org.apache.kafka.streams.processor.api.Processor Maven / Gradle / Ivy
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* 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
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*/
package org.apache.kafka.streams.processor.api;
import org.apache.kafka.streams.processor.PunctuationType;
import org.apache.kafka.streams.processor.Punctuator;
import org.apache.kafka.streams.processor.StateStore;
import java.time.Duration;
/**
* A processor of key-value pair records.
*
* @param the type of input keys
* @param the type of input values
* @param the type of output keys
* @param the type of output values
*/
public interface Processor {
/**
* Initialize this processor with the given context. The framework ensures this is called once per processor when the topology
* that contains it is initialized. When the framework is done with the processor, {@link #close()} will be called on it; the
* framework may later re-use the processor by calling {@code #init()} again.
*
* The provided {@link ProcessorContext context} can be used to access topology and record meta data, to
* {@link ProcessorContext#schedule(Duration, PunctuationType, Punctuator) schedule} a method to be
* {@link Punctuator#punctuate(long) called periodically} and to access attached {@link StateStore}s.
*
* @param context the context; may not be null
*/
default void init(final ProcessorContext context) {}
/**
* Process the record. Note that record metadata is undefined in cases such as a forward call from a punctuator.
*
* @param record the record to process
*/
void process(Record record);
/**
* Close this processor and clean up any resources. Be aware that {@code #close()} is called after an internal cleanup.
* Thus, it is not possible to write anything to Kafka as underlying clients are already closed. The framework may
* later re-use this processor by calling {@code #init()} on it again.
*
* Note: Do not close any streams managed resources, like {@link StateStore}s here, as they are managed by the library.
*/
default void close() {}
}