/*
* 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.api.common.functions;
import org.apache.flink.annotation.PublicEvolving;
/**
* Must be implemented by stoppable functions, eg, source functions of streaming jobs. The method {@link #stop()} will
* be called when the job received the STOP signal. On this signal, the source function must stop emitting new data and
* terminate gracefully.
*/
@PublicEvolving
public interface StoppableFunction {
/**
* Stops the source. In contrast to {@code cancel()} this is a request to the source function to shut down
* gracefully. Pending data can still be emitted and it is not required to stop immediately -- however, in the near
* future. The job will keep running until all emitted data is processed completely.
* <p>
* Most streaming sources will have a while loop inside the {@code run()} method. You need to ensure that the source
* will break out of this loop. This can be achieved by having a volatile field "isRunning" that is checked in the
* loop and that is set to false in this method.
* <p>
* <strong>The call to {@code stop()} should not block and not throw any exception.</strong>
*/
void stop();
}