HDFS-8081. Split getAdditionalBlock() into two methods. Contributed by Konstantin Shvachko

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

@@ -474,6 +474,8 @@ Release 2.7.1 - UNRELEASED
 
   IMPROVEMENTS
 
+    HDFS-8081. Split getAdditionalBlock() into two methods. (shv)
+
   OPTIMIZATIONS
 
   BUG FIXES

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

@@ -3009,6 +3009,31 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
   LocatedBlock getAdditionalBlock(String src, long fileId, String clientName,
       ExtendedBlock previous, Set<Node> excludedNodes, 
       List<String> favoredNodes) throws IOException {
+    LocatedBlock[] onRetryBlock = new LocatedBlock[1];
+    DatanodeStorageInfo targets[] = getNewBlockTargets(src, fileId,
+        clientName, previous, excludedNodes, favoredNodes, onRetryBlock);
+    if (targets == null) {
+      assert onRetryBlock[0] != null : "Retry block is null";
+      // This is a retry. Just return the last block.
+      return onRetryBlock[0];
+    }
+    LocatedBlock newBlock = storeAllocatedBlock(
+        src, fileId, clientName, previous, targets);
+    return newBlock;
+  }
+
+  /**
+   * Part I of getAdditionalBlock().
+   * Analyze the state of the file under read lock to determine if the client
+   * can add a new block, detect potential retries, lease mismatches,
+   * and minimal replication of the penultimate block.
+   * 
+   * Generate target DataNode locations for the new block,
+   * but do not create the new block yet.
+   */
+  DatanodeStorageInfo[] getNewBlockTargets(String src, long fileId,
+      String clientName, ExtendedBlock previous, Set<Node> excludedNodes,
+      List<String> favoredNodes, LocatedBlock[] onRetryBlock) throws IOException {
     final long blockSize;
     final int replication;
     final byte storagePolicyID;
@@ -3020,7 +3045,6 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
           + src + " inodeId " +  fileId  + " for " + clientName);
     }
 
-    // Part I. Analyze the state of the file with respect to the input data.
     checkOperation(OperationCategory.READ);
     byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(src);
     FSPermissionChecker pc = getPermissionChecker();
@@ -3028,7 +3052,6 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     try {
       checkOperation(OperationCategory.READ);
       src = dir.resolvePath(pc, src, pathComponents);
-      LocatedBlock[] onRetryBlock = new LocatedBlock[1];
       FileState fileState = analyzeFileState(
           src, fileId, clientName, previous, onRetryBlock);
       final INodeFile pendingFile = fileState.inode;
@@ -3039,8 +3062,9 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
       src = fileState.path;
 
       if (onRetryBlock[0] != null && onRetryBlock[0].getLocations().length > 0) {
-        // This is a retry. Just return the last block if having locations.
-        return onRetryBlock[0];
+        // This is a retry. No need to generate new locations.
+        // Use the last block if it has locations.
+        return null;
       }
       if (pendingFile.getBlocks().length >= maxBlocksPerFile) {
         throw new IOException("File has reached the limit on maximum number of"
@@ -3064,12 +3088,20 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     }
 
     // choose targets for the new block to be allocated.
-    final DatanodeStorageInfo targets[] = getBlockManager().chooseTarget4NewBlock( 
+    return getBlockManager().chooseTarget4NewBlock( 
         src, replication, clientNode, excludedNodes, blockSize, favoredNodes,
         storagePolicyID);
+  }
 
-    // Part II.
-    // Allocate a new block, add it to the INode and the BlocksMap. 
+  /**
+   * Part II of getAdditionalBlock().
+   * Should repeat the same analysis of the file state as in Part 1,
+   * but under the write lock.
+   * If the conditions still hold, then allocate a new block with
+   * the new targets, add it to the INode and to the BlocksMap.
+   */
+  LocatedBlock storeAllocatedBlock(String src, long fileId, String clientName,
+      ExtendedBlock previous, DatanodeStorageInfo[] targets) throws IOException {
     Block newBlock = null;
     long offset;
     checkOperation(OperationCategory.WRITE);

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

@@ -20,16 +20,10 @@ package org.apache.hadoop.hdfs.server.namenode;
 
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.doAnswer;
-import static org.mockito.Mockito.spy;
-
 import java.io.IOException;
-import java.lang.reflect.Field;
 import java.util.EnumSet;
-import java.util.HashSet;
-import java.util.List;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
@@ -38,18 +32,12 @@ import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
-import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
-import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
 import org.apache.hadoop.io.EnumSetWritable;
-import org.apache.hadoop.net.Node;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
-import org.mockito.Mockito;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.stubbing.Answer;
 
 /**
  * Race between two threads simultaneously calling
@@ -63,10 +51,6 @@ public class TestAddBlockRetry {
   private Configuration conf;
   private MiniDFSCluster cluster;
 
-  private int count = 0;
-  private LocatedBlock lb1;
-  private LocatedBlock lb2;
-
   @Before
   public void setUp() throws Exception {
     conf = new Configuration();
@@ -92,43 +76,8 @@ public class TestAddBlockRetry {
     final String src = "/testRetryAddBlockWhileInChooseTarget";
 
     final FSNamesystem ns = cluster.getNamesystem();
-    BlockManager spyBM = spy(ns.getBlockManager());
     final NamenodeProtocols nn = cluster.getNameNodeRpc();
 
-    // substitute mocked BlockManager into FSNamesystem
-    Class<? extends FSNamesystem> nsClass = ns.getClass();
-    Field bmField = nsClass.getDeclaredField("blockManager");
-    bmField.setAccessible(true);
-    bmField.set(ns, spyBM);
-
-    doAnswer(new Answer<DatanodeStorageInfo[]>() {
-      @Override
-      public DatanodeStorageInfo[] answer(InvocationOnMock invocation)
-          throws Throwable {
-        LOG.info("chooseTarget for " + src);
-        DatanodeStorageInfo[] ret =
-            (DatanodeStorageInfo[]) invocation.callRealMethod();
-        assertTrue("Penultimate block must be complete",
-            checkFileProgress(src, false));
-        count++;
-        if(count == 1) { // run second addBlock()
-          LOG.info("Starting second addBlock for " + src);
-          nn.addBlock(src, "clientName", null, null,
-              INodeId.GRANDFATHER_INODE_ID, null);
-          assertTrue("Penultimate block must be complete",
-              checkFileProgress(src, false));
-          LocatedBlocks lbs = nn.getBlockLocations(src, 0, Long.MAX_VALUE);
-          assertEquals("Must be one block", 1, lbs.getLocatedBlocks().size());
-          lb2 = lbs.get(0);
-          assertEquals("Wrong replication",
-              REPLICATION, lb2.getLocations().length);
-        }
-        return ret;
-      }
-    }).when(spyBM).chooseTarget4NewBlock(Mockito.anyString(), Mockito.anyInt(),
-        Mockito.<DatanodeDescriptor>any(), Mockito.<HashSet<Node>>any(),
-        Mockito.anyLong(), Mockito.<List<String>>any(), Mockito.anyByte());
-
     // create file
     nn.create(src, FsPermission.getFileDefault(),
         "clientName",
@@ -137,12 +86,32 @@ public class TestAddBlockRetry {
 
     // start first addBlock()
     LOG.info("Starting first addBlock for " + src);
-    nn.addBlock(src, "clientName", null, null, INodeId.GRANDFATHER_INODE_ID, null);
+    LocatedBlock[] onRetryBlock = new LocatedBlock[1];
+    DatanodeStorageInfo targets[] = ns.getNewBlockTargets(
+        src, INodeId.GRANDFATHER_INODE_ID, "clientName",
+        null, null, null, onRetryBlock);
+    assertNotNull("Targets must be generated", targets);
 
-    // check locations
+    // run second addBlock()
+    LOG.info("Starting second addBlock for " + src);
+    nn.addBlock(src, "clientName", null, null,
+        INodeId.GRANDFATHER_INODE_ID, null);
+    assertTrue("Penultimate block must be complete",
+        checkFileProgress(src, false));
     LocatedBlocks lbs = nn.getBlockLocations(src, 0, Long.MAX_VALUE);
     assertEquals("Must be one block", 1, lbs.getLocatedBlocks().size());
-    lb1 = lbs.get(0);
+    LocatedBlock lb2 = lbs.get(0);
+    assertEquals("Wrong replication", REPLICATION, lb2.getLocations().length);
+
+    // continue first addBlock()
+    LocatedBlock newBlock = ns.storeAllocatedBlock(
+        src, INodeId.GRANDFATHER_INODE_ID, "clientName", null, targets);
+    assertEquals("Blocks are not equal", lb2.getBlock(), newBlock.getBlock());
+
+    // check locations
+    lbs = nn.getBlockLocations(src, 0, Long.MAX_VALUE);
+    assertEquals("Must be one block", 1, lbs.getLocatedBlocks().size());
+    LocatedBlock lb1 = lbs.get(0);
     assertEquals("Wrong replication", REPLICATION, lb1.getLocations().length);
     assertEquals("Blocks are not equal", lb1.getBlock(), lb2.getBlock());
   }