HADOOP-12327. Initialize output buffers with ZERO bytes in erasure coder. Contributed by Kai Zheng.

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -603,6 +603,9 @@ Trunk (Unreleased)
 
       HADOOP-11921. Enhance tests for erasure coders. (Kai Zheng)
 
+      HADOOP-12327. Initialize output buffers with ZERO bytes in erasure coder.
+      (Kai Zheng via waltersu4549)
+
 Release 2.8.0 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java

@@ -32,6 +32,7 @@ import java.nio.ByteBuffer;
 public abstract class AbstractRawErasureCoder
     extends Configured implements RawErasureCoder {
 
+  private static byte[] emptyChunk = new byte[4096];
   private final int numDataUnits;
   private final int numParityUnits;
   private final int numAllUnits;
@@ -42,6 +43,23 @@ public abstract class AbstractRawErasureCoder
     this.numAllUnits = numDataUnits + numParityUnits;
   }
 
+  /**
+   * Make sure to return an empty chunk buffer for the desired length.
+   * @param leastLength
+   * @return empty chunk of zero bytes
+   */
+  protected static byte[] getEmptyChunk(int leastLength) {
+    if (emptyChunk.length >= leastLength) {
+      return emptyChunk; // In most time
+    }
+
+    synchronized (AbstractRawErasureCoder.class) {
+      emptyChunk = new byte[leastLength];
+    }
+
+    return emptyChunk;
+  }
+
   @Override
   public int getNumDataUnits() {
     return numDataUnits;
@@ -73,11 +91,9 @@ public abstract class AbstractRawErasureCoder
    * @return the buffer itself, with ZERO bytes written, the position and limit
    *         are not changed after the call
    */
-  protected ByteBuffer resetBuffer(ByteBuffer buffer) {
+  protected ByteBuffer resetBuffer(ByteBuffer buffer, int len) {
     int pos = buffer.position();
-    for (int i = pos; i < buffer.limit(); ++i) {
-      buffer.put((byte) 0);
-    }
+    buffer.put(getEmptyChunk(len), 0, len);
     buffer.position(pos);
 
     return buffer;
@@ -90,9 +106,8 @@ public abstract class AbstractRawErasureCoder
    * @return the buffer itself
    */
   protected byte[] resetBuffer(byte[] buffer, int offset, int len) {
-    for (int i = offset; i < len; ++i) {
-      buffer[i] = (byte) 0;
-    }
+    byte[] empty = getEmptyChunk(len);
+    System.arraycopy(empty, 0, buffer, offset, len);
 
     return buffer;
   }
@@ -104,9 +119,10 @@ public abstract class AbstractRawErasureCoder
    * @param allowNull whether to allow any element to be null or not
    * @param dataLen the length of data available in the buffer to ensure with
    * @param isDirectBuffer is direct buffer or not to ensure with
+   * @param isOutputs is output buffer or not
    */
-  protected void ensureLengthAndType(ByteBuffer[] buffers, boolean allowNull,
-                                     int dataLen, boolean isDirectBuffer) {
+  protected void checkParameterBuffers(ByteBuffer[] buffers, boolean
+      allowNull, int dataLen, boolean isDirectBuffer, boolean isOutputs) {
     for (ByteBuffer buffer : buffers) {
       if (buffer == null && !allowNull) {
         throw new HadoopIllegalArgumentException(
@@ -120,18 +136,23 @@ public abstract class AbstractRawErasureCoder
           throw new HadoopIllegalArgumentException(
               "Invalid buffer, isDirect should be " + isDirectBuffer);
         }
+        if (isOutputs) {
+          resetBuffer(buffer, dataLen);
+        }
       }
     }
   }
 
   /**
-   * Check and ensure the buffers are of the length specified by dataLen.
+   * Check and ensure the buffers are of the length specified by dataLen. If is
+   * output buffers, ensure they will be ZEROed.
    * @param buffers the buffers to check
    * @param allowNull whether to allow any element to be null or not
    * @param dataLen the length of data available in the buffer to ensure with
+   * @param isOutputs is output buffer or not
    */
-  protected void ensureLength(byte[][] buffers,
-                              boolean allowNull, int dataLen) {
+  protected void checkParameterBuffers(byte[][] buffers, boolean allowNull,
+                                       int dataLen, boolean isOutputs) {
     for (byte[] buffer : buffers) {
       if (buffer == null && !allowNull) {
         throw new HadoopIllegalArgumentException(
@@ -139,6 +160,8 @@ public abstract class AbstractRawErasureCoder
       } else if (buffer != null && buffer.length != dataLen) {
         throw new HadoopIllegalArgumentException(
             "Invalid buffer not of length " + dataLen);
+      } else if (isOutputs) {
+        resetBuffer(buffer, 0, dataLen);
       }
     }
   }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java

@@ -48,8 +48,8 @@ public abstract class AbstractRawErasureDecoder extends AbstractRawErasureCoder
     if (dataLen == 0) {
       return;
     }
-    ensureLengthAndType(inputs, true, dataLen, usingDirectBuffer);
-    ensureLengthAndType(outputs, false, dataLen, usingDirectBuffer);
+    checkParameterBuffers(inputs, true, dataLen, usingDirectBuffer, false);
+    checkParameterBuffers(outputs, false, dataLen, usingDirectBuffer, true);
 
     if (usingDirectBuffer) {
       doDecode(inputs, erasedIndexes, outputs);
@@ -106,8 +106,8 @@ public abstract class AbstractRawErasureDecoder extends AbstractRawErasureCoder
     if (dataLen == 0) {
       return;
     }
-    ensureLength(inputs, true, dataLen);
-    ensureLength(outputs, false, dataLen);
+    checkParameterBuffers(inputs, true, dataLen, false);
+    checkParameterBuffers(outputs, false, dataLen, true);
 
     int[] inputOffsets = new int[inputs.length]; // ALL ZERO
     int[] outputOffsets = new int[outputs.length]; // ALL ZERO

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java

@@ -45,8 +45,8 @@ public abstract class AbstractRawErasureEncoder extends AbstractRawErasureCoder
     if (dataLen == 0) {
       return;
     }
-    ensureLengthAndType(inputs, false, dataLen, usingDirectBuffer);
-    ensureLengthAndType(outputs, false, dataLen, usingDirectBuffer);
+    checkParameterBuffers(inputs, false, dataLen, usingDirectBuffer, false);
+    checkParameterBuffers(outputs, false, dataLen, usingDirectBuffer, true);
 
     if (usingDirectBuffer) {
       doEncode(inputs, outputs);
@@ -93,8 +93,8 @@ public abstract class AbstractRawErasureEncoder extends AbstractRawErasureCoder
     if (dataLen == 0) {
       return;
     }
-    ensureLength(inputs, false, dataLen);
-    ensureLength(outputs, false, dataLen);
+    checkParameterBuffers(inputs, false, dataLen, false);
+    checkParameterBuffers(outputs, false, dataLen, true);
 
     int[] inputOffsets = new int[inputs.length]; // ALL ZERO
     int[] outputOffsets = new int[outputs.length]; // ALL ZERO

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java

@@ -206,7 +206,7 @@ public class RSRawDecoder extends AbstractRawErasureDecoder {
         if (erasedIndexes[i] == erasedOrNotToReadIndexes[j]) {
           found = true;
           adjustedDirectBufferOutputsParameter[j] =
-              resetBuffer(outputs[outputIdx++]);
+              resetBuffer(outputs[outputIdx++], dataLen);
         }
       }
       if (!found) {
@@ -220,7 +220,7 @@ public class RSRawDecoder extends AbstractRawErasureDecoder {
         ByteBuffer buffer = checkGetDirectBuffer(bufferIdx, dataLen);
         buffer.position(0);
         buffer.limit(dataLen);
-        adjustedDirectBufferOutputsParameter[i] = resetBuffer(buffer);
+        adjustedDirectBufferOutputsParameter[i] = resetBuffer(buffer, dataLen);
         bufferIdx++;
       }
     }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java

@@ -39,7 +39,6 @@ public class XORRawDecoder extends AbstractRawErasureDecoder {
   protected void doDecode(ByteBuffer[] inputs, int[] erasedIndexes,
                           ByteBuffer[] outputs) {
     ByteBuffer output = outputs[0];
-    resetBuffer(output);
 
     int erasedIdx = erasedIndexes[0];
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java

@@ -37,7 +37,6 @@ public class XORRawEncoder extends AbstractRawErasureEncoder {
 
   protected void doEncode(ByteBuffer[] inputs, ByteBuffer[] outputs) {
     ByteBuffer output = outputs[0];
-    resetBuffer(output);
 
     // Get the first buffer's data.
     int iIdx, oIdx;

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSStripedOutputStream.java

@@ -221,9 +221,6 @@ public class DFSStripedOutputStream extends DFSOutputStream {
     private void clear() {
       for (int i = 0; i< numAllBlocks; i++) {
         buffers[i].clear();
-        if (i >= numDataBlocks) {
-          Arrays.fill(buffers[i].array(), (byte) 0);
-        }
       }
     }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/ErasureCodingWorker.java

@@ -907,15 +907,10 @@ public final class ErasureCodingWorker {
 
       for (int i = 0; i < targetBuffers.length; i++) {
         if (targetBuffers[i] != null) {
-          cleanBuffer(targetBuffers[i]);
+          targetBuffers[i].clear();
         }
       }
     }
-    
-    private ByteBuffer cleanBuffer(ByteBuffer buffer) {
-      Arrays.fill(buffer.array(), (byte) 0);
-      return (ByteBuffer)buffer.clear();
-    }
 
     // send an empty packet to mark the end of the block
     private void endTargetBlocks(boolean[] targetsStatus) {