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/**
* 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;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.mapred.Counters.Counter;
import org.apache.hadoop.util.Progressable;
/**
* A facility for Map-Reduce applications to report progress and update
* counters, status information etc.
*
* {@link Mapper} and {@link Reducer} can use the Reporter
* provided to report progress or just indicate that they are alive. In
* scenarios where the application takes an insignificant amount of time to
* process individual key/value pairs, this is crucial since the framework
* might assume that the task has timed-out and kill that task.
*
*
Applications can also update {@link Counters} via the provided
* Reporter .
*
* @see Progressable
* @see Counters
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public interface Reporter extends Progressable {
/**
* A constant of Reporter type that does nothing.
*/
public static final Reporter NULL = new Reporter() {
public void setStatus(String s) {
}
public void progress() {
}
public Counter getCounter(Enum name) {
return null;
}
public Counter getCounter(String group, String name) {
return null;
}
public void incrCounter(Enum key, long amount) {
}
public void incrCounter(String group, String counter, long amount) {
}
public InputSplit getInputSplit() throws UnsupportedOperationException {
throw new UnsupportedOperationException("NULL reporter has no input");
}
};
/**
* Set the status description for the task.
*
* @param status brief description of the current status.
*/
public abstract void setStatus(String status);
/**
* Get the {@link Counter} of the given group with the given name.
*
* @param name counter name
* @return the Counter of the given group/name.
*/
public abstract Counter getCounter(Enum name);
/**
* Get the {@link Counter} of the given group with the given name.
*
* @param group counter group
* @param name counter name
* @return the Counter of the given group/name.
*/
public abstract Counter getCounter(String group, String name);
/**
* Increments the counter identified by the key, which can be of
* any {@link Enum} type, by the specified amount.
*
* @param key key to identify the counter to be incremented. The key can be
* be any Enum.
* @param amount A non-negative amount by which the counter is to
* be incremented.
*/
public abstract void incrCounter(Enum key, long amount);
/**
* Increments the counter identified by the group and counter name
* by the specified amount.
*
* @param group name to identify the group of the counter to be incremented.
* @param counter name to identify the counter within the group.
* @param amount A non-negative amount by which the counter is to
* be incremented.
*/
public abstract void incrCounter(String group, String counter, long amount);
/**
* Get the {@link InputSplit} object for a map.
*
* @return the InputSplit that the map is reading from.
* @throws UnsupportedOperationException if called outside a mapper
*/
public abstract InputSplit getInputSplit()
throws UnsupportedOperationException;
}