org.apache.flink.streaming.api.operators.InputSelectable Maven / Gradle / Ivy
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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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.streaming.api.operators;
import org.apache.flink.annotation.PublicEvolving;
/**
* Interface for stream operators that can select the input to get {@link
* org.apache.flink.streaming.runtime.streamrecord.StreamRecord}.
*
* IMPORTANT: This interface is a loose contract. The runtime may read multiple records
* continuously before calling {@code nextSelection()} again to determine whether to change the
* input to be read. That is, it is not guaranteed that {@code nextSelection()} will be called
* immediately after the operator has processed a record and the reading input will be changed
* according to {@link InputSelection} returned. This means that the operator may receive some data
* that it does not currently want to process. Therefore, if an operator needs a strict convention,
* it must cache the unexpected data itself and handle them correctly.
*
*
This interface also makes the following conventions: 1.The runtime must call {@code
* nextSelection()} to determine the input to read the first record. 2.When the input being read
* reaches the end, the runtime must call {@code nextSelection()} to determine the next input to be
* read.
*/
@PublicEvolving
public interface InputSelectable {
/**
* Returns the next {@link InputSelection} that wants to get the record. This method is
* guaranteed to not be called concurrently with other methods of the operator.
*/
InputSelection nextSelection();
}