org.apache.flink.runtime.io.AsyncDataInput 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.Optional;
import java.util.concurrent.CompletableFuture;
/**
* Interface defining couple of essential methods for asynchronous and non blocking data polling.
*
* For the most efficient usage, user of this class is supposed to call {@link #pollNext()}
* until it returns that no more elements are available. If that happens, he should check if
* input {@link #isFinished()}. If not, he should wait for {@link #isAvailable()}
* {@link CompletableFuture} to be completed. For example:
*
*
* {@code
* AsyncDataInput input = ...;
* while (!input.isFinished()) {
* Optional next;
*
* while (true) {
* next = input.pollNext();
* if (!next.isPresent()) {
* break;
* }
* // do something with next
* }
*
* input.isAvailable().get();
* }
* }
*
*/
@Internal
public interface AsyncDataInput extends AvailabilityListener {
/**
* Poll the next element. This method should be non blocking.
*
* @return {@code Optional.empty()} will be returned if there is no data to return or
* if {@link #isFinished()} returns true. Otherwise {@code Optional.of(element)}.
*/
Optional pollNext() throws Exception;
}