableDirs: int,
  *   {FSDirectoryTree, FilesUnderConstruction, SecretManagerState} (can be compressed)
  * }
  * 
@@ -257,10 +259,30 @@ public class FSImageFormat {
 
         long numFiles = in.readLong();
 
-        // read in the last generation stamp.
+        // read in the last generation stamp for legacy blocks.
         long genstamp = in.readLong();
-        namesystem.setGenerationStamp(genstamp); 
+        namesystem.setGenerationStampV1(genstamp);
         
+        if (LayoutVersion.supports(Feature.SEQUENTIAL_BLOCK_ID, imgVersion)) {
+          // read the starting generation stamp for sequential block IDs
+          genstamp = in.readLong();
+          namesystem.setGenerationStampV2(genstamp);
+
+          // read the last generation stamp for blocks created after
+          // the switch to sequential block IDs.
+          long stampAtIdSwitch = in.readLong();
+          namesystem.setGenerationStampV1Limit(stampAtIdSwitch);
+
+          // read the max sequential block ID.
+          long maxSequentialBlockId = in.readLong();
+          namesystem.setLastAllocatedBlockId(maxSequentialBlockId);
+        } else {
+          long startingGenStamp = namesystem.upgradeGenerationStampToV2();
+          // This is an upgrade.
+          LOG.info("Upgrading to sequential block IDs. Generation stamp " +
+                   "for new blocks set to " + startingGenStamp);
+        }
+
         // read the transaction ID of the last edit represented by
         // this image
         if (LayoutVersion.supports(Feature.STORED_TXIDS, imgVersion)) {
@@ -884,9 +906,13 @@ public class FSImageFormat {
         out.writeInt(sourceNamesystem.unprotectedGetNamespaceInfo()
             .getNamespaceID());
         out.writeLong(fsDir.rootDir.numItemsInTree());
-        out.writeLong(sourceNamesystem.getGenerationStamp());
+        out.writeLong(sourceNamesystem.getGenerationStampV1());
+        out.writeLong(sourceNamesystem.getGenerationStampV2());
+        out.writeLong(sourceNamesystem.getGenerationStampAtblockIdSwitch());
+        out.writeLong(sourceNamesystem.getLastAllocatedBlockId());
         out.writeLong(context.getTxId());
         out.writeLong(sourceNamesystem.getLastInodeId());
+
         
         sourceNamesystem.getSnapshotManager().write(out);
         

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -156,12 +156,7 @@ import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager.AccessMode;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager;
-import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
-import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
-import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
-import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
-import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager;
-import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStatistics;
+import org.apache.hadoop.hdfs.server.blockmanagement.*;
 import org.apache.hadoop.hdfs.server.common.GenerationStamp;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.BlockUCState;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NamenodeRole;
@@ -364,9 +359,32 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
   private final long maxBlocksPerFile;     // maximum # of blocks per file
 
   /**
-   * The global generation stamp for this file system. 
+   * The global generation stamp for legacy blocks with randomly
+   * generated block IDs.
    */
-  private final GenerationStamp generationStamp = new GenerationStamp();
+  private final GenerationStamp generationStampV1 = new GenerationStamp();
+
+  /**
+   * The global generation stamp for this file system.
+   */
+  private final GenerationStamp generationStampV2 = new GenerationStamp();
+
+  /**
+   * The value of the generation stamp when the first switch to sequential
+   * block IDs was made. Blocks with generation stamps below this value
+   * have randomly allocated block IDs. Blocks with generation stamps above
+   * this value had sequentially allocated block IDs. Read from the fsImage
+   * (or initialized as an offset from the V1 (legacy) generation stamp on
+   * upgrade).
+   */
+  private long generationStampV1Limit =
+      GenerationStamp.GRANDFATHER_GENERATION_STAMP;
+
+  /**
+   * The global block ID space for this file system.
+   */
+  @VisibleForTesting
+  private final SequentialBlockIdGenerator blockIdGenerator;
 
   // precision of access times.
   private final long accessTimePrecision;
@@ -426,7 +444,11 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
   void clear() {
     dir.reset();
     dtSecretManager.reset();
-    generationStamp.setCurrentValue(GenerationStamp.LAST_RESERVED_STAMP);
+    generationStampV1.setCurrentValue(GenerationStamp.LAST_RESERVED_STAMP);
+    generationStampV2.setCurrentValue(GenerationStamp.LAST_RESERVED_STAMP);
+    blockIdGenerator.setCurrentValue(
+        SequentialBlockIdGenerator.LAST_RESERVED_BLOCK_ID);
+    generationStampV1Limit = GenerationStamp.GRANDFATHER_GENERATION_STAMP;
     leaseManager.removeAllLeases();
     inodeId.setCurrentValue(INodeId.LAST_RESERVED_ID);
   }
@@ -528,9 +550,9 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
    * 
    * Note that this does not load any data off of disk -- if you would
    * like that behavior, use {@link #loadFromDisk(Configuration)}
-
-   * @param fnImage The FSImage to associate with
+   *
    * @param conf configuration
+   * @param fsImage The FSImage to associate with
    * @throws IOException on bad configuration
    */
   FSNamesystem(Configuration conf, FSImage fsImage) throws IOException {
@@ -541,6 +563,7 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
 
       this.blockManager = new BlockManager(this, this, conf);
       this.datanodeStatistics = blockManager.getDatanodeManager().getDatanodeStatistics();
+      this.blockIdGenerator = new SequentialBlockIdGenerator(this.blockManager);
 
       this.fsOwner = UserGroupInformation.getCurrentUser();
       this.fsOwnerShortUserName = fsOwner.getShortUserName();
@@ -2658,9 +2681,9 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
    */
   Block createNewBlock() throws IOException {
     assert hasWriteLock();
-    Block b = new Block(getFSImage().getUniqueBlockId(), 0, 0); 
+    Block b = new Block(nextBlockId(), 0, 0);
     // Increment the generation stamp for every new block.
-    b.setGenerationStamp(nextGenerationStamp());
+    b.setGenerationStamp(nextGenerationStamp(false));
     return b;
   }
 
@@ -3356,7 +3379,7 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
         uc.setExpectedLocations(blockManager.getNodes(lastBlock));
       }
       // start recovery of the last block for this file
-      long blockRecoveryId = nextGenerationStamp();
+      long blockRecoveryId = nextGenerationStamp(isLegacyBlock(uc));
       lease = reassignLease(lease, src, recoveryLeaseHolder, pendingFile);
       uc.initializeBlockRecovery(blockRecoveryId);
       leaseManager.renewLease(lease);
@@ -5007,34 +5030,164 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
   }
 
   /**
-   * Sets the generation stamp for this filesystem
+   * Sets the current generation stamp for legacy blocks
+   */
+  void setGenerationStampV1(long stamp) {
+    generationStampV1.setCurrentValue(stamp);
+  }
+
+  /**
+   * Gets the current generation stamp for legacy blocks
+   */
+  long getGenerationStampV1() {
+    return generationStampV1.getCurrentValue();
+  }
+
+  /**
+   * Gets the current generation stamp for this filesystem
+   */
+  void setGenerationStampV2(long stamp) {
+    generationStampV2.setCurrentValue(stamp);
+  }
+
+  /**
+   * Gets the current generation stamp for this filesystem
+   */
+  long getGenerationStampV2() {
+    return generationStampV2.getCurrentValue();
+  }
+
+  /**
+   * Upgrades the generation stamp for the filesystem
+   * by reserving a sufficient range for all existing blocks.
+   * Should be invoked only during the first upgrade to
+   * sequential block IDs.
+   */
+  long upgradeGenerationStampToV2() {
+    Preconditions.checkState(generationStampV2.getCurrentValue() ==
+        GenerationStamp.LAST_RESERVED_STAMP);
+
+    generationStampV2.skipTo(
+        generationStampV1.getCurrentValue() +
+        HdfsConstants.RESERVED_GENERATION_STAMPS_V1);
+
+    generationStampV1Limit = generationStampV2.getCurrentValue();
+    return generationStampV2.getCurrentValue();
+  }
+
+  /**
+   * Sets the generation stamp that delineates random and sequentially
+   * allocated block IDs.
+   * @param stamp
+   */
+  void setGenerationStampV1Limit(long stamp) {
+    Preconditions.checkState(generationStampV1Limit ==
+                             GenerationStamp.GRANDFATHER_GENERATION_STAMP);
+    generationStampV1Limit = stamp;
+  }
+
+  /**
+   * Gets the value of the generation stamp that delineates sequential
+   * and random block IDs.
    */
-  void setGenerationStamp(long stamp) {
-    generationStamp.setCurrentValue(stamp);
+  long getGenerationStampAtblockIdSwitch() {
+    return generationStampV1Limit;
+  }
+
+  @VisibleForTesting
+  SequentialBlockIdGenerator getBlockIdGenerator() {
+    return blockIdGenerator;
+  }
+
+  /**
+   * Sets the maximum allocated block ID for this filesystem. This is
+   * the basis for allocating new block IDs.
+   */
+  void setLastAllocatedBlockId(long blockId) {
+    blockIdGenerator.skipTo(blockId);
   }
 
   /**
-   * Gets the generation stamp for this filesystem
+   * Gets the maximum sequentially allocated block ID for this filesystem
    */
-  long getGenerationStamp() {
-    return generationStamp.getCurrentValue();
+  long getLastAllocatedBlockId() {
+    return blockIdGenerator.getCurrentValue();
   }
 
   /**
    * Increments, logs and then returns the stamp
    */
-  private long nextGenerationStamp() throws SafeModeException {
+  long nextGenerationStamp(boolean legacyBlock)
+      throws IOException, SafeModeException {
     assert hasWriteLock();
     if (isInSafeMode()) {
       throw new SafeModeException(
           "Cannot get next generation stamp", safeMode);
     }
-    final long gs = generationStamp.nextValue();
-    getEditLog().logGenerationStamp(gs);
+
+    long gs;
+    if (legacyBlock) {
+      gs = getNextGenerationStampV1();
+      getEditLog().logGenerationStampV1(gs);
+    } else {
+      gs = getNextGenerationStampV2();
+      getEditLog().logGenerationStampV2(gs);
+    }
+
     // NB: callers sync the log
     return gs;
   }
 
+  @VisibleForTesting
+  long getNextGenerationStampV1() throws IOException {
+    long genStampV1 = generationStampV1.nextValue();
+
+    if (genStampV1 >= generationStampV1Limit) {
+      // We ran out of generation stamps for legacy blocks. In practice, it
+      // is extremely unlikely as we reserved 1T v1 generation stamps. The
+      // result is that we can no longer append to the legacy blocks that
+      // were created before the upgrade to sequential block IDs.
+      throw new OutOfV1GenerationStampsException();
+    }
+
+    return genStampV1;
+  }
+
+  @VisibleForTesting
+  long getNextGenerationStampV2() {
+    return generationStampV2.nextValue();
+  }
+
+  long getGenerationStampV1Limit() {
+    return generationStampV1Limit;
+  }
+
+  /**
+   * Determine whether the block ID was randomly generated (legacy) or
+   * sequentially generated. The generation stamp value is used to
+   * make the distinction.
+   * @param block
+   * @return true if the block ID was randomly generated, false otherwise.
+   */
+  boolean isLegacyBlock(Block block) {
+    return block.getGenerationStamp() < getGenerationStampV1Limit();
+  }
+
+  /**
+   * Increments, logs and then returns the block ID
+   */
+  private long nextBlockId() throws SafeModeException {
+    assert hasWriteLock();
+    if (isInSafeMode()) {
+      throw new SafeModeException(
+          "Cannot get next block ID", safeMode);
+    }
+    final long blockId = blockIdGenerator.nextValue();
+    getEditLog().logAllocateBlockId(blockId);
+    // NB: callers sync the log
+    return blockId;
+  }
+
   private INodeFileUnderConstruction checkUCBlock(ExtendedBlock block,
       String clientName) throws IOException {
     assert hasWriteLock();
@@ -5115,7 +5268,8 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
       checkUCBlock(block, clientName);
   
       // get a new generation stamp and an access token
-      block.setGenerationStamp(nextGenerationStamp());
+      block.setGenerationStamp(
+          nextGenerationStamp(isLegacyBlock(block.getLocalBlock())));
       locatedBlock = new LocatedBlock(block, new DatanodeInfo[0]);
       blockManager.setBlockToken(locatedBlock, AccessMode.WRITE);
     } finally {
@@ -5130,7 +5284,7 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
    * Update a pipeline for a block under construction
    * 
    * @param clientName the name of the client
-   * @param oldblock and old block
+   * @param oldBlock and old block
    * @param newBlock a new block with a new generation stamp and length
    * @param newNodes datanodes in the pipeline
    * @throws IOException if any error occurs
@@ -5917,9 +6071,14 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
   }
   
   @Override
-  public boolean isGenStampInFuture(long genStamp) {
-    return (genStamp > getGenerationStamp());
+  public boolean isGenStampInFuture(Block block) {
+    if (isLegacyBlock(block)) {
+      return block.getGenerationStamp() > getGenerationStampV1();
+    } else {
+      return block.getGenerationStamp() > getGenerationStampV2();
+    }
   }
+
   @VisibleForTesting
   public EditLogTailer getEditLogTailer() {
     return editLogTailer;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/Namesystem.java

@@ -18,6 +18,7 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory;
 import org.apache.hadoop.hdfs.util.RwLock;
 import org.apache.hadoop.ipc.StandbyException;
@@ -37,7 +38,7 @@ public interface Namesystem extends RwLock, SafeMode {
 
   public boolean isInStandbyState();
 
-  public boolean isGenStampInFuture(long generationStamp);
+  public boolean isGenStampInFuture(Block block);
 
   public void adjustSafeModeBlockTotals(int deltaSafe, int deltaTotal);
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/RandomBlockIdGenerator.java → hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SequentialBlockIdGenerator.java

@@ -18,27 +18,41 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import org.apache.hadoop.classification.InterfaceAudience;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
-import org.apache.hadoop.util.IdGenerator;
+import org.apache.hadoop.util.SequentialNumber;
 
 /**
- * Generator of random block IDs.
+ * Generate the next valid block ID by incrementing the maximum block
+ * ID allocated so far, starting at 2^30+1.
+ *
+ * Block IDs used to be allocated randomly in the past. Hence we may
+ * find some conflicts while stepping through the ID space sequentially.
+ * However given the sparsity of the ID space, conflicts should be rare
+ * and can be skipped over when detected.
  */
 @InterfaceAudience.Private
-public class RandomBlockIdGenerator implements IdGenerator {
+public class SequentialBlockIdGenerator extends SequentialNumber {
+  /**
+   * The last reserved block ID.
+   */
+  public static final long LAST_RESERVED_BLOCK_ID = 1024L * 1024 * 1024;
+
   private final BlockManager blockManager;
 
-  RandomBlockIdGenerator(FSNamesystem namesystem) {
-    this.blockManager = namesystem.getBlockManager();
+  SequentialBlockIdGenerator(BlockManager blockManagerRef) {
+    super(LAST_RESERVED_BLOCK_ID);
+    this.blockManager = blockManagerRef;
   }
 
   @Override // NumberGenerator
   public long nextValue() {
-    Block b = new Block(DFSUtil.getRandom().nextLong(), 0, 0); 
+    Block b = new Block(super.nextValue());
+
+    // There may be an occasional conflict with randomly generated
+    // block IDs. Skip over the conflicts.
     while(isValidBlock(b)) {
-      b.setBlockId(DFSUtil.getRandom().nextLong());
+      b.setBlockId(super.nextValue());
     }
     return b.getBlockId();
   }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java

@@ -126,7 +126,7 @@ class ImageLoaderCurrent implements ImageLoader {
                                       new SimpleDateFormat("yyyy-MM-dd HH:mm");
   private static int[] versions = { -16, -17, -18, -19, -20, -21, -22, -23,
       -24, -25, -26, -27, -28, -30, -31, -32, -33, -34, -35, -36, -37, -38, -39,
-      -40, -41, -42, -43, -44, -45};
+      -40, -41, -42, -43, -44, -45, -46 };
   private int imageVersion = 0;
   
   private final Map<Long, String> subtreeMap = new HashMap<Long, String>();
@@ -165,6 +165,12 @@ class ImageLoaderCurrent implements ImageLoader {
 
       v.visit(ImageElement.GENERATION_STAMP, in.readLong());
 
+      if (LayoutVersion.supports(Feature.SEQUENTIAL_BLOCK_ID, imageVersion)) {
+        v.visit(ImageElement.GENERATION_STAMP_V2, in.readLong());
+        v.visit(ImageElement.GENERATION_STAMP_V1_LIMIT, in.readLong());
+        v.visit(ImageElement.LAST_ALLOCATED_BLOCK_ID, in.readLong());
+      }
+
       if (LayoutVersion.supports(Feature.STORED_TXIDS, imageVersion)) {
         v.visit(ImageElement.TRANSACTION_ID, in.readLong());
       }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageVisitor.java

@@ -38,6 +38,9 @@ abstract class ImageVisitor {
     LAYOUT_VERSION,
     NUM_INODES,
     GENERATION_STAMP,
+    GENERATION_STAMP_V2,
+    GENERATION_STAMP_V1_LIMIT,
+    LAST_ALLOCATED_BLOCK_ID,
     INODES,
     INODE,
     INODE_PATH,

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

@@ -241,6 +241,39 @@ public class DFSTestUtil {
       IOUtils.closeStream(out);
     }
   }
+
+  public static void createFile(FileSystem fs, Path fileName, int bufferLen,
+                                long fileLen, long blockSize, short replFactor, long seed)
+      throws IOException {
+    assert bufferLen > 0;
+    if (!fs.mkdirs(fileName.getParent())) {
+      throw new IOException("Mkdirs failed to create " +
+                            fileName.getParent().toString());
+    }
+    FSDataOutputStream out = null;
+    try {
+      out = fs.create(fileName, true, fs.getConf()
+                                        .getInt(CommonConfigurationKeys.IO_FILE_BUFFER_SIZE_KEY, 4096),
+                      replFactor, blockSize);
+      if (fileLen > 0) {
+        byte[] toWrite = new byte[bufferLen];
+        Random rb = new Random(seed);
+        long bytesToWrite = fileLen;
+        while (bytesToWrite>0) {
+          rb.nextBytes(toWrite);
+          int bytesToWriteNext = (bufferLen < bytesToWrite) ? bufferLen
+              : (int) bytesToWrite;
+
+          out.write(toWrite, 0, bytesToWriteNext);
+          bytesToWrite -= bytesToWriteNext;
+        }
+      }
+    } finally {
+      if (out != null) {
+        out.close();
+      }
+    }
+  }
   
   /** check if the files have been copied correctly. */
   public boolean checkFiles(FileSystem fs, String topdir) throws IOException {
@@ -554,7 +587,7 @@ public class DFSTestUtil {
   }
   
   public static ExtendedBlock getFirstBlock(FileSystem fs, Path path) throws IOException {
-    HdfsDataInputStream in = (HdfsDataInputStream)((DistributedFileSystem)fs).open(path);
+    HdfsDataInputStream in = (HdfsDataInputStream) fs.open(path);
     in.readByte();
     return in.getCurrentBlock();
   }  
@@ -564,6 +597,12 @@ public class DFSTestUtil {
     return ((HdfsDataInputStream) in).getAllBlocks();
   }
 
+  public static List<LocatedBlock> getAllBlocks(FileSystem fs, Path path)
+      throws IOException {
+    HdfsDataInputStream in = (HdfsDataInputStream) fs.open(path);
+    return in.getAllBlocks();
+  }
+
   public static Token<BlockTokenIdentifier> getBlockToken(
       FSDataOutputStream out) {
     return ((DFSOutputStream) out.getWrappedStream()).getBlockToken();

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

@@ -53,7 +53,9 @@ import com.google.common.base.Joiner;
 */
 public class TestDFSUpgrade {
  
-  private static final int EXPECTED_TXID = 45;
+  // TODO: Avoid hard-coding expected_txid. The test should be more robust.
+  private static final int EXPECTED_TXID = 61;
+
   private static final Log LOG = LogFactory.getLog(TestDFSUpgrade.class.getName());
   private Configuration conf;
   private int testCounter = 0;

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

@@ -210,6 +210,7 @@ public class TestDataTransferProtocol {
   @Test 
   public void testOpWrite() throws IOException {
     int numDataNodes = 1;
+    final long BLOCK_ID_FUDGE = 128;
     Configuration conf = new HdfsConfiguration();
     MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).numDataNodes(numDataNodes).build();
     try {
@@ -260,8 +261,9 @@ public class TestDataTransferProtocol {
           "Recover failed close to a finalized replica", false);
       firstBlock.setGenerationStamp(newGS);
 
-      /* Test writing to a new block */
-      long newBlockId = firstBlock.getBlockId() + 1;
+      // Test writing to a new block. Don't choose the next sequential
+      // block ID to avoid conflicting with IDs chosen by the NN.
+      long newBlockId = firstBlock.getBlockId() + BLOCK_ID_FUDGE;
       ExtendedBlock newBlock = new ExtendedBlock(firstBlock.getBlockPoolId(),
           newBlockId, 0, firstBlock.getGenerationStamp());
 
@@ -292,7 +294,7 @@ public class TestDataTransferProtocol {
       Path file1 = new Path("dataprotocol1.dat");    
       DFSTestUtil.createFile(fileSys, file1, 1L, (short)numDataNodes, 0L);
       DFSOutputStream out = (DFSOutputStream)(fileSys.append(file1).
-          getWrappedStream()); 
+          getWrappedStream());
       out.write(1);
       out.hflush();
       FSDataInputStream in = fileSys.open(file1);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/OfflineEditsViewerHelper.java

@@ -64,9 +64,6 @@ public class OfflineEditsViewerHelper {
 
   /**
    * Generates edits with all op codes and returns the edits filename
-   *
-   * @param dfsDir DFS directory (where to setup MiniDFS cluster)
-   * @param editsFilename where to copy the edits
    */
   public String generateEdits() throws IOException {
     CheckpointSignature signature = runOperations();
@@ -142,7 +139,7 @@ public class OfflineEditsViewerHelper {
     DistributedFileSystem dfs =
       (DistributedFileSystem)cluster.getFileSystem();
     FileContext fc = FileContext.getFileContext(cluster.getURI(0), config);
-    // OP_ADD 0, OP_SET_GENSTAMP 10
+    // OP_ADD 0
     Path pathFileCreate = new Path("/file_create_u\1F431");
     FSDataOutputStream s = dfs.create(pathFileCreate);
     // OP_CLOSE 9

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestCheckpoint.java

@@ -1171,7 +1171,8 @@ public class TestCheckpoint {
         throw new IOException(e);
       }
       
-      final int EXPECTED_TXNS_FIRST_SEG = 11;
+      // TODO: Fix the test to not require a hard-coded transaction count.
+      final int EXPECTED_TXNS_FIRST_SEG = 13;
       
       // the following steps should have happened:
       //   edits_inprogress_1 -> edits_1-12  (finalized)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLog.java

@@ -1083,7 +1083,7 @@ public class TestEditLog {
     editlog.initJournalsForWrite();
     editlog.openForWrite();
     for (int i = 2; i < TXNS_PER_ROLL; i++) {
-      editlog.logGenerationStamp((long)0);
+      editlog.logGenerationStampV2((long) 0);
     }
     editlog.logSync();
     
@@ -1095,7 +1095,7 @@ public class TestEditLog {
     for (int i = 0; i < numrolls; i++) {
       editlog.rollEditLog();
       
-      editlog.logGenerationStamp((long)i);
+      editlog.logGenerationStampV2((long) i);
       editlog.logSync();
 
       while (aborts.size() > 0 
@@ -1105,7 +1105,7 @@ public class TestEditLog {
       } 
       
       for (int j = 3; j < TXNS_PER_ROLL; j++) {
-        editlog.logGenerationStamp((long)i);
+        editlog.logGenerationStampV2((long) i);
       }
       editlog.logSync();
     }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestEditLogFileInputStream.java

@@ -18,6 +18,7 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import static org.junit.Assert.*;
+import static org.hamcrest.CoreMatchers.is;
 
 import java.io.IOException;
 import java.io.OutputStream;
@@ -51,10 +52,10 @@ public class TestEditLogFileInputStream {
       // Read the edit log and verify that we got all of the data.
       EnumMap<FSEditLogOpCodes, Holder<Integer>> counts =
           FSImageTestUtil.countEditLogOpTypes(elis);
-      assertEquals(1L, (long)counts.get(FSEditLogOpCodes.OP_ADD).held);
-      assertEquals(1L, (long)counts.get(FSEditLogOpCodes.OP_SET_GENSTAMP).held);
-      assertEquals(1L, (long)counts.get(FSEditLogOpCodes.OP_CLOSE).held);
-     
+      assertThat(counts.get(FSEditLogOpCodes.OP_ADD).held, is(1));
+      assertThat(counts.get(FSEditLogOpCodes.OP_SET_GENSTAMP_V1).held, is(1));
+      assertThat(counts.get(FSEditLogOpCodes.OP_CLOSE).held, is(1));
+
       // Check that length header was picked up.
       assertEquals(FAKE_LOG_DATA.length, elis.length());
       elis.close();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSaveNamespace.java

@@ -541,7 +541,7 @@ public class TestSaveNamespace {
     FSNamesystem spyFsn = spy(fsn);
     final FSNamesystem finalFsn = spyFsn;
     DelayAnswer delayer = new GenericTestUtils.DelayAnswer(LOG);
-    doAnswer(delayer).when(spyFsn).getGenerationStamp();
+    doAnswer(delayer).when(spyFsn).getGenerationStampV2();
     
     ExecutorService pool = Executors.newFixedThreadPool(2);
     

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSequentialBlockId.java

@@ -0,0 +1,209 @@
+/**
+ * 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.hdfs.server.namenode;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.util.List;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DFSTestUtil;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.DatanodeID;
+import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.util.DataChecksum;
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+/**
+ * Tests the sequential block ID generation mechanism and block ID
+ * collision handling.
+ */
+public class TestSequentialBlockId {
+
+  private static final Log LOG = LogFactory.getLog("TestSequentialBlockId");
+
+  private static final DataChecksum DEFAULT_CHECKSUM =
+      DataChecksum.newDataChecksum(DataChecksum.Type.CRC32C, 512);
+
+  final int BLOCK_SIZE = 1024;
+  final int IO_SIZE = BLOCK_SIZE;
+  final short REPLICATION = 1;
+  final long SEED = 0;
+
+  DatanodeID datanode;
+  InetSocketAddress dnAddr;
+
+  /**
+   * Test that block IDs are generated sequentially.
+   *
+   * @throws IOException
+   */
+  @Test
+  public void testBlockIdGeneration() throws IOException {
+    Configuration conf = new HdfsConfiguration();
+    conf.setInt(DFSConfigKeys.DFS_REPLICATION_KEY, 1);
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+
+    try {
+      cluster.waitActive();
+      FileSystem fs = cluster.getFileSystem();
+
+      // Create a file that is 10 blocks long.
+      Path path = new Path("testBlockIdGeneration.dat");
+      DFSTestUtil.createFile(
+          fs, path, IO_SIZE, BLOCK_SIZE * 10, BLOCK_SIZE, REPLICATION, SEED);
+      List<LocatedBlock> blocks = DFSTestUtil.getAllBlocks(fs, path);
+      LOG.info("Block0 id is " + blocks.get(0).getBlock().getBlockId());
+      long nextBlockExpectedId = blocks.get(0).getBlock().getBlockId() + 1;
+
+      // Ensure that the block IDs are sequentially increasing.
+      for (int i = 1; i < blocks.size(); ++i) {
+        long nextBlockId = blocks.get(i).getBlock().getBlockId();
+        LOG.info("Block" + i + " id is " + nextBlockId);
+        assertThat(nextBlockId, is(nextBlockExpectedId));
+        ++nextBlockExpectedId;
+      }
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
+  /**
+   * Test that collisions in the block ID space are handled gracefully.
+   *
+   * @throws IOException
+   */
+  @Test
+  public void testTriggerBlockIdCollision() throws IOException {
+    Configuration conf = new HdfsConfiguration();
+    conf.setInt(DFSConfigKeys.DFS_REPLICATION_KEY, 1);
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+
+    try {
+      cluster.waitActive();
+      FileSystem fs = cluster.getFileSystem();
+      FSNamesystem fsn = cluster.getNamesystem();
+      final int blockCount = 10;
+
+
+      // Create a file with a few blocks to rev up the global block ID
+      // counter.
+      Path path1 = new Path("testBlockIdCollisionDetection_file1.dat");
+      DFSTestUtil.createFile(
+          fs, path1, IO_SIZE, BLOCK_SIZE * blockCount,
+          BLOCK_SIZE, REPLICATION, SEED);
+      List<LocatedBlock> blocks1 = DFSTestUtil.getAllBlocks(fs, path1);
+
+
+      // Rewind the block ID counter in the name system object. This will result
+      // in block ID collisions when we try to allocate new blocks.
+      SequentialBlockIdGenerator blockIdGenerator = fsn.getBlockIdGenerator();
+      blockIdGenerator.setCurrentValue(blockIdGenerator.getCurrentValue() - 5);
+
+      // Trigger collisions by creating a new file.
+      Path path2 = new Path("testBlockIdCollisionDetection_file2.dat");
+      DFSTestUtil.createFile(
+          fs, path2, IO_SIZE, BLOCK_SIZE * blockCount,
+          BLOCK_SIZE, REPLICATION, SEED);
+      List<LocatedBlock> blocks2 = DFSTestUtil.getAllBlocks(fs, path2);
+      assertThat(blocks2.size(), is(blockCount));
+
+      // Make sure that file2 block IDs start immediately after file1
+      assertThat(blocks2.get(0).getBlock().getBlockId(),
+                 is(blocks1.get(9).getBlock().getBlockId() + 1));
+
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
+  /**
+   * Test that the block type (legacy or not) can be correctly detected
+   * based on its generation stamp.
+   *
+   * @throws IOException
+   */
+  @Test
+  public void testBlockTypeDetection() throws IOException {
+
+    // Setup a mock object and stub out a few routines to
+    // retrieve the generation stamp counters.
+    FSNamesystem fsn = mock(FSNamesystem.class);
+    final long maxGenStampForLegacyBlocks = 10000;
+
+    when(fsn.getGenerationStampV1Limit())
+        .thenReturn(maxGenStampForLegacyBlocks);
+
+    Block legacyBlock = spy(new Block());
+    when(legacyBlock.getGenerationStamp())
+        .thenReturn(maxGenStampForLegacyBlocks/2);
+
+    Block newBlock = spy(new Block());
+    when(newBlock.getGenerationStamp())
+        .thenReturn(maxGenStampForLegacyBlocks+1);
+
+    // Make sure that isLegacyBlock() can correctly detect
+    // legacy and new blocks.
+    when(fsn.isLegacyBlock(any(Block.class))).thenCallRealMethod();
+    assertThat(fsn.isLegacyBlock(legacyBlock), is(true));
+    assertThat(fsn.isLegacyBlock(newBlock), is(false));
+  }
+
+  /**
+   * Test that the generation stamp for legacy and new blocks is updated
+   * as expected.
+   *
+   * @throws IOException
+   */
+  @Test
+  public void testGenerationStampUpdate() throws IOException {
+
+    // Setup a mock object and stub out a few routines to
+    // retrieve the generation stamp counters.
+    FSNamesystem fsn = mock(FSNamesystem.class);
+    FSEditLog editLog = mock(FSEditLog.class);
+    final long nextGenerationStampV1 = 5000;
+    final long nextGenerationStampV2 = 20000;
+
+    when(fsn.getNextGenerationStampV1())
+        .thenReturn(nextGenerationStampV1);
+    when(fsn.getNextGenerationStampV2())
+        .thenReturn(nextGenerationStampV2);
+
+    // Make sure that the generation stamp is set correctly for both
+    // kinds of blocks.
+    when(fsn.nextGenerationStamp(anyBoolean())).thenCallRealMethod();
+    when(fsn.hasWriteLock()).thenReturn(true);
+    when(fsn.getEditLog()).thenReturn(editLog);
+    assertThat(fsn.nextGenerationStamp(true), is(nextGenerationStampV1));
+    assertThat(fsn.nextGenerationStamp(false), is(nextGenerationStampV2));
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/TestOfflineEditsViewer.java

@@ -44,7 +44,13 @@ public class TestOfflineEditsViewer {
   private static final Map<FSEditLogOpCodes, Boolean> obsoleteOpCodes =
     new HashMap<FSEditLogOpCodes, Boolean>();
 
-  static { initializeObsoleteOpCodes(); }
+  private static final Map<FSEditLogOpCodes, Boolean> missingOpCodes =
+      new HashMap<FSEditLogOpCodes, Boolean>();
+
+  static {
+    initializeObsoleteOpCodes();
+    initializeMissingOpCodes();
+  }
 
   private static String buildDir =
     System.getProperty("test.build.data", "build/test/data");
@@ -74,6 +80,16 @@ public class TestOfflineEditsViewer {
     obsoleteOpCodes.put(FSEditLogOpCodes.OP_CLEAR_NS_QUOTA, true);
   }
 
+  /**
+   * Initialize missingOpcodes
+   *
+   *  Opcodes that are not available except after uprade from
+   *  an older version. We don't test these here.
+   */
+  private static void initializeMissingOpCodes() {
+    obsoleteOpCodes.put(FSEditLogOpCodes.OP_SET_GENSTAMP_V1, true);
+  }
+
   @Before
   public void setup() {
     new File(cacheDir).mkdirs();
@@ -103,6 +119,8 @@ public class TestOfflineEditsViewer {
     assertTrue(
       "Edits " + edits + " should have all op codes",
       hasAllOpCodes(edits));
+    LOG.info("Comparing generated file " + editsReparsed +
+             " with reference file " + edits);
     assertTrue(
       "Generated edits and reparsed (bin to XML to bin) should be same",
       filesEqualIgnoreTrailingZeros(edits, editsReparsed));
@@ -222,9 +240,12 @@ public class TestOfflineEditsViewer {
       // don't need to test obsolete opCodes
       if(obsoleteOpCodes.containsKey(opCode)) {
         continue;
-      }
-      if (opCode == FSEditLogOpCodes.OP_INVALID)
+      } else if (missingOpCodes.containsKey(opCode)) {
+        continue;
+      } else if (opCode == FSEditLogOpCodes.OP_INVALID) {
         continue;
+      }
+
       Long count = visitor.getStatistics().get(opCode);
       if((count == null) || (count == 0)) {
         hasAllOpCodes = false;