com.hazelcast.mapreduce.TopologyChangedStrategy 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 enum class is used to define how a map reduce job behaves
* if the job owner recognizes a topology changed event.
* When members are leaving the cluster, it might lose
* processed data chunks that were already send to the reducers
* on the leaving node.
* Also, on any topology change, there is a redistribution
* of the member assigned partitions, which means that a map job might
* have a problem finishing its currently processed partition.
* The default behavior is to immediately cancel the running task and
* throw an {@link TopologyChangedException}, but it is possible
* to submit the same job configuration again if
* {@link com.hazelcast.mapreduce.JobTracker#getTrackableJob(String)}
* returns null for the requested job id.
*
* @since 3.2
*/
@Beta
public enum TopologyChangedStrategy {
/**
* Default behavior. The currently running job is cancelled
* immediately on recognizing the topology changed. An
* {@link TopologyChangedException} is thrown on the job owning
* node.
*/
CANCEL_RUNNING_OPERATION,
/**
* Attention: This strategy is currently not available but
* reserved for later usage!
* Some or all processed data and intermediate results are
* discarded and the job is automatically restarted.
* Depending on the implementation, the job might start from
* an earlier reached safepoint and is not restarted at the
* beginning.
*/
DISCARD_AND_RESTART,
/**
* Attention: This strategy is currently not available but
* reserved for later usage!
* Currently running processes define a safepoint, migrate
* gracefully and continue their work on new partition owners.
* If a member lefts the cluster intermediately reduced data are lost!
*/
MIGRATE_AND_CONTINUE,
}