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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * 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.cassandra.service;

import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;

import org.apache.cassandra.locator.ReplicaPlan;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.net.Message;
import org.apache.cassandra.db.WriteType;

/**
 * Handles blocking writes for ONE, ANY, TWO, THREE, QUORUM, and ALL consistency levels.
 */
public class WriteResponseHandler extends AbstractWriteResponseHandler
{
    protected static final Logger logger = LoggerFactory.getLogger(WriteResponseHandler.class);

    protected volatile int responses;
    private static final AtomicIntegerFieldUpdater responsesUpdater
            = AtomicIntegerFieldUpdater.newUpdater(WriteResponseHandler.class, "responses");

    public WriteResponseHandler(ReplicaPlan.ForTokenWrite replicaPlan,
                                Runnable callback,
                                WriteType writeType,
                                long queryStartNanoTime)
    {
        super(replicaPlan, callback, writeType, queryStartNanoTime);
        responses = blockFor();
    }

    public WriteResponseHandler(ReplicaPlan.ForTokenWrite replicaPlan, WriteType writeType, long queryStartNanoTime)
    {
        this(replicaPlan, null, writeType, queryStartNanoTime);
    }

    public void onResponse(Message m)
    {
        if (responsesUpdater.decrementAndGet(this) == 0)
            signal();
        //Must be last after all subclass processing
        //The two current subclasses both assume logResponseToIdealCLDelegate is called
        //here.
        logResponseToIdealCLDelegate(m);
    }

    protected int ackCount()
    {
        return blockFor() - responses;
    }
}