curator-master/curator-client/src/main/java/org/apache/curator/HandleHolder.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
 *
 *   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.curator;

import org.apache.curator.ensemble.EnsembleProvider;
import org.apache.curator.utils.ZookeeperFactory;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

class HandleHolder {
    private final ZookeeperFactory zookeeperFactory;
    private final Watcher watcher;
    private final EnsembleProvider ensembleProvider;
    private final int sessionTimeout;
    private final boolean canBeReadOnly;

    private volatile Helper helper;

    HandleHolder(
            ZookeeperFactory zookeeperFactory,
            Watcher watcher,
            EnsembleProvider ensembleProvider,
            int sessionTimeout,
            boolean canBeReadOnly) {
        this.zookeeperFactory = zookeeperFactory;
        this.watcher = watcher;
        this.ensembleProvider = ensembleProvider;
        this.sessionTimeout = sessionTimeout;
        this.canBeReadOnly = canBeReadOnly;
    }

    ZooKeeper getZooKeeper() throws Exception {
        return (helper != null) ? helper.getZooKeeper() : null;
    }

    int getNegotiatedSessionTimeoutMs() {
        return (helper != null) ? helper.getNegotiatedSessionTimeoutMs() : 0;
    }

    String getConnectionString() {
        return (helper != null) ? helper.getConnectionString() : null;
    }

    String getNewConnectionString() {
        String helperConnectionString = (helper != null) ? helper.getConnectionString() : null;
        String ensembleProviderConnectionString = ensembleProvider.getConnectionString();
        return ((helperConnectionString != null) && !ensembleProviderConnectionString.equals(helperConnectionString))
                ? ensembleProviderConnectionString
                : null;
    }

    void resetConnectionString(String connectionString) {
        if (helper != null) {
            helper.resetConnectionString(connectionString);
        }
    }

    void closeAndClear(int waitForShutdownTimeoutMs) throws Exception {
        internalClose(waitForShutdownTimeoutMs);
        helper = null;
    }

    void closeAndReset() throws Exception {
        internalClose(0);

        Helper.Data data = new Helper.Data(); // data shared between initial Helper and the un-synchronized Helper
        // first helper is synchronized when getZooKeeper is called. Subsequent calls
        // are not synchronized.
        //noinspection NonAtomicOperationOnVolatileField
        helper = new Helper(data) {
            @Override
            ZooKeeper getZooKeeper() throws Exception {
                synchronized (this) {
                    if (data.zooKeeperHandle == null) {
                        resetConnectionString(ensembleProvider.getConnectionString());
                        data.zooKeeperHandle = zookeeperFactory.newZooKeeper(
                                data.connectionString, sessionTimeout, watcher, canBeReadOnly);
                    }

                    helper = new Helper(data);

                    return super.getZooKeeper();
                }
            }
        };
    }

    private void internalClose(int waitForShutdownTimeoutMs) throws Exception {
        try {
            ZooKeeper zooKeeper = (helper != null) ? helper.getZooKeeper() : null;
            if (zooKeeper != null) {
                Watcher dummyWatcher = new Watcher() {
                    @Override
                    public void process(WatchedEvent event) {}
                };
                zooKeeper.register(
                        dummyWatcher); // clear the default watcher so that no new events get processed by mistake
                if (waitForShutdownTimeoutMs == 0) {
                    zooKeeper.close(); // coming from closeAndReset() which is executed in ZK's event thread. Cannot use
                    // zooKeeper.close(n) otherwise we'd get a dead lock
                } else {
                    zooKeeper.close(waitForShutdownTimeoutMs);
                }
            }
        } catch (InterruptedException dummy) {
            Thread.currentThread().interrupt();
        }
    }
}
