org.gridgain.client.balancer.GridClientRoundRobinBalancer Maven / Gradle / Ivy

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Java-based middleware for in-memory processing of big data in a distributed environment.
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/* 
 Copyright (C) GridGain Systems. All Rights Reserved.
 
 Licensed 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.gridgain.client.balancer;

import org.gridgain.client.*;

import java.util.*;
import java.util.concurrent.locks.*;

/**
 * Simple balancer that implements round-robin balancing.
 */
public class GridClientRoundRobinBalancer extends GridClientBalancerAdapter implements GridClientTopologyListener {
    /** Lock. */
    private Lock lock = new ReentrantLock();

    /** Nodes to share load. */
    private LinkedList nodeQueue = new LinkedList<>();
    
    /** {@inheritDoc} */
    @Override public GridClientNode balancedNode(Collection nodes)
        throws GridClientException {
        assert !nodes.isEmpty();

        if (isPreferDirectNodes()) {
            Collection direct = selectDirectNodes(nodes);

            int directSize = direct.size();

            // If set of direct nodes is not empty and differ from original one
            // replace original set of nodes with directly available.
            if (directSize > 0 && directSize < nodes.size())
                nodes = direct;
        }

        Map lookup = new HashMap<>(nodes.size());

        for (GridClientNode node : nodes)
            lookup.put(node.nodeId(), node);

        lock.lock();

        try {
            GridClientNode balanced = null;

            for (Iterator iter = nodeQueue.iterator(); iter.hasNext();) {
                UUID nodeId = iter.next();

                balanced = lookup.get(nodeId);

                if (balanced != null) {
                    iter.remove();

                    break;
                }
            }

            if (balanced != null) {
                nodeQueue.addLast(balanced.nodeId());

                return balanced;
            }

            throw new GridClientException("Passed nodes doesn't present in topology " +
                "[nodes=" + nodes + ", top=" + nodeQueue);
        }
        finally {
            lock.unlock();
        }
    }

    /** {@inheritDoc} */
    @Override public void onNodeAdded(GridClientNode node) {
        lock.lock();

        try {
            nodeQueue.addFirst(node.nodeId());
        }
        finally {
            lock.unlock();
        }
    }

    /** {@inheritDoc} */
    @Override public void onNodeRemoved(GridClientNode node) {
        lock.lock();
        
        try {
            nodeQueue.remove(node.nodeId());
        }
        finally {
            lock.unlock();
        }
    }
}