OPENDJ-3146: DirectByteBuffer lazily freed by the JVM can kill the importer...

Yannick Lecaillez

21.12.2016 d97a7492dd6bae0d765f1284036e2d649a43fb5d

OPENDJ-3146: DirectByteBuffer lazily freed by the JVM can kill the
importer process

Call the DirectByteBuffer's cleaner directly to free the native memory.

 opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/OnDiskMergeImporter.java

@@ -11,7 +11,22 @@
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Portions Copyright 2014 The Apache Software Foundation
 * Copyright 2015-2016 ForgeRock AS.
 * 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.opends.server.backends.pluggable;

@@ -27,6 +42,7 @@
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
@@ -2783,13 +2799,50 @@
    @Override
    public void close()
    {
      boolean allMemoryBufferFreed = true;
      for (final MemoryBuffer memoryBuffer : pool)
      {
        allMemoryBufferFreed &= memoryBuffer.free();
      }
      pool.clear();
      if (!allMemoryBufferFreed)
      {
        // Some DirectByteBuffer were not freed because the cleaner method has failed/is not supported.
        // Do a best effort at freeing these buffers by requesting a GC.
        System.gc();
      }
    }

    /** Buffer wrapping a ByteBuffer. */
    @NotThreadSafe
    static final class MemoryBuffer
    {
      private static final boolean CLEAN_SUPPORTED;
      private static final Method directBufferCleanerMethod;
      private static final Method directBufferCleanerCleanMethod;

      static
      {
        Method tmpDirectBufferCleanerMethod = null;
        Method tmpDirectBufferCleanerCleanMethod = null;
        boolean tmpCleanSupported;
        try
        {
          tmpDirectBufferCleanerMethod = Class.forName("java.nio.DirectByteBuffer").getMethod("cleaner");
          tmpDirectBufferCleanerMethod.setAccessible(true);
          tmpDirectBufferCleanerCleanMethod = Class.forName("sun.misc.Cleaner").getMethod("clean");
          tmpDirectBufferCleanerCleanMethod.setAccessible(true);
          tmpCleanSupported = true;
        }
        catch (Exception e)
        {
          tmpCleanSupported = false;
        }
        CLEAN_SUPPORTED = tmpCleanSupported;
        directBufferCleanerMethod = tmpDirectBufferCleanerMethod;
        directBufferCleanerCleanMethod = tmpDirectBufferCleanerCleanMethod;
      }

      private final ByteBuffer buffer;

      MemoryBuffer(final ByteBuffer byteBuffer)
@@ -2797,6 +2850,34 @@
        this.buffer = byteBuffer;
      }

      boolean free()
      {
        if (!buffer.isDirect())
        {
          // Heap buffers will be GC'd.
          return true;
        }
        if (CLEAN_SUPPORTED)
        {
          try
          {
            /**
             * DirectByteBuffers are garbage collected by using a phantom reference and a reference queue. Every once a
             * while, the JVM checks the reference queue and cleans the DirectByteBuffers. However, as this doesn't
             * happen immediately after discarding all references to a DirectByteBuffer, it's easy to OutOfMemoryError
             * yourself using DirectByteBuffers. Here we explicitly calls the Cleaner method of the DirectByteBuffer.
             */
            directBufferCleanerCleanMethod.invoke(directBufferCleanerMethod.invoke(buffer));
            return true;
          }
          catch (Exception ignored)
          {
            // silently ignore exception
          }
        }
        return false;
      }

      void writeInt(final int position, final int value)
      {
        buffer.putInt(position, value);