Java tutorial
/** * 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.hama.bsp; import java.io.IOException; import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.BlockLocation; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.FileUtil; import org.apache.hadoop.fs.Path; import org.apache.hadoop.fs.PathFilter; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import org.apache.hadoop.net.NetworkTopology; import org.apache.hadoop.net.NodeBase; /** * An abstract {@link org.apache.hadoop.mapred.InputFormat}. Splits are * constructed from the files under the input paths. A split cannot have files * from different pools. Each split returned may contain blocks from different * files. If a maxSplitSize is specified, then blocks on the same node are * combined to form a single split. Blocks that are left over are then combined * with other blocks in the same rack. If maxSplitSize is not specified, then * blocks from the same rack are combined in a single split; no attempt is made * to create node-local splits. If the maxSplitSize is equal to the block size, * then this class is similar to the default spliting behaviour in Hadoop: each * block is a locally processed split. Subclasses implement * {@link org.apache.hadoop.mapred.InputFormat#getRecordReader(InputSplit, JobConf, Reporter)} * to construct <code>RecordReader</code>'s for <code>CombineFileSplit</code>'s. * * @see CombineFileSplit */ public abstract class CombineFileInputFormat<K, V> extends FileInputFormat<K, V> { // ability to limit the size of a single split private long maxSplitSize = 0; private long minSplitSizeNode = 0; private long minSplitSizeRack = 0; // A pool of input paths filters. A split cannot have blocks from files // across multiple pools. private ArrayList<MultiPathFilter> pools = new ArrayList<MultiPathFilter>(); // mapping from a rack name to the set of Nodes in the rack private static HashMap<String, Set<String>> rackToNodes = new HashMap<String, Set<String>>(); /** * This has to be overridden from concrete formats, we provide a SequenceFile * version of it for partitioning. * * @param split * @param context * @return a {@link RecordReader} to read the input for processing. * @throws IOException */ public abstract RecordReader<K, V> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException; /** * Specify the maximum size (in bytes) of each split. Each split is * approximately equal to the specified size. */ protected void setMaxSplitSize(long maxSplitSize) { this.maxSplitSize = maxSplitSize; } /** * Specify the minimum size (in bytes) of each split per node. This applies to * data that is left over after combining data on a single node into splits * that are of maximum size specified by maxSplitSize. This leftover data will * be combined into its own split if its size exceeds minSplitSizeNode. */ protected void setMinSplitSizeNode(long minSplitSizeNode) { this.minSplitSizeNode = minSplitSizeNode; } /** * Specify the minimum size (in bytes) of each split per rack. This applies to * data that is left over after combining data on a single rack into splits * that are of maximum size specified by maxSplitSize. This leftover data will * be combined into its own split if its size exceeds minSplitSizeRack. */ protected void setMinSplitSizeRack(long minSplitSizeRack) { this.minSplitSizeRack = minSplitSizeRack; } /** * Create a new pool and add the filters to it. A split cannot have files from * different pools. */ protected void createPool(Configuration conf, List<PathFilter> filters) { pools.add(new MultiPathFilter(filters)); } /** * Create a new pool and add the filters to it. A pathname can satisfy any one * of the specified filters. A split cannot have files from different pools. */ protected void createPool(Configuration conf, PathFilter... filters) { MultiPathFilter multi = new MultiPathFilter(); for (PathFilter f : filters) { multi.add(f); } pools.add(multi); } /** * default constructor */ public CombineFileInputFormat() { } @Override public InputSplit[] getSplits(BSPJob bspJob, int numSplits) throws IOException { Configuration job = bspJob.getConfiguration(); long minSizeNode = 0; long minSizeRack = 0; long maxSize = 0; // the values specified by setxxxSplitSize() takes precedence over the // values that might have been specified in the config if (minSplitSizeNode != 0) { minSizeNode = minSplitSizeNode; } else { minSizeNode = job.getLong("mapred.min.split.size.per.node", 0); } if (minSplitSizeRack != 0) { minSizeRack = minSplitSizeRack; } else { minSizeRack = job.getLong("mapred.min.split.size.per.rack", 0); } if (maxSplitSize != 0) { maxSize = maxSplitSize; } else { maxSize = job.getLong("mapred.max.split.size", 0); } if (minSizeNode != 0 && maxSize != 0 && minSizeNode > maxSize) { throw new IOException("Minimum split size pernode " + minSizeNode + " cannot be larger than maximum split size " + maxSize); } if (minSizeRack != 0 && maxSize != 0 && minSizeRack > maxSize) { throw new IOException("Minimum split size per rack" + minSizeRack + " cannot be larger than maximum split size " + maxSize); } if (minSizeRack != 0 && minSizeNode > minSizeRack) { throw new IOException("Minimum split size per node" + minSizeNode + " cannot be smaller than minimum split size per rack " + minSizeRack); } // all the files in input set Path[] paths = FileUtil.stat2Paths(listStatus(bspJob)); List<CombineFileSplit> splits = new ArrayList<CombineFileSplit>(); if (paths.length == 0) { return splits.toArray(new CombineFileSplit[splits.size()]); } // In one single iteration, process all the paths in a single pool. // Processing one pool at a time ensures that a split contans paths // from a single pool only. for (MultiPathFilter onepool : pools) { ArrayList<Path> myPaths = new ArrayList<Path>(); // pick one input path. If it matches all the filters in a pool, // add it to the output set for (int i = 0; i < paths.length; i++) { if (paths[i] == null) { // already processed continue; } Path p = new Path(paths[i].toUri().getPath()); if (onepool.accept(p)) { myPaths.add(paths[i]); // add it to my output set paths[i] = null; // already processed } } // create splits for all files in this pool. getMoreSplits(bspJob, myPaths.toArray(new Path[myPaths.size()]), maxSize, minSizeNode, minSizeRack, splits); } // Finally, process all paths that do not belong to any pool. ArrayList<Path> myPaths = new ArrayList<Path>(); for (Path path : paths) { if (path == null) { // already processed continue; } myPaths.add(path); } // create splits for all files that are not in any pool. getMoreSplits(bspJob, myPaths.toArray(new Path[myPaths.size()]), maxSize, minSizeNode, minSizeRack, splits); // free up rackToNodes map rackToNodes.clear(); return splits.toArray(new CombineFileSplit[splits.size()]); } /** * Return all the splits in the specified set of paths */ private static void getMoreSplits(BSPJob job, Path[] paths, long maxSize, long minSizeNode, long minSizeRack, List<CombineFileSplit> splits) throws IOException { // all blocks for all the files in input set OneFileInfo[] files; // mapping from a rack name to the list of blocks it has HashMap<String, List<OneBlockInfo>> rackToBlocks = new HashMap<String, List<OneBlockInfo>>(); // mapping from a block to the nodes on which it has replicas HashMap<OneBlockInfo, String[]> blockToNodes = new HashMap<OneBlockInfo, String[]>(); // mapping from a node to the list of blocks that it contains HashMap<String, List<OneBlockInfo>> nodeToBlocks = new HashMap<String, List<OneBlockInfo>>(); files = new OneFileInfo[paths.length]; if (paths.length == 0) { return; } // populate all the blocks for all files for (int i = 0; i < paths.length; i++) { files[i] = new OneFileInfo(paths[i], job, rackToBlocks, blockToNodes, nodeToBlocks); } ArrayList<OneBlockInfo> validBlocks = new ArrayList<OneBlockInfo>(); ArrayList<String> nodes = new ArrayList<String>(); long curSplitSize = 0; // process all nodes and create splits that are local // to a node. for (Map.Entry<String, List<OneBlockInfo>> one : nodeToBlocks.entrySet()) { nodes.add(one.getKey()); List<OneBlockInfo> blocksInNode = one.getValue(); // for each block, copy it into validBlocks. Delete it from // blockToNodes so that the same block does not appear in // two different splits. for (OneBlockInfo oneblock : blocksInNode) { if (blockToNodes.containsKey(oneblock)) { validBlocks.add(oneblock); blockToNodes.remove(oneblock); curSplitSize += oneblock.length; // if the accumulated split size exceeds the maximum, then // create this split. if (maxSize != 0 && curSplitSize >= maxSize) { // create an input split and add it to the splits array addCreatedSplit(job, splits, nodes, validBlocks); curSplitSize = 0; validBlocks.clear(); } } } // if there were any blocks left over and their combined size is // larger than minSplitNode, then combine them into one split. // Otherwise add them back to the unprocessed pool. It is likely // that they will be combined with other blocks from the same rack later // on. if (minSizeNode != 0 && curSplitSize >= minSizeNode) { // create an input split and add it to the splits array addCreatedSplit(job, splits, nodes, validBlocks); } else { for (OneBlockInfo oneblock : validBlocks) { blockToNodes.put(oneblock, oneblock.hosts); } } validBlocks.clear(); nodes.clear(); curSplitSize = 0; } // if blocks in a rack are below the specified minimum size, then keep them // in 'overflow'. After the processing of all racks is complete, these // overflow // blocks will be combined into splits. ArrayList<OneBlockInfo> overflowBlocks = new ArrayList<OneBlockInfo>(); ArrayList<String> racks = new ArrayList<String>(); // Process all racks over and over again until there is no more work to do. while (blockToNodes.size() > 0) { // Create one split for this rack before moving over to the next rack. // Come back to this rack after creating a single split for each of the // remaining racks. // Process one rack location at a time, Combine all possible blocks that // reside on this rack as one split. (constrained by minimum and maximum // split size). // iterate over all racks for (Map.Entry<String, List<OneBlockInfo>> one : rackToBlocks.entrySet()) { racks.add(one.getKey()); List<OneBlockInfo> blocks = one.getValue(); // for each block, copy it into validBlocks. Delete it from // blockToNodes so that the same block does not appear in // two different splits. boolean createdSplit = false; for (OneBlockInfo oneblock : blocks) { if (blockToNodes.containsKey(oneblock)) { validBlocks.add(oneblock); blockToNodes.remove(oneblock); curSplitSize += oneblock.length; // if the accumulated split size exceeds the maximum, then // create this split. if (maxSize != 0 && curSplitSize >= maxSize) { // create an input split and add it to the splits array addCreatedSplit(job, splits, getHosts(racks), validBlocks); createdSplit = true; break; } } } // if we created a split, then just go to the next rack if (createdSplit) { curSplitSize = 0; validBlocks.clear(); racks.clear(); continue; } if (!validBlocks.isEmpty()) { if (minSizeRack != 0 && curSplitSize >= minSizeRack) { // if there is a mimimum size specified, then create a single split // otherwise, store these blocks into overflow data structure addCreatedSplit(job, splits, getHosts(racks), validBlocks); } else { // There were a few blocks in this rack that remained to be // processed. // Keep them in 'overflow' block list. These will be combined later. overflowBlocks.addAll(validBlocks); } } curSplitSize = 0; validBlocks.clear(); racks.clear(); } } assert blockToNodes.isEmpty(); assert curSplitSize == 0; assert validBlocks.isEmpty(); assert racks.isEmpty(); // Process all overflow blocks for (OneBlockInfo oneblock : overflowBlocks) { validBlocks.add(oneblock); curSplitSize += oneblock.length; // This might cause an exiting rack location to be re-added, // but it should be ok. Collections.addAll(racks, oneblock.racks); // if the accumulated split size exceeds the maximum, then // create this split. if (maxSize != 0 && curSplitSize >= maxSize) { // create an input split and add it to the splits array addCreatedSplit(job, splits, getHosts(racks), validBlocks); curSplitSize = 0; validBlocks.clear(); racks.clear(); } } // Process any remaining blocks, if any. if (!validBlocks.isEmpty()) { addCreatedSplit(job, splits, getHosts(racks), validBlocks); } } /** * Create a single split from the list of blocks specified in validBlocks Add * this new split into splitList. */ private static void addCreatedSplit(BSPJob job, List<CombineFileSplit> splitList, List<String> locations, ArrayList<OneBlockInfo> validBlocks) { // create an input split Path[] fl = new Path[validBlocks.size()]; long[] offset = new long[validBlocks.size()]; long[] length = new long[validBlocks.size()]; for (int i = 0; i < validBlocks.size(); i++) { fl[i] = validBlocks.get(i).onepath; offset[i] = validBlocks.get(i).offset; length[i] = validBlocks.get(i).length; } // add this split to the list that is returned CombineFileSplit thissplit = new CombineFileSplit(job, fl, offset, length, locations.toArray(new String[locations.size()])); splitList.add(thissplit); } /** * information about one file from the File System */ private static class OneFileInfo { private long fileSize; // size of the file private OneBlockInfo[] blocks; // all blocks in this file OneFileInfo(Path path, BSPJob job, HashMap<String, List<OneBlockInfo>> rackToBlocks, HashMap<OneBlockInfo, String[]> blockToNodes, HashMap<String, List<OneBlockInfo>> nodeToBlocks) throws IOException { this.fileSize = 0; // get block locations from file system FileSystem fs = path.getFileSystem(job.getConfiguration()); FileStatus stat = fs.getFileStatus(path); BlockLocation[] locations = fs.getFileBlockLocations(stat, 0, stat.getLen()); // create a list of all block and their locations if (locations == null) { blocks = new OneBlockInfo[0]; } else { blocks = new OneBlockInfo[locations.length]; for (int i = 0; i < locations.length; i++) { fileSize += locations[i].getLength(); OneBlockInfo oneblock = new OneBlockInfo(path, locations[i].getOffset(), locations[i].getLength(), locations[i].getHosts(), locations[i].getTopologyPaths()); blocks[i] = oneblock; // add this block to the block --> node locations map blockToNodes.put(oneblock, oneblock.hosts); // add this block to the rack --> block map for (int j = 0; j < oneblock.racks.length; j++) { String rack = oneblock.racks[j]; List<OneBlockInfo> blklist = rackToBlocks.get(rack); if (blklist == null) { blklist = new ArrayList<OneBlockInfo>(); rackToBlocks.put(rack, blklist); } blklist.add(oneblock); // Add this host to rackToNodes map addHostToRack(oneblock.racks[j], oneblock.hosts[j]); } // add this block to the node --> block map for (int j = 0; j < oneblock.hosts.length; j++) { String node = oneblock.hosts[j]; List<OneBlockInfo> blklist = nodeToBlocks.get(node); if (blklist == null) { blklist = new ArrayList<OneBlockInfo>(); nodeToBlocks.put(node, blklist); } blklist.add(oneblock); } } } } } /** * information about one block from the File System */ private static class OneBlockInfo { Path onepath; // name of this file long offset; // offset in file long length; // length of this block String[] hosts; // nodes on whch this block resides String[] racks; // network topology of hosts OneBlockInfo(Path path, long offset, long len, String[] hosts, String[] pTopologyPaths) { String[] topologyPaths = pTopologyPaths; this.onepath = path; this.offset = offset; this.hosts = hosts; this.length = len; assert (hosts.length == topologyPaths.length || topologyPaths.length == 0); // if the file ystem does not have any rack information, then // use dummy rack location. if (topologyPaths.length == 0) { topologyPaths = new String[hosts.length]; for (int i = 0; i < topologyPaths.length; i++) { topologyPaths[i] = (new NodeBase(hosts[i], NetworkTopology.DEFAULT_RACK)).toString(); } } // The topology paths have the host name included as the last // component. Strip it. this.racks = new String[topologyPaths.length]; for (int i = 0; i < topologyPaths.length; i++) { this.racks[i] = (new NodeBase(topologyPaths[i])).getNetworkLocation(); } } } private static void addHostToRack(String rack, String host) { Set<String> hosts = rackToNodes.get(rack); if (hosts == null) { hosts = new HashSet<String>(); rackToNodes.put(rack, hosts); } hosts.add(host); } private static List<String> getHosts(List<String> racks) { List<String> hosts = new ArrayList<String>(); for (String rack : racks) { hosts.addAll(rackToNodes.get(rack)); } return hosts; } /** * Accept a path only if any one of filters given in the constructor do. */ private static class MultiPathFilter implements PathFilter { private List<PathFilter> filters; public MultiPathFilter() { this.filters = new ArrayList<PathFilter>(); } public MultiPathFilter(List<PathFilter> filters) { this.filters = filters; } public void add(PathFilter one) { filters.add(one); } @Override public boolean accept(Path path) { for (PathFilter filter : filters) { if (filter.accept(path)) { return true; } } return false; } @Override public String toString() { StringBuffer buf = new StringBuffer(); buf.append("["); for (PathFilter f : filters) { buf.append(f); buf.append(","); } buf.append("]"); return buf.toString(); } } }