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HADOOP-10279. Create multiplexer, a requirement for the fair queue. (Contributed by Chris Li) 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1604090 13f79535-47bb-0310-9956-ffa450edef68
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Arpit Agarwal 2014-06-20 05:53:41 +00:00
parent af6c91a80c
commit e74d99b81e
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3
hadoop-common-project/hadoop-common/CHANGES.txt
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@ -442,6 +442,9 @@ Release 2.5.0 - UNRELEASED
HADOOP-10557. FsShell -cp -pa option for preserving extended ACLs.
(Akira Ajisaka via cnauroth)
HADOOP-10279. Create multiplexer, a requirement for the fair queue.
(Chris Li via Arpit Agarwal)
OPTIMIZATIONS
BUG FIXES

148
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/WeightedRoundRobinMultiplexer.java Normal file
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@ -0,0 +1,148 @@
/**
* 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.hadoop.ipc;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
/**
* Determines which queue to start reading from, occasionally drawing from
* low-priority queues in order to prevent starvation. Given the pull pattern
* [9, 4, 1] for 3 queues:
*
* The cycle is (a minimum of) 9+4+1=14 reads.
* Queue 0 is read (at least) 9 times
* Queue 1 is read (at least) 4 times
* Queue 2 is read (at least) 1 time
* Repeat
*
* There may be more reads than the minimum due to race conditions. This is
* allowed by design for performance reasons.
*/
public class WeightedRoundRobinMultiplexer {
// Config keys
public static final String IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY =
"faircallqueue.multiplexer.weights";
public static final Log LOG =
LogFactory.getLog(WeightedRoundRobinMultiplexer.class);
private final int numQueues; // The number of queues under our provisioning
private final AtomicInteger currentQueueIndex; // Current queue we're serving
private final AtomicInteger requestsLeft; // Number of requests left for this queue
private int[] queueWeights; // The weights for each queue
public WeightedRoundRobinMultiplexer(int aNumQueues, String ns,
Configuration conf) {
if (aNumQueues <= 0) {
throw new IllegalArgumentException("Requested queues (" + aNumQueues +
") must be greater than zero.");
}
this.numQueues = aNumQueues;
this.queueWeights = conf.getInts(ns + "." +
IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY);
if (this.queueWeights.length == 0) {
this.queueWeights = getDefaultQueueWeights(this.numQueues);
} else if (this.queueWeights.length != this.numQueues) {
throw new IllegalArgumentException(ns + "." +
IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY + " must specify exactly " +
this.numQueues + " weights: one for each priority level.");
}
this.currentQueueIndex = new AtomicInteger(0);
this.requestsLeft = new AtomicInteger(this.queueWeights[0]);
LOG.info("WeightedRoundRobinMultiplexer is being used.");
}
/**
* Creates default weights for each queue. The weights are 2^N.
*/
private int[] getDefaultQueueWeights(int aNumQueues) {
int[] weights = new int[aNumQueues];
int weight = 1; // Start low
for(int i = aNumQueues - 1; i >= 0; i--) { // Start at lowest queue
weights[i] = weight;
weight *= 2; // Double every iteration
}
return weights;
}
/**
* Move to the next queue.
*/
private void moveToNextQueue() {
int thisIdx = this.currentQueueIndex.get();
// Wrap to fit in our bounds
int nextIdx = (thisIdx + 1) % this.numQueues;
// Set to next index: once this is called, requests will start being
// drawn from nextIdx, but requestsLeft will continue to decrement into
// the negatives
this.currentQueueIndex.set(nextIdx);
// Finally, reset requestsLeft. This will enable moveToNextQueue to be
// called again, for the new currentQueueIndex
this.requestsLeft.set(this.queueWeights[nextIdx]);
}
/**
* Advances the index, which will change the current index
* if called enough times.
*/
private void advanceIndex() {
// Since we did read, we should decrement
int requestsLeftVal = this.requestsLeft.decrementAndGet();
// Strict compare with zero (instead of inequality) so that if another
// thread decrements requestsLeft, only one thread will be responsible
// for advancing currentQueueIndex
if (requestsLeftVal == 0) {
// This is guaranteed to be called exactly once per currentQueueIndex
this.moveToNextQueue();
}
}
/**
* Gets the current index. Should be accompanied by a call to
* advanceIndex at some point.
*/
private int getCurrentIndex() {
return this.currentQueueIndex.get();
}
/**
* Use the mux by getting and advancing index.
*/
public int getAndAdvanceCurrentIndex() {
int idx = this.getCurrentIndex();
this.advanceIndex();
return idx;
}
}

142
hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestWeightedRoundRobinMultiplexer.java Normal file
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@ -0,0 +1,142 @@
/**
* 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.hadoop.ipc;
import static org.junit.Assert.assertEquals;
import org.junit.Test;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import static org.apache.hadoop.ipc.WeightedRoundRobinMultiplexer.IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY;
public class TestWeightedRoundRobinMultiplexer {
public static final Log LOG = LogFactory.getLog(TestWeightedRoundRobinMultiplexer.class);
private WeightedRoundRobinMultiplexer mux;
@Test(expected=IllegalArgumentException.class)
public void testInstantiateNegativeMux() {
mux = new WeightedRoundRobinMultiplexer(-1, "", new Configuration());
}
@Test(expected=IllegalArgumentException.class)
public void testInstantiateZeroMux() {
mux = new WeightedRoundRobinMultiplexer(0, "", new Configuration());
}
@Test(expected=IllegalArgumentException.class)
public void testInstantiateIllegalMux() {
Configuration conf = new Configuration();
conf.setStrings("namespace." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
"1", "2", "3");
// ask for 3 weights with 2 queues
mux = new WeightedRoundRobinMultiplexer(2, "namespace", conf);
}
@Test
public void testLegalInstantiation() {
Configuration conf = new Configuration();
conf.setStrings("namespace." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
"1", "2", "3");
// ask for 3 weights with 3 queues
mux = new WeightedRoundRobinMultiplexer(3, "namespace.", conf);
}
@Test
public void testDefaultPattern() {
// Mux of size 1: 0 0 0 0 0, etc
mux = new WeightedRoundRobinMultiplexer(1, "", new Configuration());
for(int i = 0; i < 10; i++) {
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
}
// Mux of size 2: 0 0 1 0 0 1 0 0 1, etc
mux = new WeightedRoundRobinMultiplexer(2, "", new Configuration());
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
// Size 3: 4x0 2x1 1x2, etc
mux = new WeightedRoundRobinMultiplexer(3, "", new Configuration());
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
// Size 4: 8x0 4x1 2x2 1x3
mux = new WeightedRoundRobinMultiplexer(4, "", new Configuration());
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
assertEquals(mux.getAndAdvanceCurrentIndex(), 3);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
}
@Test
public void testCustomPattern() {
// 1x0 1x1
Configuration conf = new Configuration();
conf.setStrings("test.custom." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
"1", "1");
mux = new WeightedRoundRobinMultiplexer(2, "test.custom", conf);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
// 1x0 3x1 2x2
conf.setStrings("test.custom." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
"1", "3", "2");
mux = new WeightedRoundRobinMultiplexer(3, "test.custom", conf);
for(int i = 0; i < 5; i++) {
assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
} // Ensure pattern repeats
}
}