com.hazelcast.mapreduce.Job Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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.hazelcast.mapreduce;
import com.hazelcast.spi.annotation.Beta;
/**
*
* This interface describes a mapreduce Job that is build by {@link JobTracker#newJob(KeyValueSource)}.
* It is used to execute mappings and calculations on the different cluster nodes and reduce or collate these mapped
* values to results.
*
*
* Implementations returned by the JobTracker are fully threadsafe and can be used concurrently and multiple
* times once the configuration is finished.
*
*
* Caution: The generic types of Jobs change depending on the used methods, which can make it necessary to use
* different assignment variables when used over multiple source lines.
*
*
* An example on how to use it:
*
* HazelcastInstance hz = getHazelcastInstance();
* IMap<Integer, Integer> map = (...) hz.getMap( "default" );
* JobTracker tracker = hz.getJobTracker( "default" );
* Job<Integer, Integer> job = tracker.newJob( KeyValueSource.fromMap( map ) );
* ICompletableFuture<Map<String, Integer>> future = job
* .mapper( buildMapper() ).reducer( buildReducer() ).submit();
* Map<String, Integer> results = future.get();
*
*
*
* @param type of key used as input key type
* @param type of value used as input value type
* @since 3.2
*/
@Beta
public interface Job {
/**
* Defines keys to execute the mapper and a possibly defined reducer against. If keys are known before submitting
* the task, setting them can improve execution speed.
*
* @param keys keys to be executed against
* @return instance of this Job with generics changed on usage
*/
Job onKeys(Iterable keys);
/**
* Defines keys to execute the mapper and a possibly defined reducer against. If keys are known before submitting
* the task, setting them can improve execution speed.
*
* @param keys keys to be executed against
* @return instance of this Job with generics changed on usage
*/
Job onKeys(KeyIn... keys);
/**
* Defines the number of elements per chunk. Whenever the chunk size is reached and a
* {@link com.hazelcast.mapreduce.ReducerFactory} is defined, the chunk will be sent to the nodes that
* is responsible for the emitted keys.
* Please note, that chunks are deactivated when no ReducerFactory is defined
*
* @param chunkSize the number of elements per chunk
* @return instance of this Job with generics changed on usage
*/
Job chunkSize(int chunkSize);
/**
* Defines the strategy to handle topology changes while executing the map reduce job. For further
* information see {@link com.hazelcast.mapreduce.TopologyChangedStrategy}.
*
* @param topologyChangedStrategy strategy to handle topology changes while executing the map reduce job
* @return instance of this Job with generics changed on usage
*/
Job topologyChangedStrategy(TopologyChangedStrategy topologyChangedStrategy);
/**
* Defines the {@link KeyPredicate} implementation to preselect keys the MapReduce task will be executed on.
* Preselecting keys can speed up the job massively.
* This method can be used in conjunction with {@link #onKeys(Iterable)} or {@link #onKeys(Object...)} to define a
* range of known and evaluated keys.
*
* @param predicate predicate implementation to be used to evaluate keys
* @return instance of this Job with generics changed on usage
*/
Job keyPredicate(KeyPredicate predicate);
/**
* Defines the mapper for this task. This method is not idempotent and can be callable only one time. Further
* calls result in an {@link IllegalStateException} to be thrown telling you to not change the internal state.
*
* @param mapper tasks mapper
* @param type of the emitted key
* @param type of the emitted value
* @return instance of this Job with generics changed on usage
*/
MappingJob mapper(Mapper mapper);
}