/**
* 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.tools.mapred.lib;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.tools.CopyListingFileStatus;
import org.apache.hadoop.tools.DistCpConstants;
import org.apache.hadoop.tools.util.DistCpUtils;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileRecordReader;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskID;
import java.io.IOException;
/**
* The DynamicInputChunk represents a single chunk of work, when used in
* conjunction with the DynamicInputFormat and the DynamicRecordReader.
* The records in the DynamicInputFormat's input-file are split across various
* DynamicInputChunks. Each one is claimed and processed in an iteration of
* a dynamic-mapper. When a DynamicInputChunk has been exhausted, the faster
* mapper may claim another and process it, until there are no more to be
* consumed.
*/
class DynamicInputChunk<K, V> {
private static Log LOG = LogFactory.getLog(DynamicInputChunk.class);
private static Configuration configuration;
private static Path chunkRootPath;
private static String chunkFilePrefix;
private static int numChunksLeft = -1; // Un-initialized before 1st dir-scan.
private static FileSystem fs;
private Path chunkFilePath;
private SequenceFileRecordReader<K, V> reader;
private SequenceFile.Writer writer;
private static void initializeChunkInvariants(Configuration config)
throws IOException {
configuration = config;
Path listingFilePath = new Path(getListingFilePath(configuration));
chunkRootPath = new Path(listingFilePath.getParent(), "chunkDir");
fs = chunkRootPath.getFileSystem(configuration);
chunkFilePrefix = listingFilePath.getName() + ".chunk.";
}
private static String getListingFilePath(Configuration configuration) {
final String listingFileString = configuration.get(
DistCpConstants.CONF_LABEL_LISTING_FILE_PATH, "");
assert !listingFileString.equals("") : "Listing file not found.";
return listingFileString;
}
private static boolean areInvariantsInitialized() {
return chunkRootPath != null;
}
private DynamicInputChunk(String chunkId, Configuration configuration)
throws IOException {
if (!areInvariantsInitialized())
initializeChunkInvariants(configuration);
chunkFilePath = new Path(chunkRootPath, chunkFilePrefix + chunkId);
openForWrite();
}
private void openForWrite() throws IOException {
writer = SequenceFile.createWriter(
chunkFilePath.getFileSystem(configuration), configuration,
chunkFilePath, Text.class, CopyListingFileStatus.class,
SequenceFile.CompressionType.NONE);
}
/**
* Factory method to create chunk-files for writing to.
* (For instance, when the DynamicInputFormat splits the input-file into
* chunks.)
* @param chunkId String to identify the chunk.
* @param configuration Configuration, describing the location of the listing-
* file, file-system for the map-job, etc.
* @return A DynamicInputChunk, corresponding to a chunk-file, with the name
* incorporating the chunk-id.
* @throws IOException Exception on failure to create the chunk.
*/
public static DynamicInputChunk createChunkForWrite(String chunkId,
Configuration configuration) throws IOException {
return new DynamicInputChunk(chunkId, configuration);
}
/**
* Method to write records into a chunk.
* @param key Key from the listing file.
* @param value Corresponding value from the listing file.
* @throws IOException Exception onf failure to write to the file.
*/
public void write(Text key, CopyListingFileStatus value) throws IOException {
writer.append(key, value);
}
/**
* Closes streams opened to the chunk-file.
*/
public void close() {
IOUtils.cleanup(LOG, reader, writer);
}
/**
* Reassigns the chunk to a specified Map-Task, for consumption.
* @param taskId The Map-Task to which a the chunk is to be reassigned.
* @throws IOException Exception on failure to reassign.
*/
public void assignTo(TaskID taskId) throws IOException {
Path newPath = new Path(chunkRootPath, taskId.toString());
if (!fs.rename(chunkFilePath, newPath)) {
LOG.warn(chunkFilePath + " could not be assigned to " + taskId);
}
}
private DynamicInputChunk(Path chunkFilePath,
TaskAttemptContext taskAttemptContext)
throws IOException, InterruptedException {
if (!areInvariantsInitialized())
initializeChunkInvariants(taskAttemptContext.getConfiguration());
this.chunkFilePath = chunkFilePath;
openForRead(taskAttemptContext);
}
private void openForRead(TaskAttemptContext taskAttemptContext)
throws IOException, InterruptedException {
reader = new SequenceFileRecordReader<K, V>();
reader.initialize(new FileSplit(chunkFilePath, 0,
DistCpUtils.getFileSize(chunkFilePath, configuration), null),
taskAttemptContext);
}
/**
* Factory method that
* 1. acquires a chunk for the specified map-task attempt
* 2. returns a DynamicInputChunk associated with the acquired chunk-file.
* @param taskAttemptContext The attempt-context for the map task that's
* trying to acquire a chunk.
* @return The acquired dynamic-chunk. The chunk-file is renamed to the
* attempt-id (from the attempt-context.)
* @throws IOException Exception on failure.
* @throws InterruptedException Exception on failure.
*/
public static DynamicInputChunk acquire(TaskAttemptContext taskAttemptContext)
throws IOException, InterruptedException {
if (!areInvariantsInitialized())
initializeChunkInvariants(taskAttemptContext.getConfiguration());
String taskId
= taskAttemptContext.getTaskAttemptID().getTaskID().toString();
Path acquiredFilePath = new Path(chunkRootPath, taskId);
if (fs.exists(acquiredFilePath)) {
LOG.info("Acquiring pre-assigned chunk: " + acquiredFilePath);
return new DynamicInputChunk(acquiredFilePath, taskAttemptContext);
}
for (FileStatus chunkFile : getListOfChunkFiles()) {
if (fs.rename(chunkFile.getPath(), acquiredFilePath)) {
LOG.info(taskId + " acquired " + chunkFile.getPath());
return new DynamicInputChunk(acquiredFilePath, taskAttemptContext);
}
else
LOG.warn(taskId + " could not acquire " + chunkFile.getPath());
}
return null;
}
/**
* Method to be called to relinquish an acquired chunk. All streams open to
* the chunk are closed, and the chunk-file is deleted.
* @throws IOException Exception thrown on failure to release (i.e. delete)
* the chunk file.
*/
public void release() throws IOException {
close();
if (!fs.delete(chunkFilePath, false)) {
LOG.error("Unable to release chunk at path: " + chunkFilePath);
throw new IOException("Unable to release chunk at path: " + chunkFilePath);
}
}
static FileStatus [] getListOfChunkFiles() throws IOException {
Path chunkFilePattern = new Path(chunkRootPath, chunkFilePrefix + "*");
FileStatus chunkFiles[] = fs.globStatus(chunkFilePattern);
numChunksLeft = chunkFiles.length;
return chunkFiles;
}
/**
* Getter for the chunk-file's path, on HDFS.
* @return The qualified path to the chunk-file.
*/
public Path getPath() {
return chunkFilePath;
}
/**
* Getter for the record-reader, opened to the chunk-file.
* @return Opened Sequence-file reader.
*/
public SequenceFileRecordReader<K,V> getReader() {
assert reader != null : "Reader un-initialized!";
return reader;
}
/**
* Getter for the number of chunk-files left in the chunk-file directory.
* Useful to determine how many chunks (and hence, records) are left to be
* processed.
* @return Before the first scan of the directory, the number returned is -1.
* Otherwise, the number of chunk-files seen from the last scan is returned.
*/
public static int getNumChunksLeft() {
return numChunksLeft;
}
}