[GitHub] [iotdb] JackieTien97 commented on a change in pull request #2488: Add DirectByteBufferPool for WAL

[GitBox <gi...@apache.org>]

JackieTien97 commented on a change in pull request #2488:
URL: https://github.com/apache/iotdb/pull/2488#discussion_r558017828



##########
File path: server/src/main/java/org/apache/iotdb/db/engine/storagegroup/StorageGroupProcessor.java
##########
@@ -261,6 +268,79 @@ public void setReady(boolean ready) {
   private List<CloseFileListener> customCloseFileListeners = Collections.emptyList();
   private List<FlushListener> customFlushListeners = Collections.emptyList();
 
+  private static final int WAL_BUFFER_SIZE =
+      IoTDBDescriptor.getInstance().getConfig().getWalBufferSize() / 2;
+
+  private static final int MAX_WAL_BYTEBUFFER_NUM =
+      IoTDBDescriptor.getInstance().getConfig().getConcurrentWritingTimePartition() * 4;
+
+  private static final long DEFAULT_POOL_TRIM_INTERVAL_MILLIS = 10_000;
+
+  private final Deque<ByteBuffer> walByteBufferPool = new LinkedList<>();
+
+  private int currentWalPoolSize = 0;
+
+
+  /**
+   * get the direct byte buffer from pool, each fetch contains two ByteBuffer
+   */
+  public ByteBuffer[] getWalDirectByteBuffer() {
+    ByteBuffer[] res = new ByteBuffer[2];
+    synchronized (walByteBufferPool) {
+      while (walByteBufferPool.isEmpty() && currentWalPoolSize + 2 > MAX_WAL_BYTEBUFFER_NUM) {
+        try {
+          walByteBufferPool.wait();
+        } catch (InterruptedException e) {
+          Thread.currentThread().interrupt();
+          logger
+              .error("getDirectByteBuffer occurs error while waiting for DirectByteBuffer"
+                  + "group {}", storageGroupName, e);
+        }
+      }
+      // If the queue is not empty, it must have at least two.
+      if (!walByteBufferPool.isEmpty()) {
+        res[0] = walByteBufferPool.pollFirst();
+        res[1] = walByteBufferPool.pollFirst();
+      } else {
+        // if the queue is empty and current size is less than MAX_BYTEBUFFER_NUM
+        // we can construct another two more new byte buffer
+        currentWalPoolSize += 2;
+        res[0] = ByteBuffer.allocateDirect(WAL_BUFFER_SIZE);
+        res[1] = ByteBuffer.allocateDirect(WAL_BUFFER_SIZE);
+      }
+    }
+    return res;
+  }
+
+  /**
+   * put the byteBuffer back to pool
+   */
+  public void releaseWalBuffer(ByteBuffer[] byteBuffers) {
+    for (ByteBuffer byteBuffer : byteBuffers) {
+      byteBuffer.clear();
+    }
+    synchronized (walByteBufferPool) {
+      walByteBufferPool.addLast(byteBuffers[0]);
+      walByteBufferPool.addLast(byteBuffers[1]);
+      walByteBufferPool.notifyAll();
+    }
+  }
+
+  /**
+   * trim the size of the pool and release the memory of needless direct byte buffer
+   */
+  private void trimTask() {
+    synchronized (walByteBufferPool) {
+      int expectedSize =
+          (workSequenceTsFileProcessors.size() + workUnsequenceTsFileProcessors.size()) * 2;
+      while (expectedSize < currentWalPoolSize && !walByteBufferPool.isEmpty()) {
+        MmapUtil.clean((MappedByteBuffer) walByteBufferPool.removeLast());
+        MmapUtil.clean((MappedByteBuffer) walByteBufferPool.removeLast());
+        currentWalPoolSize -= 2;
+      }
+    }
+  }

Review comment:
       fix

##########
File path: server/src/main/java/org/apache/iotdb/db/utils/MmapUtil.java
##########
@@ -0,0 +1,31 @@
+/*
+ * 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.apache.iotdb.db.utils;
+
+import io.netty.util.internal.PlatformDependent;
+import java.nio.MappedByteBuffer;
+
+public class MmapUtil {
+
+  public static void clean(MappedByteBuffer mappedByteBuffer) {
+    if (mappedByteBuffer == null || !mappedByteBuffer.isDirect() || mappedByteBuffer.capacity()== 0)
+      return;

Review comment:
       fix

##########
File path: server/src/main/java/org/apache/iotdb/db/writelog/node/ExclusiveWriteLogNode.java
##########
@@ -92,6 +90,11 @@ public ExclusiveWriteLogNode(String identifier) {
     }
   }
 
+  public void initBuffer(ByteBuffer[] byteBuffers) {
+    this.logBufferWorking = byteBuffers[0];
+    this.logBufferIdle = byteBuffers[1];
+  }

Review comment:
       fix




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