com.smartitengineering.cms.spi.lock.impl.distributed.ZooKeeperLockHandler.java Source code

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Here is the source code for com.smartitengineering.cms.spi.lock.impl.distributed.ZooKeeperLockHandler.java

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/*
 *
 * This is a simple Content Management System (CMS)
 * Copyright (C) 2011 Imran M Yousuf (imyousuf@smartitengineering.com)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.smartitengineering.cms.spi.lock.impl.distributed;

import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.google.inject.name.Named;
import com.smartitengineering.cms.api.factory.write.Lock;
import com.smartitengineering.cms.spi.lock.Key;
import com.smartitengineering.cms.spi.lock.LockHandler;
import java.io.IOException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 * @author imyousuf
 */
@Singleton
public class ZooKeeperLockHandler implements LockHandler, Watcher {

    private final transient Logger logger = LoggerFactory.getLogger(getClass());
    protected final ZKConfig config;

    @Inject
    public ZooKeeperLockHandler(@Named("zkConnectString") final String connectString,
            @Named("zkRootNode") final String rootNode, @Named("zkNodeId") final String nodeId,
            @Named("zkTimeout") final int timeout, final LocalLockRegistrar registrar) {
        final ZooKeeper zooKeeper;
        try {
            zooKeeper = new ZooKeeper(connectString, timeout, this);
        } catch (IOException ex) {
            logger.error("Could not intialize ZooKeeper connection!");
            throw new IllegalStateException(ex);
        }
        final String srootNode;
        if (rootNode.startsWith("/")) {
            srootNode = rootNode;
        } else {
            srootNode = new StringBuilder("/").append(rootNode).toString();
        }
        config = new ZKConfig(zooKeeper, srootNode, nodeId, registrar);
        logger.info("Connected to ZooKeeper server");
        try {
            initializeRootNode();
        } catch (Exception ex) {
            logger.error("Could not create root node!");
            throw new IllegalStateException(ex);
        }
        logger.info("Created root node");
    }

    public ZKConfig getConfig() {
        return config;
    }

    public Lock register(Key key) {
        ZKLock lock = getLock(key);
        return lock;
    }

    public void unregister(Key key) {
        ZKLock lock = getLock(key);
        if (lock.isLockOwned()) {
            lock.unlock();
        }
    }

    protected void createNodeIfNotExists(String node, boolean retry, byte... data)
            throws KeeperException, InterruptedException {
        final ZooKeeper zooKeeper = config.getZooKeeper();
        final Stat stat = zooKeeper.exists(node, false);
        if (stat == null) {
            zooKeeper.create(node, data == null ? new byte[] {} : data, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        } else if (data != null && data.length > 0) {
            zooKeeper.setData(node, data, stat.getVersion());
        }
    }

    protected ZKLock getLock(Key key) {
        ZKLock lock = new ZKLock(config, key);
        return lock;
    }

    public void process(WatchedEvent event) {
        //TODO Process WatchedEvent
    }

    private void initializeRootNode() throws KeeperException, InterruptedException {
        String node = config.getRootNode();
        createNodeIfNotExists(node, false);
    }
}