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VoltDB client interface libraries
There is a newer version: 13.3.2-preview1
/* This file is part of VoltDB.
 * Copyright (C) 2008-2017 VoltDB Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with VoltDB.  If not, see .
 */

package org.voltdb.client;

import org.voltcore.logging.VoltLogger;
import org.voltcore.network.ReverseDNSCache;
import org.voltcore.utils.EstTimeUpdater;

/**
 * Factory for constructing instances of the {@link Client} interface
 *
 */
public abstract class ClientFactory {
    // If m_preserveResources is set m_activeClientCount will always be 1 irrespective of the number of clients
    // initialized through the factory.
    static int m_activeClientCount = 0;
    static boolean m_preserveResources = false;

    /**
     * Create a {@link Client} with no connections. The Client will be optimized to send stored procedure invocations
     * that are 128 bytes in size. Authentication will use a blank username and password unless
     * you use the @deprecated createConnection methods.
     *
     * @return Newly constructed {@link Client}
     */
    public static Client createClient() {
        return createClient(new ClientConfig());
    }

    /**
     * Recommended method for creating a client. Using a ClientConfig object ensures
     * that a client application is isolated from changes to the configuration options.
     * Authentication credentials are provided at construction time with this method
     * instead of when invoking createConnection.
     *
     * @param config A ClientConfig object specifying what type of client to create
     * @return A configured client
     */
    public static Client createClient(ClientConfig config) {
        Client client = null;
        synchronized (ClientFactory.class) {
            if (!m_preserveResources && ++m_activeClientCount == 1) {
                VoltLogger.startAsynchronousLogging();
                EstTimeUpdater.start();
                ReverseDNSCache.start();
            }
        }
        client = new ClientImpl(config);
        return client;
    }

    public static synchronized void decreaseClientNum() throws InterruptedException {
        // the client is the last alive client. Before exit, close all the static resources and threads.
        if (!m_preserveResources && m_activeClientCount <= 1) {
            m_activeClientCount = 0;
            //Shut down the logger.
            VoltLogger.shutdownAsynchronousLogging();
            //Estimate Time Updater stop updates.
            EstTimeUpdater.stop();
            //stop ReverseDNSCache.
            ReverseDNSCache.stop();
        }
        else {
            m_activeClientCount--;
        }
    }

    public static synchronized void increaseClientCountToOne() {
        // This method is intended to ensure that the resources needed to create clients
        // are always initialized and won't be released with the active client count goes to zero.
        m_preserveResources = true;
        VoltLogger.startAsynchronousLogging();
        EstTimeUpdater.start();
        ReverseDNSCache.start();
        m_activeClientCount = 1;
    }
}