edu.umass.cs.reconfiguration.reconfigurationutils.ConsistentNodeConfig.java Source code

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Here is the source code for edu.umass.cs.reconfiguration.reconfigurationutils.ConsistentNodeConfig.java

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/*
 * Copyright (c) 2015 University of Massachusetts
 * 
 * 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.
 * 
 * Initial developer(s): V. Arun
 */
package edu.umass.cs.reconfiguration.reconfigurationutils;

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Set;

import org.json.JSONArray;
import org.json.JSONException;

import edu.umass.cs.nio.interfaces.NodeConfig;

/**
 *  This class isn't really used for anything other than as 
 * a parent for ConsistentReconfigurableNodeConfig, so it
 * has been declared abstract (even though it has no 
 * abstract methods).
 * @param <NodeIDType> 
 */
public abstract class ConsistentNodeConfig<NodeIDType> implements NodeConfig<NodeIDType> {

    private final NodeConfig<NodeIDType> nodeConfig;
    private Set<NodeIDType> nodes; // most recent cached copy

    private final ConsistentHashing<NodeIDType> CH; // need to refresh when nodeConfig changes

    /**
     * @param nc
     */
    public ConsistentNodeConfig(NodeConfig<NodeIDType> nc) {
        this.nodeConfig = nc;
        this.nodes = this.nodeConfig.getNodeIDs();
        this.CH = new ConsistentHashing<NodeIDType>(this.nodes);
    }

    private synchronized boolean refresh() {
        Set<NodeIDType> curActives = this.nodeConfig.getNodeIDs();
        if (curActives.equals(this.nodes))
            return false;
        this.nodes = (curActives);
        this.CH.refresh(curActives);
        return true;
    }

    /**
     * @param name
     * @return Consecutive servers on the consistent hash ring to which
     * this name hashes returned as an array.
     */
    public Set<NodeIDType> getReplicatedServers(String name) {
        refresh();
        return this.CH.getReplicatedServers(name);
    }

    @Override
    public boolean nodeExists(NodeIDType id) {
        return this.nodeConfig.nodeExists(id);
    }

    @Override
    public InetAddress getNodeAddress(NodeIDType id) {
        return this.nodeConfig.getNodeAddress(id);
    }

    @Override
    public InetAddress getBindAddress(NodeIDType id) {
        return this.nodeConfig.getBindAddress(id);
    }

    @Override
    public int getNodePort(NodeIDType id) {
        return this.nodeConfig.getNodePort(id);
    }

    /**
     * @param id
     * @return Socket address corresponding to node {@code id}.
     */
    public InetSocketAddress getNodeSocketAddress(NodeIDType id) {
        InetAddress ip = this.getNodeAddress(id);
        return (ip != null ? new InetSocketAddress(ip, this.getNodePort(id)) : null);
    }

    // FIXME: disallow the use of this method
    @Override
    public Set<NodeIDType> getNodeIDs() {
        throw new RuntimeException("The use of this method is not permitted");
        //return this.nodeConfig.getNodeIDs();
    }

    @Override
    public NodeIDType valueOf(String strValue) {
        return this.nodeConfig.valueOf(strValue);
    }

    @Override
    public Set<NodeIDType> getValuesFromStringSet(Set<String> strNodes) {
        return this.nodeConfig.getValuesFromStringSet(strNodes);
    }

    @Override
    public Set<NodeIDType> getValuesFromJSONArray(JSONArray array) throws JSONException {
        return this.nodeConfig.getValuesFromJSONArray(array);
    }
}