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/*
 * Copyright 2012, 2020 International Business Machines Corp.
 *
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership. 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.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

package jakarta.batch.api.partition;

/**
 * PartitionReducer provides unit of work demarcation across
 * partitions. It is not a JTA transaction;  no resources are
 * enlisted.  Rather, it provides transactional flow semantics
 * to facilitate finalizing merge or compensation logic.
 *
 */
public interface PartitionReducer {

	/**
	 * An enum used in {@link PartitionReducer#afterPartitionedStepCompletion(PartitionStatus)}.
	 */
	public enum PartitionStatus {COMMIT, ROLLBACK}

	/**
	 * The beginPartitionedStep method receives
	 * control at the start of partition processing.
	 * It receives control before the PartitionMapper
	 * is invoked and before any partitions are started.
	 * @throws Exception is thrown if an error occurs.
	 */
	public void beginPartitionedStep() throws Exception;
	/**
	 * The beforePartitionedStepCompletion method
	 * receives control at the end of partitioned
	 * step processing. It receives control after all
	 * partitions have completed.  It does not receive
	 * control if the PartitionReducer is rolling back.
	 * @throws Exception is thrown if an error occurs.
	 */
	public void beforePartitionedStepCompletion() throws Exception;
	/**
	 * 
	 * The rollbackPartitionedStep method receives
	 * control if the runtime is rolling back a partitioned
	 * step. Any partition threads still running are
	 * allowed to complete before this method is invoked. This method
	 * receives control if any of the following conditions
	 * are true:
	 * 
	 * 
	 * One or more partitions end with a Batch Status of
	 * STOPPED or FAILED.
	 * Any of the following partitioned step callbacks
	 * throw an exception:
	 * 
PartitionMapper
	 * 
PartitionReducer
	 * 
PartitionCollector
	 * 
PartitionAnalyzer
	 * A job with partitioned steps is restarted.
	 * 
	 * @throws Exception is thrown if an error occurs.
	 */
	public void rollbackPartitionedStep() throws Exception;
	/**
	 * The afterPartitionedStepCompletion method receives control
	 * at the end of a partition processing.  It receives a status
	 * value that identifies the outcome of the partition processing.
	 * The status string value is either "COMMIT" or "ROLLBACK".
	 * @param status specifies the outcome of the partitioned step. Values
	 * are "COMMIT" or "ROLLBACK".
	 * @throws Exception is thrown if an error occurs.
	 */
	public void afterPartitionedStepCompletion(PartitionStatus status) throws Exception;
}