zookeeper-server/src/main/java/org/apache/zookeeper/server/watch/WatcherModeManager.java

/**
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.zookeeper.server.watch;

import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.zookeeper.Watcher;

class WatcherModeManager {
    private final Map<Key, WatcherMode> watcherModes = new ConcurrentHashMap<>();
    private final AtomicInteger recursiveQty = new AtomicInteger(0);

    private static class Key {
        private final Watcher watcher;
        private final String path;

        Key(Watcher watcher, String path) {
            this.watcher = watcher;
            this.path = path;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            Key key = (Key) o;
            return watcher.equals(key.watcher) && path.equals(key.path);
        }

        @Override
        public int hashCode() {
            return Objects.hash(watcher, path);
        }
    }

    // VisibleForTesting
    Map<Key, WatcherMode> getWatcherModes() {
        return watcherModes;
    }

    void setWatcherMode(Watcher watcher, String path, WatcherMode mode) {
        if (mode == WatcherMode.DEFAULT_WATCHER_MODE) {
            removeWatcher(watcher, path);
        } else {
            adjustRecursiveQty(watcherModes.put(new Key(watcher, path), mode), mode);
        }
    }

    WatcherMode getWatcherMode(Watcher watcher, String path) {
        return watcherModes.getOrDefault(new Key(watcher, path), WatcherMode.DEFAULT_WATCHER_MODE);
    }

    void removeWatcher(Watcher watcher, String path) {
        adjustRecursiveQty(watcherModes.remove(new Key(watcher, path)), WatcherMode.DEFAULT_WATCHER_MODE);
    }

    int getRecursiveQty() {
        return recursiveQty.get();
    }

    // recursiveQty is an optimization to avoid having to walk the map every time this value is needed
    private void adjustRecursiveQty(WatcherMode oldMode, WatcherMode newMode) {
        if (oldMode == null) {
            oldMode = WatcherMode.DEFAULT_WATCHER_MODE;
        }
        if (oldMode.isRecursive() != newMode.isRecursive()) {
            if (newMode.isRecursive()) {
                recursiveQty.incrementAndGet();
            } else {
                recursiveQty.decrementAndGet();
            }
        }
    }
}