kafka KTableReduce 源码
kafka KTableReduce 代码
文件路径:/streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableReduce.java
/*
* 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.kafka.streams.kstream.internals;
import org.apache.kafka.streams.errors.StreamsException;
import org.apache.kafka.streams.kstream.Reducer;
import org.apache.kafka.streams.processor.api.Processor;
import org.apache.kafka.streams.processor.api.ProcessorContext;
import org.apache.kafka.streams.processor.api.Record;
import org.apache.kafka.streams.state.TimestampedKeyValueStore;
import org.apache.kafka.streams.state.ValueAndTimestamp;
import static org.apache.kafka.streams.state.ValueAndTimestamp.getValueOrNull;
public class KTableReduce<K, V> implements KTableProcessorSupplier<K, V, K, V> {
private final String storeName;
private final Reducer<V> addReducer;
private final Reducer<V> removeReducer;
private boolean sendOldValues = false;
KTableReduce(final String storeName, final Reducer<V> addReducer, final Reducer<V> removeReducer) {
this.storeName = storeName;
this.addReducer = addReducer;
this.removeReducer = removeReducer;
}
@Override
public boolean enableSendingOldValues(final boolean forceMaterialization) {
// Reduce is always materialized:
sendOldValues = true;
return true;
}
@Override
public Processor<K, Change<V>, K, Change<V>> get() {
return new KTableReduceProcessor();
}
private class KTableReduceProcessor implements Processor<K, Change<V>, K, Change<V>> {
private TimestampedKeyValueStore<K, V> store;
private TimestampedTupleForwarder<K, V> tupleForwarder;
@SuppressWarnings("unchecked")
@Override
public void init(final ProcessorContext<K, Change<V>> context) {
store = (TimestampedKeyValueStore<K, V>) context.getStateStore(storeName);
tupleForwarder = new TimestampedTupleForwarder<>(
store,
context,
new TimestampedCacheFlushListener<>(context),
sendOldValues);
}
/**
* @throws StreamsException if key is null
*/
@Override
public void process(final Record<K, Change<V>> record) {
// the keys should never be null
if (record.key() == null) {
throw new StreamsException("Record key for KTable reduce operator with state " + storeName + " should not be null.");
}
final ValueAndTimestamp<V> oldAggAndTimestamp = store.get(record.key());
final V oldAgg = getValueOrNull(oldAggAndTimestamp);
final V intermediateAgg;
long newTimestamp;
// first try to remove the old value
if (record.value().oldValue != null && oldAgg != null) {
intermediateAgg = removeReducer.apply(oldAgg, record.value().oldValue);
newTimestamp = Math.max(record.timestamp(), oldAggAndTimestamp.timestamp());
} else {
intermediateAgg = oldAgg;
newTimestamp = record.timestamp();
}
// then try to add the new value
final V newAgg;
if (record.value().newValue != null) {
if (intermediateAgg == null) {
newAgg = record.value().newValue;
} else {
newAgg = addReducer.apply(intermediateAgg, record.value().newValue);
newTimestamp = Math.max(record.timestamp(), oldAggAndTimestamp.timestamp());
}
} else {
newAgg = intermediateAgg;
}
// update the store with the new value
store.put(record.key(), ValueAndTimestamp.make(newAgg, newTimestamp));
tupleForwarder.maybeForward(
record.withValue(new Change<>(newAgg, sendOldValues ? oldAgg : null))
.withTimestamp(newTimestamp));
}
}
@Override
public KTableValueGetterSupplier<K, V> view() {
return new KTableMaterializedValueGetterSupplier<>(storeName);
}
}
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