[GitHub] [helix] xyuanlu commented on a change in pull request #1645: Use thread pool for batched call back handling events

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

xyuanlu commented on a change in pull request #1645:
URL: https://github.com/apache/helix/pull/1645#discussion_r580648551



##########
File path: helix-core/src/main/java/org/apache/helix/manager/zk/CallbackEventTPFactory.java
##########
@@ -0,0 +1,76 @@
+package org.apache.helix.manager.zk;
+
+
+
+/*
+ * 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.
+ */
+
+// returns a thread pool object given a HelixManager identifier
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+
+
+public class CallbackEventTPFactory {
+  static private final ReadWriteLock _lock = new ReentrantReadWriteLock();
+  static private Map<Integer, ThreadPoolExecutor> _managerToCallBackThreadPoolMap = new HashMap();
+
+  public static ThreadPoolExecutor getThreadPool(int mapHash) {
+    // should not use general lock for read
+    _lock.readLock().lock();
+    ThreadPoolExecutor result;
+    if (_managerToCallBackThreadPoolMap.containsKey(mapHash)) {
+      result = _managerToCallBackThreadPoolMap.get(mapHash);
+      _lock.readLock().unlock();
+    } else {
+      _lock.readLock().unlock();
+      result = getAndCreateThreadPool(mapHash);
+    }
+    return result;
+  }
+
+  public static ThreadPoolExecutor getAndCreateThreadPool(int mapHash) {
+    ThreadPoolExecutor result;
+    _lock.writeLock().lock();
+    // first check if the key is already in the map
+    if (_managerToCallBackThreadPoolMap.containsKey(mapHash)) {
+      // downgrade to read lock
+      _lock.readLock().lock();
+      result = _managerToCallBackThreadPoolMap.get(mapHash);
+      _lock.readLock().unlock();
+    } else {
+      ThreadFactory namedThreadFactory = new ThreadFactoryBuilder()
+          .setNameFormat(String.format("CallbackHandlerExecutorService - %s ", mapHash)).build();
+      result = new ThreadPoolExecutor(5, 5, 1, TimeUnit.SECONDS, new LinkedBlockingQueue<>(),

Review comment:
       TFTR. Updated.

##########
File path: helix-core/src/main/java/org/apache/helix/manager/zk/CallbackEventTPFactory.java
##########
@@ -0,0 +1,76 @@
+package org.apache.helix.manager.zk;
+
+
+
+/*
+ * 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.
+ */
+
+// returns a thread pool object given a HelixManager identifier
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+
+
+public class CallbackEventTPFactory {

Review comment:
       TFTR. The threadpool is one-one mapping to HelixManager, not executor. I think having a factory will provide a layer of abstraction for thread pool creation, so each CallbackEventExecutor don't need to know if the thread pool for the helixManager is already created. CallbackEventExecutor could just call `getOrCreateThreadPool ` in its constructor. 




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