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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/**
* 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.cassandra.hadoop;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Counter;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.JobID;
import org.apache.hadoop.mapreduce.MapContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.StatusReporter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.TaskInputOutputContext;
/*
* This is based on ContextFactory.java from hadoop-2.0.x sources.
*/
/**
* Utility methods to allow applications to deal with inconsistencies between
* MapReduce Context Objects API between Hadoop 1.x and 2.x.
*/
public class HadoopCompat
{
private static final boolean useV21;
private static final Constructor JOB_CONTEXT_CONSTRUCTOR;
private static final Constructor TASK_CONTEXT_CONSTRUCTOR;
private static final Constructor MAP_CONTEXT_CONSTRUCTOR;
private static final Constructor GENERIC_COUNTER_CONSTRUCTOR;
private static final Field READER_FIELD;
private static final Field WRITER_FIELD;
private static final Method GET_CONFIGURATION_METHOD;
private static final Method SET_STATUS_METHOD;
private static final Method GET_COUNTER_METHOD;
private static final Method INCREMENT_COUNTER_METHOD;
private static final Method GET_TASK_ATTEMPT_ID;
private static final Method PROGRESS_METHOD;
static
{
boolean v21 = true;
final String PACKAGE = "org.apache.hadoop.mapreduce";
try
{
Class.forName(PACKAGE + ".task.JobContextImpl");
} catch (ClassNotFoundException cnfe)
{
v21 = false;
}
useV21 = v21;
Class jobContextCls;
Class taskContextCls;
Class taskIOContextCls;
Class mapContextCls;
Class genericCounterCls;
try
{
if (v21)
{
jobContextCls =
Class.forName(PACKAGE+".task.JobContextImpl");
taskContextCls =
Class.forName(PACKAGE+".task.TaskAttemptContextImpl");
taskIOContextCls =
Class.forName(PACKAGE+".task.TaskInputOutputContextImpl");
mapContextCls = Class.forName(PACKAGE + ".task.MapContextImpl");
genericCounterCls = Class.forName(PACKAGE+".counters.GenericCounter");
}
else
{
jobContextCls =
Class.forName(PACKAGE+".JobContext");
taskContextCls =
Class.forName(PACKAGE+".TaskAttemptContext");
taskIOContextCls =
Class.forName(PACKAGE+".TaskInputOutputContext");
mapContextCls = Class.forName(PACKAGE + ".MapContext");
genericCounterCls =
Class.forName("org.apache.hadoop.mapred.Counters$Counter");
}
} catch (ClassNotFoundException e)
{
throw new IllegalArgumentException("Can't find class", e);
}
try
{
JOB_CONTEXT_CONSTRUCTOR =
jobContextCls.getConstructor(Configuration.class, JobID.class);
JOB_CONTEXT_CONSTRUCTOR.setAccessible(true);
TASK_CONTEXT_CONSTRUCTOR =
taskContextCls.getConstructor(Configuration.class,
TaskAttemptID.class);
TASK_CONTEXT_CONSTRUCTOR.setAccessible(true);
GENERIC_COUNTER_CONSTRUCTOR =
genericCounterCls.getDeclaredConstructor(String.class,
String.class,
Long.TYPE);
GENERIC_COUNTER_CONSTRUCTOR.setAccessible(true);
if (useV21)
{
MAP_CONTEXT_CONSTRUCTOR =
mapContextCls.getDeclaredConstructor(Configuration.class,
TaskAttemptID.class,
RecordReader.class,
RecordWriter.class,
OutputCommitter.class,
StatusReporter.class,
InputSplit.class);
Method get_counter;
try
{
get_counter = Class.forName(PACKAGE + ".TaskAttemptContext").getMethod("getCounter", String.class,
String.class);
}
catch (Exception e)
{
get_counter = Class.forName(PACKAGE + ".TaskInputOutputContext").getMethod("getCounter",
String.class, String.class);
}
GET_COUNTER_METHOD = get_counter;
}
else
{
MAP_CONTEXT_CONSTRUCTOR =
mapContextCls.getConstructor(Configuration.class,
TaskAttemptID.class,
RecordReader.class,
RecordWriter.class,
OutputCommitter.class,
StatusReporter.class,
InputSplit.class);
GET_COUNTER_METHOD = Class.forName(PACKAGE+".TaskInputOutputContext")
.getMethod("getCounter", String.class, String.class);
}
MAP_CONTEXT_CONSTRUCTOR.setAccessible(true);
READER_FIELD = mapContextCls.getDeclaredField("reader");
READER_FIELD.setAccessible(true);
WRITER_FIELD = taskIOContextCls.getDeclaredField("output");
WRITER_FIELD.setAccessible(true);
GET_CONFIGURATION_METHOD = Class.forName(PACKAGE+".JobContext")
.getMethod("getConfiguration");
SET_STATUS_METHOD = Class.forName(PACKAGE+".TaskAttemptContext")
.getMethod("setStatus", String.class);
GET_TASK_ATTEMPT_ID = Class.forName(PACKAGE+".TaskAttemptContext")
.getMethod("getTaskAttemptID");
INCREMENT_COUNTER_METHOD = Class.forName(PACKAGE+".Counter")
.getMethod("increment", Long.TYPE);
PROGRESS_METHOD = Class.forName(PACKAGE+".TaskAttemptContext")
.getMethod("progress");
}
catch (SecurityException e)
{
throw new IllegalArgumentException("Can't run constructor ", e);
}
catch (NoSuchMethodException e)
{
throw new IllegalArgumentException("Can't find constructor ", e);
}
catch (NoSuchFieldException e)
{
throw new IllegalArgumentException("Can't find field ", e);
}
catch (ClassNotFoundException e)
{
throw new IllegalArgumentException("Can't find class", e);
}
}
/**
* True if runtime Hadoop version is 2.x, false otherwise.
*/
public static boolean isVersion2x()
{
return useV21;
}
private static Object newInstance(Constructor constructor, Object...args)
{
try
{
return constructor.newInstance(args);
}
catch (InstantiationException e)
{
throw new IllegalArgumentException("Can't instantiate " + constructor, e);
}
catch (IllegalAccessException e)
{
throw new IllegalArgumentException("Can't instantiate " + constructor, e);
}
catch (InvocationTargetException e)
{
throw new IllegalArgumentException("Can't instantiate " + constructor, e);
}
}
/**
* Creates JobContext from a JobConf and jobId using the correct constructor
* for based on Hadoop version. jobId could be null.
*/
public static JobContext newJobContext(Configuration conf, JobID jobId) {
return (JobContext) newInstance(JOB_CONTEXT_CONSTRUCTOR, conf, jobId);
}
/**
* Creates TaskAttempContext from a JobConf and jobId using the correct
* constructor for based on Hadoop version.
*/
public static TaskAttemptContext newTaskAttemptContext(
Configuration conf, TaskAttemptID taskAttemptId) {
return (TaskAttemptContext)
newInstance(TASK_CONTEXT_CONSTRUCTOR, conf, taskAttemptId);
}
/**
* Instantiates MapContext under Hadoop 1 and MapContextImpl under Hadoop 2.
*/
public static MapContext newMapContext(Configuration conf,
TaskAttemptID taskAttemptID,
RecordReader recordReader,
RecordWriter recordWriter,
OutputCommitter outputCommitter,
StatusReporter statusReporter,
InputSplit inputSplit) {
return (MapContext) newInstance(MAP_CONTEXT_CONSTRUCTOR,
conf, taskAttemptID, recordReader, recordWriter, outputCommitter,
statusReporter, inputSplit);
}
/**
* @return with Hadoop 2 : new GenericCounter(args),
* with Hadoop 1 : new Counter(args)
*/
public static Counter newGenericCounter(String name, String displayName, long value)
{
try
{
return (Counter)
GENERIC_COUNTER_CONSTRUCTOR.newInstance(name, displayName, value);
}
catch (InstantiationException | IllegalAccessException | InvocationTargetException e)
{
throw new IllegalArgumentException("Can't instantiate Counter", e);
}
}
/**
* Invokes a method and rethrows any exception as runtime excetpions.
*/
private static Object invoke(Method method, Object obj, Object... args)
{
try
{
return method.invoke(obj, args);
}
catch (IllegalAccessException | InvocationTargetException e)
{
throw new IllegalArgumentException("Can't invoke method " + method.getName(), e);
}
}
/**
* Invoke getConfiguration() on JobContext. Works with both
* Hadoop 1 and 2.
*/
public static Configuration getConfiguration(JobContext context)
{
return (Configuration) invoke(GET_CONFIGURATION_METHOD, context);
}
/**
* Invoke setStatus() on TaskAttemptContext. Works with both
* Hadoop 1 and 2.
*/
public static void setStatus(TaskAttemptContext context, String status)
{
invoke(SET_STATUS_METHOD, context, status);
}
/**
* returns TaskAttemptContext.getTaskAttemptID(). Works with both
* Hadoop 1 and 2.
*/
public static TaskAttemptID getTaskAttemptID(TaskAttemptContext taskContext)
{
return (TaskAttemptID) invoke(GET_TASK_ATTEMPT_ID, taskContext);
}
/**
* Invoke getCounter() on TaskInputOutputContext. Works with both
* Hadoop 1 and 2.
*/
public static Counter getCounter(TaskInputOutputContext context,
String groupName, String counterName)
{
return (Counter) invoke(GET_COUNTER_METHOD, context, groupName, counterName);
}
/**
* Invoke TaskAttemptContext.progress(). Works with both
* Hadoop 1 and 2.
*/
public static void progress(TaskAttemptContext context)
{
invoke(PROGRESS_METHOD, context);
}
/**
* Increment the counter. Works with both Hadoop 1 and 2
*/
public static void incrementCounter(Counter counter, long increment)
{
// incrementing a count might be called often. Might be affected by
// cost of invoke(). might be good candidate to handle in a shim.
// (TODO Raghu) figure out how achieve such a build with maven
invoke(INCREMENT_COUNTER_METHOD, counter, increment);
}
}