subprojects/s4-comm/src/main/java/org/apache/s4/comm/tcp/DefaultRemoteEmitters.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.s4.comm.tcp;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.apache.s4.base.RemoteEmitter;
import org.apache.s4.comm.RemoteEmitterFactory;
import org.apache.s4.comm.topology.Cluster;

import com.google.inject.Inject;
import com.google.inject.Singleton;

@Singleton
public class DefaultRemoteEmitters implements RemoteEmitters {

    ConcurrentMap<Cluster, RemoteEmitter> emitters = new ConcurrentHashMap<Cluster, RemoteEmitter>();

    @Inject
    RemoteEmitterFactory emitterFactory;

    /*
     * (non-Javadoc)
     * 
     * @see org.apache.s4.comm.tcp.RemoteEmitters#getEmitter(org.apache.s4.comm.topology.Cluster)
     */
    @Override
    public RemoteEmitter getEmitter(Cluster topology) {
        RemoteEmitter emitter = emitters.get(topology);
        if (emitter == null) {
            RemoteEmitter newEmitter = emitterFactory.createRemoteEmitter(topology);
            emitter = emitters.putIfAbsent(topology, newEmitter);
            if (emitter == null) {
                emitter = newEmitter;
            } else {
                // use the existing emitter instead
                newEmitter.close();
            }
        }
        return emitter;
    }
}