io.debezium.function.BufferedBlockingConsumer Maven / Gradle / Ivy
/*
* Copyright Debezium Authors.
*
* Licensed under the Apache Software License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
*/
package io.debezium.function;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Function;
/**
* A {@link BlockingConsumer} that retains a maximum number of values in a buffer before sending them to
* a delegate consumer.
*
* This maintains the same order of the values.
*
* @param the type of the input to the operation
* @author Randall Hauch
*/
public interface BufferedBlockingConsumer extends BlockingConsumer {
/**
* Flush all of the buffered values to the delegate by first running each buffered value through the given function
* to generate a new value to be flushed to the delegate consumer.
*
* {@link #accept(Object)} may not be called after this method has been called.
*
* @param function the function to apply to the values that are flushed
* @throws InterruptedException if the thread is interrupted while this consumer is blocked
*/
public void close(Function function) throws InterruptedException;
/**
* Get a {@link BufferedBlockingConsumer} that buffers just the last value seen by the consumer.
* When another value is then added to the consumer, this buffered consumer will push the prior value into the delegate
* and buffer the latest.
*
* The resulting consumer is threadsafe.
*
* @param delegate the delegate to which values should be flushed; may not be null
* @return the blocking consumer that buffers a single value at a time; never null
*/
public static BufferedBlockingConsumer bufferLast(BlockingConsumer delegate) {
return new BufferedBlockingConsumer() {
private final AtomicReference last = new AtomicReference<>();
@Override
public void accept(T t) throws InterruptedException {
T previous = last.getAndSet(t);
if (previous != null) {
delegate.accept(previous);
}
}
@Override
public synchronized void close(Function function) throws InterruptedException {
T previous = last.get();
if (previous != null) {
try {
delegate.accept(function.apply(previous));
}
finally {
last.set(null);
}
}
}
};
}
}