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
This commit is contained in:
Arpit Agarwal
parent
af6c91a80c
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e74d99b81e
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@ -442,6 +442,9 @@ Release 2.5.0 - UNRELEASED
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HADOOP-10557. FsShell -cp -pa option for preserving extended ACLs.
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HADOOP-10557. FsShell -cp -pa option for preserving extended ACLs.
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(Akira Ajisaka via cnauroth)
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(Akira Ajisaka via cnauroth)
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HADOOP-10279. Create multiplexer, a requirement for the fair queue.
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(Chris Li via Arpit Agarwal)
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OPTIMIZATIONS
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OPTIMIZATIONS
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BUG FIXES
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BUG FIXES
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@ -0,0 +1,148 @@
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/**
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.hadoop.ipc;
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import java.util.concurrent.atomic.AtomicInteger;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.apache.hadoop.conf.Configuration;
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/**
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* Determines which queue to start reading from, occasionally drawing from
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* low-priority queues in order to prevent starvation. Given the pull pattern
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* [9, 4, 1] for 3 queues:
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*
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* The cycle is (a minimum of) 9+4+1=14 reads.
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* Queue 0 is read (at least) 9 times
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* Queue 1 is read (at least) 4 times
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* Queue 2 is read (at least) 1 time
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* Repeat
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*
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* There may be more reads than the minimum due to race conditions. This is
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* allowed by design for performance reasons.
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*/
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public class WeightedRoundRobinMultiplexer {
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// Config keys
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public static final String IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY =
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"faircallqueue.multiplexer.weights";
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public static final Log LOG =
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LogFactory.getLog(WeightedRoundRobinMultiplexer.class);
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private final int numQueues; // The number of queues under our provisioning
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private final AtomicInteger currentQueueIndex; // Current queue we're serving
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private final AtomicInteger requestsLeft; // Number of requests left for this queue
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private int[] queueWeights; // The weights for each queue
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public WeightedRoundRobinMultiplexer(int aNumQueues, String ns,
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Configuration conf) {
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if (aNumQueues <= 0) {
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throw new IllegalArgumentException("Requested queues (" + aNumQueues +
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") must be greater than zero.");
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}
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this.numQueues = aNumQueues;
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this.queueWeights = conf.getInts(ns + "." +
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IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY);
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if (this.queueWeights.length == 0) {
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this.queueWeights = getDefaultQueueWeights(this.numQueues);
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} else if (this.queueWeights.length != this.numQueues) {
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throw new IllegalArgumentException(ns + "." +
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IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY + " must specify exactly " +
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this.numQueues + " weights: one for each priority level.");
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}
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this.currentQueueIndex = new AtomicInteger(0);
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this.requestsLeft = new AtomicInteger(this.queueWeights[0]);
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LOG.info("WeightedRoundRobinMultiplexer is being used.");
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}
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/**
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* Creates default weights for each queue. The weights are 2^N.
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*/
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private int[] getDefaultQueueWeights(int aNumQueues) {
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int[] weights = new int[aNumQueues];
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int weight = 1; // Start low
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for(int i = aNumQueues - 1; i >= 0; i--) { // Start at lowest queue
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weights[i] = weight;
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weight *= 2; // Double every iteration
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}
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return weights;
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}
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/**
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* Move to the next queue.
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*/
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private void moveToNextQueue() {
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int thisIdx = this.currentQueueIndex.get();
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// Wrap to fit in our bounds
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int nextIdx = (thisIdx + 1) % this.numQueues;
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// Set to next index: once this is called, requests will start being
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// drawn from nextIdx, but requestsLeft will continue to decrement into
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// the negatives
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this.currentQueueIndex.set(nextIdx);
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// Finally, reset requestsLeft. This will enable moveToNextQueue to be
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// called again, for the new currentQueueIndex
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this.requestsLeft.set(this.queueWeights[nextIdx]);
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}
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/**
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* Advances the index, which will change the current index
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* if called enough times.
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*/
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private void advanceIndex() {
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// Since we did read, we should decrement
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int requestsLeftVal = this.requestsLeft.decrementAndGet();
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// Strict compare with zero (instead of inequality) so that if another
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// thread decrements requestsLeft, only one thread will be responsible
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// for advancing currentQueueIndex
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if (requestsLeftVal == 0) {
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// This is guaranteed to be called exactly once per currentQueueIndex
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this.moveToNextQueue();
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}
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}
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/**
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* Gets the current index. Should be accompanied by a call to
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* advanceIndex at some point.
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*/
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private int getCurrentIndex() {
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return this.currentQueueIndex.get();
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}
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/**
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* Use the mux by getting and advancing index.
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*/
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public int getAndAdvanceCurrentIndex() {
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int idx = this.getCurrentIndex();
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this.advanceIndex();
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return idx;
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}
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}
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@ -0,0 +1,142 @@
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/**
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.hadoop.ipc;
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import static org.junit.Assert.assertEquals;
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import org.junit.Test;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.apache.hadoop.conf.Configuration;
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import static org.apache.hadoop.ipc.WeightedRoundRobinMultiplexer.IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY;
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public class TestWeightedRoundRobinMultiplexer {
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public static final Log LOG = LogFactory.getLog(TestWeightedRoundRobinMultiplexer.class);
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private WeightedRoundRobinMultiplexer mux;
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@Test(expected=IllegalArgumentException.class)
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public void testInstantiateNegativeMux() {
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mux = new WeightedRoundRobinMultiplexer(-1, "", new Configuration());
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}
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@Test(expected=IllegalArgumentException.class)
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public void testInstantiateZeroMux() {
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mux = new WeightedRoundRobinMultiplexer(0, "", new Configuration());
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}
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@Test(expected=IllegalArgumentException.class)
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public void testInstantiateIllegalMux() {
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Configuration conf = new Configuration();
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conf.setStrings("namespace." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
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"1", "2", "3");
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// ask for 3 weights with 2 queues
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mux = new WeightedRoundRobinMultiplexer(2, "namespace", conf);
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}
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@Test
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public void testLegalInstantiation() {
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Configuration conf = new Configuration();
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conf.setStrings("namespace." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
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"1", "2", "3");
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// ask for 3 weights with 3 queues
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mux = new WeightedRoundRobinMultiplexer(3, "namespace.", conf);
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}
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@Test
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public void testDefaultPattern() {
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// Mux of size 1: 0 0 0 0 0, etc
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mux = new WeightedRoundRobinMultiplexer(1, "", new Configuration());
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for(int i = 0; i < 10; i++) {
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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}
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// Mux of size 2: 0 0 1 0 0 1 0 0 1, etc
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mux = new WeightedRoundRobinMultiplexer(2, "", new Configuration());
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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// Size 3: 4x0 2x1 1x2, etc
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mux = new WeightedRoundRobinMultiplexer(3, "", new Configuration());
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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// Size 4: 8x0 4x1 2x2 1x3
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mux = new WeightedRoundRobinMultiplexer(4, "", new Configuration());
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 3);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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}
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@Test
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public void testCustomPattern() {
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// 1x0 1x1
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Configuration conf = new Configuration();
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conf.setStrings("test.custom." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
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"1", "1");
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mux = new WeightedRoundRobinMultiplexer(2, "test.custom", conf);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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// 1x0 3x1 2x2
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conf.setStrings("test.custom." + IPC_CALLQUEUE_WRRMUX_WEIGHTS_KEY,
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"1", "3", "2");
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mux = new WeightedRoundRobinMultiplexer(3, "test.custom", conf);
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for(int i = 0; i < 5; i++) {
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assertEquals(mux.getAndAdvanceCurrentIndex(), 0);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 1);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
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assertEquals(mux.getAndAdvanceCurrentIndex(), 2);
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} // Ensure pattern repeats
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}
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}
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