Jess668 commented on code in PR #22975: URL: https://github.com/apache/kafka/pull/22975#discussion_r3731274701
########## streams/src/main/java/org/apache/kafka/streams/state/internals/AbstractMeteredIterator.java: ########## @@ -0,0 +1,100 @@ +/* + * 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.state.internals; + +import org.apache.kafka.common.metrics.Sensor; +import org.apache.kafka.common.utils.Time; +import org.apache.kafka.streams.state.KeyValueIterator; + +import java.util.Set; +import java.util.concurrent.atomic.LongAdder; + +/** + * Shared metering lifecycle for the metered iterators of the {@code Metered*WithHeaders} stores, + * whatever result type they yield: the {@code KeyValueIterator}s returned by the store's own range/ + * fetch/find methods and the {@code ReadOnlyRecordIterator}s that back the headers-aware IQv2 + * range/window/session query types. + * + * <p>Every such iterator opens over a raw {@code KeyValueIterator<RawKey, byte[]>} and needs the + * same bookkeeping: stamp the open time (for the {@code oldest-iterator-open-since-ms} metric), + * register in {@code numOpenIterators}/{@code openIterators}, and on {@link #close()} record the + * operation and iterator-duration sensors and deregister. This base is deliberately result-type + * agnostic -- it implements only {@link MeteredIterator} and does not bind the yielded key/value + * types -- so each subclass declares its own result interface (a {@code KeyValueIterator} or a + * {@code ReadOnlyRecordIterator}) and implements just the parts that genuinely differ: the + * deserializing {@code next()} (and, for the {@code KeyValueIterator}s, a peeking {@code hasNext()} + * and {@code peekNextKey()}). + * + * @param <RawKey> the raw iterator's key type + */ +abstract class AbstractMeteredIterator<RawKey> implements MeteredIterator { + + final KeyValueIterator<RawKey, byte[]> iter; + private final Sensor operationSensor; + private final Sensor iteratorSensor; + private final Time time; + private final LongAdder numOpenIterators; + private final Set<MeteredIterator> openIterators; + private final long startNs; + private final long startTimestampMs; + + AbstractMeteredIterator(final KeyValueIterator<RawKey, byte[]> iter, + final Sensor operationSensor, + final Sensor iteratorSensor, + final Time time, + final LongAdder numOpenIterators, + final Set<MeteredIterator> openIterators) { + this.iter = iter; + this.operationSensor = operationSensor; + this.iteratorSensor = iteratorSensor; + this.time = time; + this.numOpenIterators = numOpenIterators; + this.openIterators = openIterators; + this.startNs = time.nanoseconds(); + this.startTimestampMs = time.milliseconds(); + numOpenIterators.increment(); + openIterators.add(this); + } + + // Final: the constructor's openIterators.add(this) sorts through this via the set's + // startTimestamp comparator, i.e. on a not-yet-fully-constructed object. Keeping it final stops a + // subclass from overriding it with something that reads its own not-yet-assigned state. + @Override + public final long startTimestamp() { + return startTimestampMs; + } + + /** + * Delegates to the raw iterator. Subclasses that buffer a peeked element (the + * {@code KeyValueIterator}s) override this to also account for the buffered element. + */ + public boolean hasNext() { + return iter.hasNext(); + } + + public void close() { + try { + iter.close(); + } finally { + final long duration = time.nanoseconds() - startNs; + operationSensor.record(duration); + iteratorSensor.record(duration); + numOpenIterators.decrement(); + openIterators.remove(this); Review Comment: https://issues.apache.org/jira/browse/KAFKA-20902 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
