org.apache.flink.runtime.io.AvailabilityListener Maven / Gradle / Ivy
/*
* 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.flink.runtime.io;
import org.apache.flink.annotation.Internal;
import java.util.concurrent.CompletableFuture;
/**
* Interface defining couple of essential methods for listening on data availability using
* {@link CompletableFuture}. For usage check out for example {@link AsyncDataInput}.
*/
@Internal
public interface AvailabilityListener {
/**
* Constant that allows to avoid volatile checks {@link CompletableFuture#isDone()}. Check
* {@link #isAvailable()} for more explanation.
*/
CompletableFuture AVAILABLE = CompletableFuture.completedFuture(null);
/**
* @return true if is finished and for example end of input was reached, false otherwise.
*/
boolean isFinished();
/**
* Check if this instance is available for further processing.
*
* When hot looping to avoid volatile access in {@link CompletableFuture#isDone()} user of
* this method should do the following check:
*
* {@code
* AvailabilityListener input = ...;
* if (input.isAvailable() == AvailabilityListener.AVAILABLE || input.isAvailable().isDone()) {
* // do something;
* }
* }
*
*
* @return a future that is completed if there are more records available. If there are more
* records available immediately, {@link #AVAILABLE} should be returned. Previously returned
* not completed futures should become completed once there is more input available or if
* the input {@link #isFinished()}.
*/
CompletableFuture isAvailable();
}