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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.flink.python;

import org.apache.flink.annotation.Internal;

/**
 * The base interface of runner which is responsible for the execution of Python functions.
 *
 * @param  Type of the input elements.
 */
@Internal
public interface PythonFunctionRunner {

	/**
	 * Prepares the Python function runner, such as preparing the Python execution environment, etc.
	 */
	void open() throws Exception;

	/**
	 * Tear-down the Python function runner.
	 */
	void close() throws Exception;

	/**
	 * Prepares to process the next bundle of elements.
	 */
	void startBundle() throws Exception;

	/**
	 * Forces to finish the processing of the current bundle of elements. It will flush
	 * the data cached in the data buffer for processing and retrieves the state mutations (if exists)
	 * made by the Python function. The call blocks until all of the outputs produced by this
	 * bundle have been received.
	 */
	void finishBundle() throws Exception;

	/**
	 * Executes the Python function with the input element. It's not required to execute
	 * the Python function immediately. The runner may choose to buffer the input element and
	 * execute them in batch for better performance.
	 */
	void processElement(IN element) throws Exception;
}