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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.
/*
* 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.net;
import java.net.InetAddress;
import java.util.concurrent.TimeUnit;
import com.google.common.util.concurrent.RateLimiter;
import org.apache.cassandra.utils.SlidingTimeRate;
import org.apache.cassandra.utils.TimeSource;
import org.apache.cassandra.utils.concurrent.IntervalLock;
/**
* The rate-based back-pressure state, tracked per replica host.
*
*
* This back-pressure state is made up of the following attributes:
*
* - windowSize: the length of the back-pressure window in milliseconds.
* - incomingRate: the rate of back-pressure supporting incoming messages.
* - outgoingRate: the rate of back-pressure supporting outgoing messages.
* - rateLimiter: the rate limiter to eventually apply to outgoing messages.
*
*
* The incomingRate and outgoingRate are updated together when a response is received to guarantee consistency between
* the two.
*
* It also provides methods to exclusively lock/release back-pressure windows at given intervals;
* this allows to apply back-pressure even under concurrent modifications. Please also note a read lock is acquired
* during response processing so that no concurrent rate updates can screw rate computations.
*/
class RateBasedBackPressureState extends IntervalLock implements BackPressureState
{
private final InetAddress host;
private final long windowSize;
final SlidingTimeRate incomingRate;
final SlidingTimeRate outgoingRate;
final RateLimiter rateLimiter;
RateBasedBackPressureState(InetAddress host, TimeSource timeSource, long windowSize)
{
super(timeSource);
this.host = host;
this.windowSize = windowSize;
this.incomingRate = new SlidingTimeRate(timeSource, this.windowSize, this.windowSize / 10, TimeUnit.MILLISECONDS);
this.outgoingRate = new SlidingTimeRate(timeSource, this.windowSize, this.windowSize / 10, TimeUnit.MILLISECONDS);
this.rateLimiter = RateLimiter.create(Double.POSITIVE_INFINITY);
}
@Override
public void onMessageSent(MessageOut message) {}
@Override
public void onResponseReceived()
{
readLock().lock();
try
{
incomingRate.update(1);
outgoingRate.update(1);
}
finally
{
readLock().unlock();
}
}
@Override
public void onResponseTimeout()
{
readLock().lock();
try
{
outgoingRate.update(1);
}
finally
{
readLock().unlock();
}
}
@Override
public double getBackPressureRateLimit()
{
return rateLimiter.getRate();
}
@Override
public InetAddress getHost()
{
return host;
}
@Override
public boolean equals(Object obj)
{
if (obj instanceof RateBasedBackPressureState)
{
RateBasedBackPressureState other = (RateBasedBackPressureState) obj;
return this.host.equals(other.host);
}
return false;
}
@Override
public int hashCode()
{
return this.host.hashCode();
}
@Override
public String toString()
{
return String.format("[host: %s, incoming rate: %.3f, outgoing rate: %.3f, rate limit: %.3f]",
host, incomingRate.get(TimeUnit.SECONDS), outgoingRate.get(TimeUnit.SECONDS), rateLimiter.getRate());
}
}