HDFS-7891. A block placement policy with best rack failure tolerance. Contributed by Walter Su
This commit is contained in:
Tsz-Wo Nicholas Sze
parent
4308910eed
commit
9595cc003c
@ -323,6 +323,9 @@ Release 2.8.0 - UNRELEASED
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NEW FEATURES
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HDFS-7891. A block placement policy with best rack failure tolerance.
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(Walter Su via szetszwo)
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IMPROVEMENTS
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HDFS-3918. EditLogTailer shouldn't log WARN when other node
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@ -237,7 +237,7 @@ private DatanodeStorageInfo[] chooseTarget(int numOfReplicas,
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* is independent of the number of chosen nodes, as it is calculated
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* using the target number of replicas.
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*/
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private int[] getMaxNodesPerRack(int numOfChosen, int numOfReplicas) {
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protected int[] getMaxNodesPerRack(int numOfChosen, int numOfReplicas) {
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int clusterSize = clusterMap.getNumOfLeaves();
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int totalNumOfReplicas = numOfChosen + numOfReplicas;
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if (totalNumOfReplicas > clusterSize) {
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@ -0,0 +1,154 @@
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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.hdfs.server.blockmanagement;
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import org.apache.hadoop.classification.InterfaceAudience;
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import org.apache.hadoop.fs.StorageType;
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import org.apache.hadoop.net.Node;
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import org.apache.hadoop.net.NodeBase;
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import java.util.*;
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/**
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* The class is responsible for choosing the desired number of targets
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* for placing block replicas.
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* The strategy is that it tries its best to place the replicas to most racks.
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*/
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@InterfaceAudience.Private
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public class BlockPlacementPolicyRackFaultTolarent extends BlockPlacementPolicyDefault {
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@Override
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protected int[] getMaxNodesPerRack(int numOfChosen, int numOfReplicas) {
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int clusterSize = clusterMap.getNumOfLeaves();
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int totalNumOfReplicas = numOfChosen + numOfReplicas;
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if (totalNumOfReplicas > clusterSize) {
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numOfReplicas -= (totalNumOfReplicas-clusterSize);
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totalNumOfReplicas = clusterSize;
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}
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// No calculation needed when there is only one rack or picking one node.
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int numOfRacks = clusterMap.getNumOfRacks();
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if (numOfRacks == 1 || totalNumOfReplicas <= 1) {
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return new int[] {numOfReplicas, totalNumOfReplicas};
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}
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if(totalNumOfReplicas<numOfRacks){
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return new int[] {numOfReplicas, 1};
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}
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int maxNodesPerRack = (totalNumOfReplicas - 1) / numOfRacks + 1;
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return new int[] {numOfReplicas, maxNodesPerRack};
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}
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/**
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* Choose numOfReplicas in order:
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* 1. If total replica expected is less than numOfRacks in cluster, it choose
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* randomly.
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* 2. If total replica expected is bigger than numOfRacks, it choose:
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* 2a. Fill each rack exactly (maxNodesPerRack-1) replicas.
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* 2b. For some random racks, place one more replica to each one of them, until
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* numOfReplicas have been chosen. <br>
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* In the end, the difference of the numbers of replicas for each two racks
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* is no more than 1.
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* Either way it always prefer local storage.
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* @return local node of writer
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*/
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@Override
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protected Node chooseTargetInOrder(int numOfReplicas,
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Node writer,
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final Set<Node> excludedNodes,
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final long blocksize,
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final int maxNodesPerRack,
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final List<DatanodeStorageInfo> results,
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final boolean avoidStaleNodes,
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final boolean newBlock,
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EnumMap<StorageType, Integer> storageTypes)
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throws NotEnoughReplicasException {
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int totalReplicaExpected = results.size() + numOfReplicas;
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int numOfRacks = clusterMap.getNumOfRacks();
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if (totalReplicaExpected < numOfRacks ||
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totalReplicaExpected % numOfRacks == 0) {
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writer = chooseOnce(numOfReplicas, writer, excludedNodes, blocksize,
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maxNodesPerRack, results, avoidStaleNodes, storageTypes);
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return writer;
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}
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assert totalReplicaExpected > (maxNodesPerRack -1) * numOfRacks;
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// Calculate numOfReplicas for filling each rack exactly (maxNodesPerRack-1)
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// replicas.
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HashMap<String, Integer> rackCounts = new HashMap<>();
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for (DatanodeStorageInfo dsInfo : results) {
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String rack = dsInfo.getDatanodeDescriptor().getNetworkLocation();
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Integer count = rackCounts.get(rack);
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if (count != null) {
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rackCounts.put(rack, count + 1);
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} else {
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rackCounts.put(rack, 1);
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}
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}
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int excess = 0; // Sum of the above (maxNodesPerRack-1) part of nodes in results
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for (int count : rackCounts.values()) {
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if (count > maxNodesPerRack -1) {
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excess += count - (maxNodesPerRack -1);
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}
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}
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numOfReplicas = Math.min(totalReplicaExpected - results.size(),
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(maxNodesPerRack -1) * numOfRacks - (results.size() - excess));
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// Fill each rack exactly (maxNodesPerRack-1) replicas.
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writer = chooseOnce(numOfReplicas, writer, new HashSet<>(excludedNodes),
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blocksize, maxNodesPerRack -1, results, avoidStaleNodes, storageTypes);
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for (DatanodeStorageInfo resultStorage : results) {
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addToExcludedNodes(resultStorage.getDatanodeDescriptor(), excludedNodes);
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}
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// For some racks, place one more replica to each one of them.
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numOfReplicas = totalReplicaExpected - results.size();
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chooseOnce(numOfReplicas, writer, excludedNodes, blocksize,
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maxNodesPerRack, results, avoidStaleNodes, storageTypes);
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return writer;
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}
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/**
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* Randomly choose <i>numOfReplicas</i> targets from the given <i>scope</i>.
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* Except that 1st replica prefer local storage.
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* @return local node of writer.
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*/
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private Node chooseOnce(int numOfReplicas,
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Node writer,
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final Set<Node> excludedNodes,
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final long blocksize,
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final int maxNodesPerRack,
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final List<DatanodeStorageInfo> results,
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final boolean avoidStaleNodes,
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EnumMap<StorageType, Integer> storageTypes)
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throws NotEnoughReplicasException {
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if (numOfReplicas == 0) {
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return writer;
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}
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writer = chooseLocalStorage(writer, excludedNodes, blocksize,
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maxNodesPerRack, results, avoidStaleNodes, storageTypes, true)
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.getDatanodeDescriptor();
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if (--numOfReplicas == 0) {
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return writer;
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}
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chooseRandom(numOfReplicas, NodeBase.ROOT, excludedNodes, blocksize,
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maxNodesPerRack, results, avoidStaleNodes, storageTypes);
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return writer;
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}
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}
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@ -0,0 +1,209 @@
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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.hdfs.server.namenode;
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.fs.CreateFlag;
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import org.apache.hadoop.fs.permission.FsPermission;
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import org.apache.hadoop.fs.permission.PermissionStatus;
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import org.apache.hadoop.hdfs.DFSConfigKeys;
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import org.apache.hadoop.hdfs.DFSUtil;
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import org.apache.hadoop.hdfs.HdfsConfiguration;
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import org.apache.hadoop.hdfs.MiniDFSCluster;
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import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
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import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
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import org.apache.hadoop.hdfs.protocol.LocatedBlock;
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import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy;
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import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyRackFaultTolarent;
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import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
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import org.apache.hadoop.net.StaticMapping;
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import org.junit.After;
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import org.junit.Before;
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import org.junit.Test;
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import java.io.IOException;
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import java.util.*;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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public class TestBlockPlacementPolicyRackFaultTolarent {
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private static final int DEFAULT_BLOCK_SIZE = 1024;
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private MiniDFSCluster cluster = null;
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private NamenodeProtocols nameNodeRpc = null;
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private FSNamesystem namesystem = null;
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private PermissionStatus perm = null;
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@Before
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public void setup() throws IOException {
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StaticMapping.resetMap();
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Configuration conf = new HdfsConfiguration();
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final ArrayList<String> rackList = new ArrayList<String>();
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final ArrayList<String> hostList = new ArrayList<String>();
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for (int i = 0; i < 10; i++) {
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for (int j = 0; j < 2; j++) {
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rackList.add("/rack" + i);
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hostList.add("/host" + i + j);
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}
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}
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conf.setClass(DFSConfigKeys.DFS_BLOCK_REPLICATOR_CLASSNAME_KEY,
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BlockPlacementPolicyRackFaultTolarent.class,
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BlockPlacementPolicy.class);
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conf.setLong(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, DEFAULT_BLOCK_SIZE);
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conf.setInt(DFSConfigKeys.DFS_BYTES_PER_CHECKSUM_KEY, DEFAULT_BLOCK_SIZE / 2);
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cluster = new MiniDFSCluster.Builder(conf)
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.numDataNodes(hostList.size())
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.racks(rackList.toArray(new String[rackList.size()]))
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.hosts(hostList.toArray(new String[hostList.size()]))
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.build();
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cluster.waitActive();
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nameNodeRpc = cluster.getNameNodeRpc();
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namesystem = cluster.getNamesystem();
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perm = new PermissionStatus("TestBlockPlacementPolicyEC", null,
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FsPermission.getDefault());
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}
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@After
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public void teardown() {
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if (cluster != null) {
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cluster.shutdown();
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}
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}
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@Test
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public void testChooseTarget() throws Exception {
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doTestChooseTargetNormalCase();
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doTestChooseTargetSpecialCase();
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}
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private void doTestChooseTargetNormalCase() throws Exception {
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String clientMachine = "client.foo.com";
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short[][] testSuite = {
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{3, 2}, {3, 7}, {3, 8}, {3, 10}, {9, 1}, {10, 1}, {10, 6}, {11, 6},
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{11, 9}
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};
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// Test 5 files
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int fileCount = 0;
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for (int i = 0; i < 5; i++) {
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for (short[] testCase : testSuite) {
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short replication = testCase[0];
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short additionalReplication = testCase[1];
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String src = "/testfile" + (fileCount++);
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// Create the file with client machine
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HdfsFileStatus fileStatus = namesystem.startFile(src, perm,
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clientMachine, clientMachine, EnumSet.of(CreateFlag.CREATE), true,
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replication, DEFAULT_BLOCK_SIZE, null, false);
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//test chooseTarget for new file
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LocatedBlock locatedBlock = nameNodeRpc.addBlock(src, clientMachine,
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null, null, fileStatus.getFileId(), null);
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doTestLocatedBlock(replication, locatedBlock);
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//test chooseTarget for existing file.
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LocatedBlock additionalLocatedBlock =
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nameNodeRpc.getAdditionalDatanode(src, fileStatus.getFileId(),
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locatedBlock.getBlock(), locatedBlock.getLocations(),
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locatedBlock.getStorageIDs(), new DatanodeInfo[0],
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additionalReplication, clientMachine);
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doTestLocatedBlock(replication + additionalReplication, additionalLocatedBlock);
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}
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}
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}
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/**
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* Test more randomly. So it covers some special cases.
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* Like when some racks already have 2 replicas, while some racks have none,
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* we should choose the racks that have none.
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*/
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private void doTestChooseTargetSpecialCase() throws Exception {
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String clientMachine = "client.foo.com";
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// Test 5 files
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String src = "/testfile_1_";
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// Create the file with client machine
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HdfsFileStatus fileStatus = namesystem.startFile(src, perm,
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clientMachine, clientMachine, EnumSet.of(CreateFlag.CREATE), true,
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(short) 20, DEFAULT_BLOCK_SIZE, null, false);
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//test chooseTarget for new file
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LocatedBlock locatedBlock = nameNodeRpc.addBlock(src, clientMachine,
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null, null, fileStatus.getFileId(), null);
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doTestLocatedBlock(20, locatedBlock);
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DatanodeInfo[] locs = locatedBlock.getLocations();
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String[] storageIDs = locatedBlock.getStorageIDs();
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for (int time = 0; time < 5; time++) {
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shuffle(locs, storageIDs);
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for (int i = 1; i < locs.length; i++) {
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DatanodeInfo[] partLocs = new DatanodeInfo[i];
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String[] partStorageIDs = new String[i];
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System.arraycopy(locs, 0, partLocs, 0, i);
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System.arraycopy(storageIDs, 0, partStorageIDs, 0, i);
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for (int j = 1; j < 20 - i; j++) {
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LocatedBlock additionalLocatedBlock =
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nameNodeRpc.getAdditionalDatanode(src, fileStatus.getFileId(),
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locatedBlock.getBlock(), partLocs,
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partStorageIDs, new DatanodeInfo[0],
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j, clientMachine);
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doTestLocatedBlock(i + j, additionalLocatedBlock);
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}
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}
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}
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}
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private void shuffle(DatanodeInfo[] locs, String[] storageIDs) {
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int length = locs.length;
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Object[][] pairs = new Object[length][];
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for (int i = 0; i < length; i++) {
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pairs[i] = new Object[]{locs[i], storageIDs[i]};
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}
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DFSUtil.shuffle(pairs);
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for (int i = 0; i < length; i++) {
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locs[i] = (DatanodeInfo) pairs[i][0];
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storageIDs[i] = (String) pairs[i][1];
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}
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}
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private void doTestLocatedBlock(int replication, LocatedBlock locatedBlock) {
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assertEquals(replication, locatedBlock.getLocations().length);
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HashMap<String, Integer> racksCount = new HashMap<String, Integer>();
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for (DatanodeInfo node :
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locatedBlock.getLocations()) {
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addToRacksCount(node.getNetworkLocation(), racksCount);
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}
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int minCount = Integer.MAX_VALUE;
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int maxCount = Integer.MIN_VALUE;
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for (Integer rackCount : racksCount.values()) {
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minCount = Math.min(minCount, rackCount);
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maxCount = Math.max(maxCount, rackCount);
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}
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assertTrue(maxCount - minCount <= 1);
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}
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private void addToRacksCount(String rack, HashMap<String, Integer> racksCount) {
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Integer count = racksCount.get(rack);
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if (count == null) {
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racksCount.put(rack, 1);
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} else {
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racksCount.put(rack, count + 1);
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}
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}
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}
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