package org.apache.cassandra.service.paxos;
/*
 * 
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 * 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
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import java.util.concurrent.atomic.AtomicInteger;

import org.apache.cassandra.db.ConsistencyLevel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.net.MessageIn;

ProposeCallback has two modes of operation, controlled by the failFast parameter.
In failFast mode, we will return a failure as soon as a majority of nodes reject
the proposal. This is used when replaying a proposal from an earlier leader.
Otherwise, we wait for either all replicas to reply or until we achieve
the desired quorum. We continue to wait for all replicas even after we know we cannot succeed
because we need to know if no node at all have accepted or if at least one has.
In the former case, a proposer is guaranteed no-one will
replay its value; in the latter we don't, so we must timeout in case another
leader replays it before we can; see CASSANDRA-6013
/**
 * ProposeCallback has two modes of operation, controlled by the failFast parameter.
 *
 * In failFast mode, we will return a failure as soon as a majority of nodes reject
 * the proposal. This is used when replaying a proposal from an earlier leader.
 *
 * Otherwise, we wait for either all replicas to reply or until we achieve
 * the desired quorum. We continue to wait for all replicas even after we know we cannot succeed
 * because we need to know if no node at all have accepted or if at least one has.
 * In the former case, a proposer is guaranteed no-one will
 * replay its value; in the latter we don't, so we must timeout in case another
 * leader replays it before we can; see CASSANDRA-6013
 */
public class ProposeCallback extends AbstractPaxosCallback<Boolean>
{
    private static final Logger logger = LoggerFactory.getLogger(ProposeCallback.class);

    private final AtomicInteger accepts = new AtomicInteger(0);
    private final int requiredAccepts;
    private final boolean failFast;

    public ProposeCallback(int totalTargets, int requiredTargets, boolean failFast, ConsistencyLevel consistency, long queryStartNanoTime)
    {
        super(totalTargets, consistency, queryStartNanoTime);
        this.requiredAccepts = requiredTargets;
        this.failFast = failFast;
    }

    public void response(MessageIn<Boolean> msg)
    {
        logger.trace("Propose response {} from {}", msg.payload, msg.from);

        if (msg.payload)
            accepts.incrementAndGet();

        latch.countDown();

        if (isSuccessful() || (failFast && (latch.getCount() + accepts.get() < requiredAccepts)))
        {
            while (latch.getCount() > 0)
                latch.countDown();
        }
    }

    public int getAcceptCount()
    {
        return accepts.get();
    }

    public boolean isSuccessful()
    {
        return accepts.get() >= requiredAccepts;
    }

    // Note: this is only reliable if !failFast
    public boolean isFullyRefused()
    {
        // We need to check the latch first to avoid racing with a late arrival
        // between the latch check and the accepts one
        return latch.getCount() == 0 && accepts.get() == 0;
    }
}