/*
* 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.operators;
import org.apache.flink.api.common.functions.Function;
/**
* The interface to be implemented by all drivers that run alone (or as the primary driver) in a task.
* A driver implements the actual code to perform a batch operation, like <i>map()</i>,
* <i>reduce()</i>, <i>join()</i>, or <i>coGroup()</i>.
*
* @see TaskContext
*
* @param <S> The type of stub driven by this driver.
* @param <OT> The data type of the records produced by this driver.
*/
public interface Driver<S extends Function, OT> {
void setup(TaskContext<S, OT> context);
/**
* Gets the number of inputs that the task has.
*
* @return The number of inputs.
*/
int getNumberOfInputs();
/**
* Gets the number of comparators required for this driver.
*
* @return The number of comparators required for this driver.
*/
int getNumberOfDriverComparators();
/**
* Gets the class of the stub type that is run by this task. For example, a <tt>MapTask</tt> should return
* <code>MapFunction.class</code>.
*
* @return The class of the stub type run by the task.
*/
Class<S> getStubType();
/**
* This method is called before the user code is opened. An exception thrown by this method
* signals failure of the task.
*
* @throws Exception Exceptions may be forwarded and signal task failure.
*/
void prepare() throws Exception;
/**
* The main operation method of the task. It should call the user code with the data subsets until
* the input is depleted.
*
* @throws Exception Any exception thrown by this method signals task failure. Because exceptions in the user
* code typically signal situations where this instance in unable to proceed, exceptions
* from the user code should be forwarded.
*/
void run() throws Exception;
/**
* This method is invoked in any case (clean termination and exception) at the end of the tasks operation.
*
* @throws Exception Exceptions may be forwarded.
*/
void cleanup() throws Exception;
/**
* This method is invoked when the driver must aborted in mid processing. It is invoked asynchronously by a different thread.
*
* @throws Exception Exceptions may be forwarded.
*/
void cancel() throws Exception;
}