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Apache Hadoop Common

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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.io.retry;

import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * Used to mark certain methods of an interface with at-most-once semantics.
 * 
 * Server must guarantee that methods are executed at most once, by keeping
 * a retry cache. The previous response must be returned when duplicate 
 * requests are received. Because of these guarantee, a client can retry
 * this request on failover and other network failure conditions.
 */
@Inherited
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@InterfaceStability.Evolving
public @interface AtMostOnce {

}