HDFS-8499. Refactor BlockInfo class hierarchy with static helper class. Contributed by Zhe Zhang.

Author: umbrant

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

@@ -626,6 +626,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-7923. The DataNodes should rate-limit their full block reports by
     asking the NN on heartbeat messages (cmccabe)
 
+    HDFS-8499. Refactor BlockInfo class hierarchy with static helper class.
+    (Zhe Zhang via wang)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

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

@@ -79,7 +79,7 @@ public interface BlockCollection {
    * Convert the last block of the collection to an under-construction block
    * and set the locations.
    */
-  public BlockInfoContiguousUnderConstruction setLastBlock(BlockInfo lastBlock,
+  public BlockInfoUnderConstruction setLastBlock(BlockInfo lastBlock,
       DatanodeStorageInfo[] targets) throws IOException;
 
   /**

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

@@ -51,7 +51,7 @@ public abstract class  BlockInfo extends Block
    * per replica is 42 bytes (LinkedList#Entry object per replica) versus 16
    * bytes using the triplets.
    */
-  protected Object[] triplets;
+  Object[] triplets;
 
   /**
    * Construct an entry for blocksmap
@@ -295,7 +295,7 @@ public BlockInfo moveBlockToHead(BlockInfo head,
   /**
    * BlockInfo represents a block that is not being constructed.
    * In order to start modifying the block, the BlockInfo should be converted
-   * to {@link BlockInfoContiguousUnderConstruction}.
+   * to {@link BlockInfoUnderConstruction}.
    * @return {@link BlockUCState#COMPLETE}
    */
   public BlockUCState getBlockUCState() {
@@ -312,27 +312,29 @@ public boolean isComplete() {
   }
 
   /**
-   * Convert a complete block to an under construction block.
+   * Convert a block to an under construction block.
    * @return BlockInfoUnderConstruction -  an under construction block.
    */
-  public BlockInfoContiguousUnderConstruction convertToBlockUnderConstruction(
+  public BlockInfoUnderConstruction convertToBlockUnderConstruction(
       BlockUCState s, DatanodeStorageInfo[] targets) {
     if(isComplete()) {
-      BlockInfoContiguousUnderConstruction ucBlock =
-          new BlockInfoContiguousUnderConstruction(this,
-          getBlockCollection().getPreferredBlockReplication(), s, targets);
-      ucBlock.setBlockCollection(getBlockCollection());
-      return ucBlock;
+      return convertCompleteBlockToUC(s, targets);
     }
     // the block is already under construction
-    BlockInfoContiguousUnderConstruction ucBlock =
-        (BlockInfoContiguousUnderConstruction)this;
+    BlockInfoUnderConstruction ucBlock =
+        (BlockInfoUnderConstruction)this;
     ucBlock.setBlockUCState(s);
     ucBlock.setExpectedLocations(targets);
     ucBlock.setBlockCollection(getBlockCollection());
     return ucBlock;
   }
 
+  /**
+   * Convert a complete block to an under construction block.
+   */
+  abstract BlockInfoUnderConstruction convertCompleteBlockToUC(
+      BlockUCState s, DatanodeStorageInfo[] targets);
+
   @Override
   public int hashCode() {
     // Super implementation is sufficient

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

@@ -19,13 +19,13 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
 
 /**
  * Subclass of {@link BlockInfo}, used for a block with replication scheme.
  */
 @InterfaceAudience.Private
 public class BlockInfoContiguous extends BlockInfo {
-  public static final BlockInfoContiguous[] EMPTY_ARRAY = {};
 
   public BlockInfoContiguous(short size) {
     super(size);
@@ -40,84 +40,37 @@ public BlockInfoContiguous(Block blk, short size) {
    * This is used to convert BlockReplicationInfoUnderConstruction
    * @param from BlockReplicationInfo to copy from.
    */
-  protected BlockInfoContiguous(BlockInfoContiguous from) {
+  protected BlockInfoContiguous(BlockInfo from) {
     super(from);
   }
 
-  /**
-   * Ensure that there is enough  space to include num more triplets.
-   * @return first free triplet index.
-   */
-  private int ensureCapacity(int num) {
-    assert this.triplets != null : "BlockInfo is not initialized";
-    int last = numNodes();
-    if (triplets.length >= (last+num)*3) {
-      return last;
-    }
-    /* Not enough space left. Create a new array. Should normally
-     * happen only when replication is manually increased by the user. */
-    Object[] old = triplets;
-    triplets = new Object[(last+num)*3];
-    System.arraycopy(old, 0, triplets, 0, last * 3);
-    return last;
-  }
-
   @Override
   boolean addStorage(DatanodeStorageInfo storage) {
-    // find the last null node
-    int lastNode = ensureCapacity(1);
-    setStorageInfo(lastNode, storage);
-    setNext(lastNode, null);
-    setPrevious(lastNode, null);
-    return true;
+    return ContiguousBlockStorageOp.addStorage(this, storage);
   }
 
   @Override
   boolean removeStorage(DatanodeStorageInfo storage) {
-    int dnIndex = findStorageInfo(storage);
-    if (dnIndex < 0) { // the node is not found
-      return false;
-    }
-    assert getPrevious(dnIndex) == null && getNext(dnIndex) == null :
-        "Block is still in the list and must be removed first.";
-    // find the last not null node
-    int lastNode = numNodes()-1;
-    // replace current node triplet by the lastNode one
-    setStorageInfo(dnIndex, getStorageInfo(lastNode));
-    setNext(dnIndex, getNext(lastNode));
-    setPrevious(dnIndex, getPrevious(lastNode));
-    // set the last triplet to null
-    setStorageInfo(lastNode, null);
-    setNext(lastNode, null);
-    setPrevious(lastNode, null);
-    return true;
+    return ContiguousBlockStorageOp.removeStorage(this, storage);
   }
 
   @Override
   public int numNodes() {
-    assert this.triplets != null : "BlockInfo is not initialized";
-    assert triplets.length % 3 == 0 : "Malformed BlockInfo";
-
-    for (int idx = getCapacity()-1; idx >= 0; idx--) {
-      if (getDatanode(idx) != null) {
-        return idx + 1;
-      }
-    }
-    return 0;
+    return ContiguousBlockStorageOp.numNodes(this);
   }
 
   @Override
   void replaceBlock(BlockInfo newBlock) {
-    assert newBlock instanceof BlockInfoContiguous;
-    for (int i = this.numNodes() - 1; i >= 0; i--) {
-      final DatanodeStorageInfo storage = this.getStorageInfo(i);
-      final boolean removed = storage.removeBlock(this);
-      assert removed : "currentBlock not found.";
+    ContiguousBlockStorageOp.replaceBlock(this, newBlock);
+  }
 
-      final DatanodeStorageInfo.AddBlockResult result = storage.addBlock(
-          newBlock);
-      assert result == DatanodeStorageInfo.AddBlockResult.ADDED :
-          "newBlock already exists.";
-    }
+  @Override
+  BlockInfoUnderConstruction convertCompleteBlockToUC(
+      HdfsServerConstants.BlockUCState s, DatanodeStorageInfo[] targets) {
+    BlockInfoUnderConstructionContiguous ucBlock =
+        new BlockInfoUnderConstructionContiguous(this,
+            getBlockCollection().getPreferredBlockReplication(), s, targets);
+    ucBlock.setBlockCollection(getBlockCollection());
+    return ucBlock;
   }
 }