/**
* 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.mapred.lib;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.util.Progressable;
import java.io.IOException;
import java.util.*;
/**
* The MultipleOutputs class simplifies writting to additional outputs other
* than the job default output via the <code>OutputCollector</code> passed to
* the <code>map()</code> and <code>reduce()</code> methods of the
* <code>Mapper</code> and <code>Reducer</code> implementations.
* <p/>
* Each additional output, or named output, may be configured with its own
* <code>OutputFormat</code>, with its own key class and with its own value
* class.
* <p/>
* A named output can be a single file or a multi file. The later is refered as
* a multi named output.
* <p/>
* A multi named output is an unbound set of files all sharing the same
* <code>OutputFormat</code>, key class and value class configuration.
* <p/>
* When named outputs are used within a <code>Mapper</code> implementation,
* key/values written to a name output are not part of the reduce phase, only
* key/values written to the job <code>OutputCollector</code> are part of the
* reduce phase.
* <p/>
* MultipleOutputs supports counters, by default the are disabled. The counters
* group is the {@link MultipleOutputs} class name.
* </p>
* The names of the counters are the same as the named outputs. For multi
* named outputs the name of the counter is the concatenation of the named
* output, and underscore '_' and the multiname.
* <p/>
* Job configuration usage pattern is:
* <pre>
*
* JobConf conf = new JobConf();
*
* conf.setInputPath(inDir);
* FileOutputFormat.setOutputPath(conf, outDir);
*
* conf.setMapperClass(MOMap.class);
* conf.setReducerClass(MOReduce.class);
* ...
*
* // Defines additional single text based output 'text' for the job
* MultipleOutputs.addNamedOutput(conf, "text", TextOutputFormat.class,
* LongWritable.class, Text.class);
*
* // Defines additional multi sequencefile based output 'sequence' for the
* // job
* MultipleOutputs.addMultiNamedOutput(conf, "seq",
* SequenceFileOutputFormat.class,
* LongWritable.class, Text.class);
* ...
*
* JobClient jc = new JobClient();
* RunningJob job = jc.submitJob(conf);
*
* ...
* </pre>
* <p/>
* Job configuration usage pattern is:
* <pre>
*
* public class MOReduce implements
* Reducer<WritableComparable, Writable> {
* private MultipleOutputs mos;
*
* public void configure(JobConf conf) {
* ...
* mos = new MultipleOutputs(conf);
* }
*
* public void reduce(WritableComparable key, Iterator<Writable> values,
* OutputCollector output, Reporter reporter)
* throws IOException {
* ...
* mos.getCollector("text", reporter).collect(key, new Text("Hello"));
* mos.getCollector("seq", "A", reporter).collect(key, new Text("Bye"));
* mos.getCollector("seq", "B", reporter).collect(key, new Text("Chau"));
* ...
* }
*
* public void close() throws IOException {
* mos.close();
* ...
* }
*
* }
* </pre>
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class MultipleOutputs {
private static final String NAMED_OUTPUTS = "mo.namedOutputs";
private static final String MO_PREFIX = "mo.namedOutput.";
private static final String FORMAT = ".format";
private static final String KEY = ".key";
private static final String VALUE = ".value";
private static final String MULTI = ".multi";
private static final String COUNTERS_ENABLED = "mo.counters";
/**
* Counters group used by the counters of MultipleOutputs.
*/
private static final String COUNTERS_GROUP = MultipleOutputs.class.getName();
/**
* Checks if a named output is alreadyDefined or not.
*
* @param conf job conf
* @param namedOutput named output names
* @param alreadyDefined whether the existence/non-existence of
* the named output is to be checked
* @throws IllegalArgumentException if the output name is alreadyDefined or
* not depending on the value of the
* 'alreadyDefined' parameter
*/
private static void checkNamedOutput(JobConf conf, String namedOutput,
boolean alreadyDefined) {
List<String> definedChannels = getNamedOutputsList(conf);
if (alreadyDefined && definedChannels.contains(namedOutput)) {
throw new IllegalArgumentException("Named output '" + namedOutput +
"' already alreadyDefined");
} else if (!alreadyDefined && !definedChannels.contains(namedOutput)) {
throw new IllegalArgumentException("Named output '" + namedOutput +
"' not defined");
}
}
/**
* Checks if a named output name is valid token.
*
* @param namedOutput named output Name
* @throws IllegalArgumentException if the output name is not valid.
*/
private static void checkTokenName(String namedOutput) {
if (namedOutput == null || namedOutput.length() == 0) {
throw new IllegalArgumentException(
"Name cannot be NULL or emtpy");
}
for (char ch : namedOutput.toCharArray()) {
if ((ch >= 'A') && (ch <= 'Z')) {
continue;
}
if ((ch >= 'a') && (ch <= 'z')) {
continue;
}
if ((ch >= '0') && (ch <= '9')) {
continue;
}
throw new IllegalArgumentException(
"Name cannot be have a '" + ch + "' char");
}
}
/**
* Checks if a named output name is valid.
*
* @param namedOutput named output Name
* @throws IllegalArgumentException if the output name is not valid.
*/
private static void checkNamedOutputName(String namedOutput) {
checkTokenName(namedOutput);
// name cannot be the name used for the default output
if (namedOutput.equals("part")) {
throw new IllegalArgumentException(
"Named output name cannot be 'part'");
}
}
/**
* Returns list of channel names.
*
* @param conf job conf
* @return List of channel Names
*/
public static List<String> getNamedOutputsList(JobConf conf) {
List<String> names = new ArrayList<String>();
StringTokenizer st = new StringTokenizer(conf.get(NAMED_OUTPUTS, ""), " ");
while (st.hasMoreTokens()) {
names.add(st.nextToken());
}
return names;
}
/**
* Returns if a named output is multiple.
*
* @param conf job conf
* @param namedOutput named output
* @return <code>true</code> if the name output is multi, <code>false</code>
* if it is single. If the name output is not defined it returns
* <code>false</code>
*/
public static boolean isMultiNamedOutput(JobConf conf, String namedOutput) {
checkNamedOutput(conf, namedOutput, false);
return conf.getBoolean(MO_PREFIX + namedOutput + MULTI, false);
}
/**
* Returns the named output OutputFormat.
*
* @param conf job conf
* @param namedOutput named output
* @return namedOutput OutputFormat
*/
public static Class<? extends OutputFormat> getNamedOutputFormatClass(
JobConf conf, String namedOutput) {
checkNamedOutput(conf, namedOutput, false);
return conf.getClass(MO_PREFIX + namedOutput + FORMAT, null,
OutputFormat.class);
}
/**
* Returns the key class for a named output.
*
* @param conf job conf
* @param namedOutput named output
* @return class for the named output key
*/
public static Class<?> getNamedOutputKeyClass(JobConf conf,
String namedOutput) {
checkNamedOutput(conf, namedOutput, false);
return conf.getClass(MO_PREFIX + namedOutput + KEY, null,
Object.class);
}
/**
* Returns the value class for a named output.
*
* @param conf job conf
* @param namedOutput named output
* @return class of named output value
*/
public static Class<?> getNamedOutputValueClass(JobConf conf,
String namedOutput) {
checkNamedOutput(conf, namedOutput, false);
return conf.getClass(MO_PREFIX + namedOutput + VALUE, null,
Object.class);
}
/**
* Adds a named output for the job.
* <p/>
*
* @param conf job conf to add the named output
* @param namedOutput named output name, it has to be a word, letters
* and numbers only, cannot be the word 'part' as
* that is reserved for the
* default output.
* @param outputFormatClass OutputFormat class.
* @param keyClass key class
* @param valueClass value class
*/
public static void addNamedOutput(JobConf conf, String namedOutput,
Class<? extends OutputFormat> outputFormatClass,
Class<?> keyClass, Class<?> valueClass) {
addNamedOutput(conf, namedOutput, false, outputFormatClass, keyClass,
valueClass);
}
/**
* Adds a multi named output for the job.
* <p/>
*
* @param conf job conf to add the named output
* @param namedOutput named output name, it has to be a word, letters
* and numbers only, cannot be the word 'part' as
* that is reserved for the
* default output.
* @param outputFormatClass OutputFormat class.
* @param keyClass key class
* @param valueClass value class
*/
public static void addMultiNamedOutput(JobConf conf, String namedOutput,
Class<? extends OutputFormat> outputFormatClass,
Class<?> keyClass, Class<?> valueClass) {
addNamedOutput(conf, namedOutput, true, outputFormatClass, keyClass,
valueClass);
}
/**
* Adds a named output for the job.
* <p/>
*
* @param conf job conf to add the named output
* @param namedOutput named output name, it has to be a word, letters
* and numbers only, cannot be the word 'part' as
* that is reserved for the
* default output.
* @param multi indicates if the named output is multi
* @param outputFormatClass OutputFormat class.
* @param keyClass key class
* @param valueClass value class
*/
private static void addNamedOutput(JobConf conf, String namedOutput,
boolean multi,
Class<? extends OutputFormat> outputFormatClass,
Class<?> keyClass, Class<?> valueClass) {
checkNamedOutputName(namedOutput);
checkNamedOutput(conf, namedOutput, true);
conf.set(NAMED_OUTPUTS, conf.get(NAMED_OUTPUTS, "") + " " + namedOutput);
conf.setClass(MO_PREFIX + namedOutput + FORMAT, outputFormatClass,
OutputFormat.class);
conf.setClass(MO_PREFIX + namedOutput + KEY, keyClass, Object.class);
conf.setClass(MO_PREFIX + namedOutput + VALUE, valueClass, Object.class);
conf.setBoolean(MO_PREFIX + namedOutput + MULTI, multi);
}
/**
* Enables or disables counters for the named outputs.
* <p/>
* By default these counters are disabled.
* <p/>
* MultipleOutputs supports counters, by default the are disabled.
* The counters group is the {@link MultipleOutputs} class name.
* </p>
* The names of the counters are the same as the named outputs. For multi
* named outputs the name of the counter is the concatenation of the named
* output, and underscore '_' and the multiname.
*
* @param conf job conf to enableadd the named output.
* @param enabled indicates if the counters will be enabled or not.
*/
public static void setCountersEnabled(JobConf conf, boolean enabled) {
conf.setBoolean(COUNTERS_ENABLED, enabled);
}
/**
* Returns if the counters for the named outputs are enabled or not.
* <p/>
* By default these counters are disabled.
* <p/>
* MultipleOutputs supports counters, by default the are disabled.
* The counters group is the {@link MultipleOutputs} class name.
* </p>
* The names of the counters are the same as the named outputs. For multi
* named outputs the name of the counter is the concatenation of the named
* output, and underscore '_' and the multiname.
*
*
* @param conf job conf to enableadd the named output.
* @return TRUE if the counters are enabled, FALSE if they are disabled.
*/
public static boolean getCountersEnabled(JobConf conf) {
return conf.getBoolean(COUNTERS_ENABLED, false);
}
// instance code, to be used from Mapper/Reducer code
private JobConf conf;
private OutputFormat outputFormat;
private Set<String> namedOutputs;
private Map<String, RecordWriter> recordWriters;
private boolean countersEnabled;
/**
* Creates and initializes multiple named outputs support, it should be
* instantiated in the Mapper/Reducer configure method.
*
* @param job the job configuration object
*/
public MultipleOutputs(JobConf job) {
this.conf = job;
outputFormat = new InternalFileOutputFormat();
namedOutputs = Collections.unmodifiableSet(
new HashSet<String>(MultipleOutputs.getNamedOutputsList(job)));
recordWriters = new HashMap<String, RecordWriter>();
countersEnabled = getCountersEnabled(job);
}
/**
* Returns iterator with the defined name outputs.
*
* @return iterator with the defined named outputs
*/
public Iterator<String> getNamedOutputs() {
return namedOutputs.iterator();
}
// by being synchronized MultipleOutputTask can be use with a
// MultithreaderMapRunner.
private synchronized RecordWriter getRecordWriter(String namedOutput,
String baseFileName,
final Reporter reporter)
throws IOException {
RecordWriter writer = recordWriters.get(baseFileName);
if (writer == null) {
if (countersEnabled && reporter == null) {
throw new IllegalArgumentException(
"Counters are enabled, Reporter cannot be NULL");
}
JobConf jobConf = new JobConf(conf);
jobConf.set(InternalFileOutputFormat.CONFIG_NAMED_OUTPUT, namedOutput);
FileSystem fs = FileSystem.get(conf);
writer =
outputFormat.getRecordWriter(fs, jobConf, baseFileName, reporter);
if (countersEnabled) {
if (reporter == null) {
throw new IllegalArgumentException(
"Counters are enabled, Reporter cannot be NULL");
}
writer = new RecordWriterWithCounter(writer, baseFileName, reporter);
}
recordWriters.put(baseFileName, writer);
}
return writer;
}
private static class RecordWriterWithCounter implements RecordWriter {
private RecordWriter writer;
private String counterName;
private Reporter reporter;
public RecordWriterWithCounter(RecordWriter writer, String counterName,
Reporter reporter) {
this.writer = writer;
this.counterName = counterName;
this.reporter = reporter;
}
@SuppressWarnings({"unchecked"})
public void write(Object key, Object value) throws IOException {
reporter.incrCounter(COUNTERS_GROUP, counterName, 1);
writer.write(key, value);
}
public void close(Reporter reporter) throws IOException {
writer.close(reporter);
}
}
/**
* Gets the output collector for a named output.
* <p/>
*
* @param namedOutput the named output name
* @param reporter the reporter
* @return the output collector for the given named output
* @throws IOException thrown if output collector could not be created
*/
@SuppressWarnings({"unchecked"})
public OutputCollector getCollector(String namedOutput, Reporter reporter)
throws IOException {
return getCollector(namedOutput, null, reporter);
}
/**
* Gets the output collector for a multi named output.
* <p/>
*
* @param namedOutput the named output name
* @param multiName the multi name part
* @param reporter the reporter
* @return the output collector for the given named output
* @throws IOException thrown if output collector could not be created
*/
@SuppressWarnings({"unchecked"})
public OutputCollector getCollector(String namedOutput, String multiName,
Reporter reporter)
throws IOException {
checkNamedOutputName(namedOutput);
if (!namedOutputs.contains(namedOutput)) {
throw new IllegalArgumentException("Undefined named output '" +
namedOutput + "'");
}
boolean multi = isMultiNamedOutput(conf, namedOutput);
if (!multi && multiName != null) {
throw new IllegalArgumentException("Name output '" + namedOutput +
"' has not been defined as multi");
}
if (multi) {
checkTokenName(multiName);
}
String baseFileName = (multi) ? namedOutput + "_" + multiName : namedOutput;
final RecordWriter writer =
getRecordWriter(namedOutput, baseFileName, reporter);
return new OutputCollector() {
@SuppressWarnings({"unchecked"})
public void collect(Object key, Object value) throws IOException {
writer.write(key, value);
}
};
}
/**
* Closes all the opened named outputs.
* <p/>
* If overriden subclasses must invoke <code>super.close()</code> at the
* end of their <code>close()</code>
*
* @throws java.io.IOException thrown if any of the MultipleOutput files
* could not be closed properly.
*/
public void close() throws IOException {
for (RecordWriter writer : recordWriters.values()) {
writer.close(null);
}
}
private static class InternalFileOutputFormat extends
FileOutputFormat<Object, Object> {
public static final String CONFIG_NAMED_OUTPUT = "mo.config.namedOutput";
@SuppressWarnings({"unchecked"})
public RecordWriter<Object, Object> getRecordWriter(
FileSystem fs, JobConf job, String baseFileName, Progressable progress)
throws IOException {
String nameOutput = job.get(CONFIG_NAMED_OUTPUT, null);
String fileName = getUniqueName(job, baseFileName);
// The following trick leverages the instantiation of a record writer via
// the job conf thus supporting arbitrary output formats.
JobConf outputConf = new JobConf(job);
outputConf.setOutputFormat(getNamedOutputFormatClass(job, nameOutput));
outputConf.setOutputKeyClass(getNamedOutputKeyClass(job, nameOutput));
outputConf.setOutputValueClass(getNamedOutputValueClass(job, nameOutput));
OutputFormat outputFormat = outputConf.getOutputFormat();
return outputFormat.getRecordWriter(fs, outputConf, fileName, progress);
}
}
}