Java tutorial
/** * Copyright 2009 The Apache Software Foundation * * 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 com.ci.backports.hadoop.hbase; import java.io.IOException; import java.net.URI; import java.net.URISyntaxException; import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.TreeMap; import java.util.TreeSet; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.filecache.DistributedCache; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.hbase.HConstants; import org.apache.hadoop.hbase.KeyValue; import org.apache.hadoop.hbase.client.HTable; import org.apache.hadoop.hbase.client.Put; import org.apache.hadoop.hbase.io.ImmutableBytesWritable; import org.apache.hadoop.hbase.io.hfile.Compression; import org.apache.hadoop.hbase.io.hfile.HFile; import org.apache.hadoop.hbase.mapreduce.hadoopbackport.TotalOrderPartitioner; import org.apache.hadoop.hbase.regionserver.StoreFile; import org.apache.hadoop.hbase.util.Bytes; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.SequenceFile; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.RecordWriter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.hbase.mapreduce.KeyValueSortReducer; /** * Writes HFiles. Passed KeyValues must arrive in order. * Currently, can only write files to a single column family at a * time. Multiple column families requires coordinating keys cross family. * Writes current time as the sequence id for the file. Sets the major compacted * attribute on created hfiles. Calling write(null,null) will forceably roll * all HFiles being written. * @see KeyValueSortReducer */ public class ZHFileOutputFormat extends FileOutputFormat<ImmutableBytesWritable, KeyValue> { static Log LOG = LogFactory.getLog(ZHFileOutputFormat.class); public RecordWriter<ImmutableBytesWritable, KeyValue> getRecordWriter(final TaskAttemptContext context) throws IOException, InterruptedException { // Get the path of the temporary output file final Path outputPath = FileOutputFormat.getOutputPath(context); final Path outputdir = new FileOutputCommitter(outputPath, context).getWorkPath(); Configuration conf = context.getConfiguration(); final FileSystem fs = outputdir.getFileSystem(conf); // These configs. are from hbase-*.xml final long maxsize = conf.getLong("hbase.hregion.max.filesize", HConstants.DEFAULT_MAX_FILE_SIZE); final int blocksize = conf.getInt("hfile.min.blocksize.size", HFile.DEFAULT_BLOCKSIZE); // Invented config. Add to hbase-*.xml if other than default compression. final String compression = conf.get("hfile.compression", Compression.Algorithm.NONE.getName()); return new RecordWriter<ImmutableBytesWritable, KeyValue>() { // Map of families to writers and how much has been output on the writer. private final Map<byte[], WriterLength> writers = new TreeMap<byte[], WriterLength>( Bytes.BYTES_COMPARATOR); private byte[] previousRow = HConstants.EMPTY_BYTE_ARRAY; private final byte[] now = Bytes.toBytes(System.currentTimeMillis()); private boolean rollRequested = false; public void write(ImmutableBytesWritable row, KeyValue kv) throws IOException { // null input == user explicitly wants to flush if (row == null && kv == null) { rollWriters(); return; } byte[] rowKey = kv.getRow(); long length = kv.getLength(); byte[] family = kv.getFamily(); WriterLength wl = this.writers.get(family); // If this is a new column family, verify that the directory exists if (wl == null) { fs.mkdirs(new Path(outputdir, Bytes.toString(family))); } // If any of the HFiles for the column families has reached // maxsize, we need to roll all the writers if (wl != null && wl.written + length >= maxsize) { this.rollRequested = true; } // This can only happen once a row is finished though if (rollRequested && Bytes.compareTo(this.previousRow, rowKey) != 0) { rollWriters(); } // create a new HLog writer, if necessary if (wl == null || wl.writer == null) { wl = getNewWriter(family); } // we now have the proper HLog writer. full steam ahead kv.updateLatestStamp(this.now); wl.writer.append(kv); wl.written += length; // Copy the row so we know when a row transition. this.previousRow = rowKey; } private void rollWriters() throws IOException { for (WriterLength wl : this.writers.values()) { if (wl.writer != null) { LOG.info("Writer=" + wl.writer.getPath() + ((wl.written == 0) ? "" : ", wrote=" + wl.written)); close(wl.writer); } wl.writer = null; wl.written = 0; } this.rollRequested = false; } /* Create a new HFile.Writer. * @param family * @return A WriterLength, containing a new HFile.Writer. * @throws IOException */ private WriterLength getNewWriter(byte[] family) throws IOException { WriterLength wl = new WriterLength(); Path familydir = new Path(outputdir, Bytes.toString(family)); wl.writer = new HFile.Writer(fs, StoreFile.getUniqueFile(fs, familydir), blocksize, compression, KeyValue.KEY_COMPARATOR); this.writers.put(family, wl); return wl; } private void close(final HFile.Writer w) throws IOException { if (w != null) { w.appendFileInfo(StoreFile.BULKLOAD_TIME_KEY, Bytes.toBytes(System.currentTimeMillis())); w.appendFileInfo(StoreFile.BULKLOAD_TASK_KEY, Bytes.toBytes(context.getTaskAttemptID().toString())); w.appendFileInfo(StoreFile.MAJOR_COMPACTION_KEY, Bytes.toBytes(true)); w.close(); } } public void close(TaskAttemptContext c) throws IOException, InterruptedException { for (WriterLength wl : this.writers.values()) { close(wl.writer); } } }; } /* * Data structure to hold a Writer and amount of data written on it. */ static class WriterLength { long written = 0; HFile.Writer writer = null; } /** * Return the start keys of all of the regions in this table, * as a list of ImmutableBytesWritable. */ private static List<ImmutableBytesWritable> getRegionStartKeys(HTable table) throws IOException { byte[][] byteKeys = table.getStartKeys(); ArrayList<ImmutableBytesWritable> ret = new ArrayList<ImmutableBytesWritable>(byteKeys.length); for (byte[] byteKey : byteKeys) { ret.add(new ImmutableBytesWritable(byteKey)); } return ret; } /** * Write out a SequenceFile that can be read by TotalOrderPartitioner * that contains the split points in startKeys. * @param partitionsPath output path for SequenceFile * @param startKeys the region start keys */ private static void writePartitions(Configuration conf, Path partitionsPath, List<ImmutableBytesWritable> startKeys) throws IOException { if (startKeys.isEmpty()) { throw new IllegalArgumentException("No regions passed"); } // We're generating a list of split points, and we don't ever // have keys < the first region (which has an empty start key) // so we need to remove it. Otherwise we would end up with an // empty reducer with index 0 TreeSet<ImmutableBytesWritable> sorted = new TreeSet<ImmutableBytesWritable>(startKeys); ImmutableBytesWritable first = sorted.first(); if (!first.equals(HConstants.EMPTY_BYTE_ARRAY)) { throw new IllegalArgumentException("First region of table should have empty start key. Instead has: " + Bytes.toStringBinary(first.get())); } sorted.remove(first); // Write the actual file FileSystem fs = partitionsPath.getFileSystem(conf); SequenceFile.Writer writer = SequenceFile.createWriter(fs, conf, partitionsPath, ImmutableBytesWritable.class, NullWritable.class); try { for (ImmutableBytesWritable startKey : sorted) { writer.append(startKey, NullWritable.get()); } } finally { writer.close(); } } /** * Configure a MapReduce Job to perform an incremental load into the given * table. This * <ul> * <li>Inspects the table to configure a total order partitioner</li> * <li>Uploads the partitions file to the cluster and adds it to the DistributedCache</li> * <li>Sets the number of reduce tasks to match the current number of regions</li> * <li>Sets the output key/value class to match ZHFileOutputFormat's requirements</li> * <li>Sets the reducer up to perform the appropriate sorting (either KeyValueSortReducer or * ZPutSortReducer)</li> * </ul> * The user should be sure to set the map output value class to either KeyValue or Put before * running this function. */ public static void configureIncrementalLoad(Job job, HTable table) throws IOException { Configuration conf = job.getConfiguration(); job.setPartitionerClass(TotalOrderPartitioner.class); job.setOutputKeyClass(ImmutableBytesWritable.class); job.setOutputValueClass(KeyValue.class); job.setOutputFormatClass(ZHFileOutputFormat.class); // Based on the configured map output class, set the correct reducer to properly // sort the incoming values. // TODO it would be nice to pick one or the other of these formats. if (KeyValue.class.equals(job.getMapOutputValueClass())) { job.setReducerClass(KeyValueSortReducer.class); } else if (Put.class.equals(job.getMapOutputValueClass())) { job.setReducerClass(ZPutSortReducer.class); } else { LOG.warn("Unknown map output value type:" + job.getMapOutputValueClass()); } LOG.info("Looking up current regions for table " + table); List<ImmutableBytesWritable> startKeys = getRegionStartKeys(table); LOG.info("Configuring " + startKeys.size() + " reduce partitions " + "to match current region count"); job.setNumReduceTasks(startKeys.size()); Path partitionsPath = new Path(job.getWorkingDirectory(), "partitions_" + System.currentTimeMillis()); LOG.info("Writing partition information to " + partitionsPath); FileSystem fs = partitionsPath.getFileSystem(conf); writePartitions(conf, partitionsPath, startKeys); partitionsPath.makeQualified(fs); URI cacheUri; try { cacheUri = new URI(partitionsPath.toString() + "#" + TotalOrderPartitioner.DEFAULT_PATH); } catch (URISyntaxException e) { throw new IOException(e); } DistributedCache.addCacheFile(cacheUri, conf); DistributedCache.createSymlink(conf); LOG.info("Incremental table output configured."); } }