HDFS-14440. RBF: Optimize the file write process in case of multiple destinations. Contributed by Ayush Saxena.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java

@@ -631,28 +631,11 @@ RemoteLocation getCreateLocation(
     RemoteLocation createLocation = locations.get(0);
     if (locations.size() > 1) {
       try {
-        // Check if this file already exists in other subclusters
+        RemoteLocation existingLocation = getExistingLocation(src, locations);
-        LocatedBlocks existingLocation = getBlockLocations(src, 0, 1);
-        if (existingLocation != null) {
         // Forward to the existing location and let the NN handle the error
-          LocatedBlock existingLocationLastLocatedBlock =
+        if (existingLocation != null) {
-              existingLocation.getLastLocatedBlock();
+          LOG.debug("{} already exists in {}.", src, existingLocation);
-          if (existingLocationLastLocatedBlock == null) {
+          createLocation = existingLocation;
-            // The block has no blocks yet, check for the meta data
-            for (RemoteLocation location : locations) {
-              RemoteMethod method = new RemoteMethod("getFileInfo",
-                  new Class<?>[] {String.class}, new RemoteParam());
-              if (rpcClient.invokeSingle(location, method) != null) {
-                createLocation = location;
-                break;
-              }
-            }
-          } else {
-            ExtendedBlock existingLocationLastBlock =
-                existingLocationLastLocatedBlock.getBlock();
-            String blockPoolId = existingLocationLastBlock.getBlockPoolId();
-            createLocation = getLocationForPath(src, true, blockPoolId);
-          }
         }
       } catch (FileNotFoundException fne) {
         // Ignore if the file is not found
@@ -661,6 +644,27 @@ RemoteLocation getCreateLocation(
     return createLocation;
   }
 
+  /**
+   * Gets the remote location where the file exists.
+   * @param src the name of file.
+   * @param locations all the remote locations.
+   * @return the remote location of the file if it exists, else null.
+   * @throws IOException in case of any exception.
+   */
+  private RemoteLocation getExistingLocation(String src,
+      List<RemoteLocation> locations) throws IOException {
+    RemoteMethod method = new RemoteMethod("getFileInfo",
+        new Class<?>[] {String.class}, new RemoteParam());
+    Map<RemoteLocation, HdfsFileStatus> results = rpcClient.invokeConcurrent(
+        locations, method, false, false, HdfsFileStatus.class);
+    for (RemoteLocation loc : locations) {
+      if (results.get(loc) != null) {
+        return loc;
+      }
+    }
+    return null;
+  }
+
   @Override // ClientProtocol
   public LastBlockWithStatus append(String src, final String clientName,
       final EnumSetWritable<CreateFlag> flag) throws IOException {