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Posted to reviews@helix.apache.org by GitBox <gi...@apache.org> on 2023/01/13 06:09:48 UTC
[GitHub] [helix] jiajunwang commented on a diff in pull request #2338: Implement a thread-safe listener container for zkclient
jiajunwang commented on code in PR #2338:
URL: https://github.com/apache/helix/pull/2338#discussion_r1068951156
##########
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/ListenerContainer.java:
##########
@@ -0,0 +1,186 @@
+package org.apache.helix.zookeeper.zkclient;
+
+/*
+ * 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.
+ */
+
+import com.google.common.annotations.VisibleForTesting;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+
+
+/**
+ * A thread-safe container wrapper class for Listeners registered to ZkClient.
+ * It stores 2 types of listener separately, one-time listener and persistent listener. The former ones are removed
+ * right after its consumption, while the latter need to be explicitly removed.
+ * @param <T> the type of listener
+ */
+public class ListenerContainer<T> {
+ private final ReentrantLock _lock = new ReentrantLock(true);
+ private final Map<String, Set<T>> _persistentListener = new ConcurrentHashMap<>();
+ private final Map<String, Set<T>> _onetimeListener = new ConcurrentHashMap<>();
+
+ /**
+ * Add listener to the container with specified key.
+ * @param key the key to register to
+ * @param listener the listener to register
+ * @param persistListener true if the listener is persistent
+ */
+ public void addListener(String key, T listener, boolean persistListener) {
+ addListener(key, listener, persistListener ? _persistentListener : _onetimeListener);
+ }
+
+ /**
+ * Remove listener from the container.
+ * This operation removes both one-time and persistent listener from the specified key.
+ * @param key the key to remove
+ * @param listener the listener to remove
+ */
+ public void removeListener(String key, T listener) {
+ _lock.lock();
+ try {
+ removeFromListenerMap(key, listener, _persistentListener);
Review Comment:
I think my knowledge must be out-of-date. But still 2 questions,
1. Why not design the listener struture to enforce some basic metadata like type. So the type can be part of the listener object? In this case, you don't need to blindly try to remove it from all possible lists (imaging we have 3, 4, to n types in the future...).
2. Why you need to lock all the places? It seems to be simpler just adding sync the methods if it is really necessary.
##########
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/ListenerContainer.java:
##########
@@ -0,0 +1,186 @@
+package org.apache.helix.zookeeper.zkclient;
+
+/*
+ * 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.
+ */
+
+import com.google.common.annotations.VisibleForTesting;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+
+
+/**
+ * A thread-safe container wrapper class for Listeners registered to ZkClient.
+ * It stores 2 types of listener separately, one-time listener and persistent listener. The former ones are removed
+ * right after its consumption, while the latter need to be explicitly removed.
+ * @param <T> the type of listener
+ */
+public class ListenerContainer<T> {
+ private final ReentrantLock _lock = new ReentrantLock(true);
+ private final Map<String, Set<T>> _persistentListener = new ConcurrentHashMap<>();
+ private final Map<String, Set<T>> _onetimeListener = new ConcurrentHashMap<>();
+
+ /**
+ * Add listener to the container with specified key.
+ * @param key the key to register to
+ * @param listener the listener to register
+ * @param persistListener true if the listener is persistent
+ */
+ public void addListener(String key, T listener, boolean persistListener) {
+ addListener(key, listener, persistListener ? _persistentListener : _onetimeListener);
+ }
+
+ /**
+ * Remove listener from the container.
+ * This operation removes both one-time and persistent listener from the specified key.
+ * @param key the key to remove
+ * @param listener the listener to remove
+ */
+ public void removeListener(String key, T listener) {
+ _lock.lock();
+ try {
+ removeFromListenerMap(key, listener, _persistentListener);
+ removeFromListenerMap(key, listener, _onetimeListener);
+ } finally {
+ _lock.unlock();
+ }
+ }
+
+ /**
+ * Remove listener from the container.
+ * @param key the key to remove
+ * @param listener the listener to remove
+ * @param persistListener true if remove the persistent listener, otherwise remove the one-time listener
+ */
+ public void removeListener(String key, T listener, boolean persistListener) {
Review Comment:
Add to my previous point, I think it is really ugly to let user pass the type after they pass the type when adding and removing the listener. Once it is added, the container class should have enough information to tell if it is persist or not.
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