junaiddshaukat commented on code in PR #39494: URL: https://github.com/apache/beam/pull/39494#discussion_r3656509877
########## runners/kafka-streams/src/main/java/org/apache/beam/runners/kafka/streams/translation/KafkaStreamsTimerInternals.java: ########## @@ -0,0 +1,180 @@ +/* + * 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.beam.runners.kafka.streams.translation; + +import java.io.ByteArrayOutputStream; +import java.nio.charset.StandardCharsets; +import org.apache.beam.runners.core.StateNamespace; +import org.apache.beam.runners.core.TimerInternals; +import org.apache.beam.sdk.coders.Coder; +import org.apache.beam.sdk.coders.CoderException; +import org.apache.beam.sdk.state.TimeDomain; +import org.apache.beam.sdk.transforms.windowing.BoundedWindow; +import org.apache.beam.sdk.util.CoderUtils; +import org.apache.kafka.streams.state.KeyValueStore; +import org.checkerframework.checker.nullness.qual.Nullable; +import org.joda.time.Instant; + +/** + * A {@link TimerInternals} for one key, backed by a shared Kafka Streams timer {@link + * KeyValueStore} for a GroupByKey. + * + * <p>Kafka Streams has no per-key timer service, so timers are persisted like any other state. A + * timer is stored under a key built from its identity — {@code key | domain | timerFamily | timerId + * | namespace} — so setting a timer with the same identity overwrites the previous one and deleting + * it removes exactly that entry, matching {@link TimerInternals}' contract. The value is the {@link + * TimerData} encoded with {@link TimerInternals.TimerDataCoderV2}, which carries the fire time. + * + * <p>Firing is driven by {@link WindowedGroupByKeyProcessor}: on a watermark advance it scans the + * store for event-time timers whose fire time has passed and replays them through {@link + * org.apache.beam.runners.core.ReduceFnRunner#onTimers}. Scanning the whole store per advance is + * O(timers); acceptable for this first windowing support and replaceable with a fire-time-ordered + * index later, the same way the initial GroupByKey buffered eagerly. + * + * <p>This instance reports the current input-watermark and processing times it was constructed with + * (the caller advances them as reports arrive); it never fires timers itself. + */ +class KafkaStreamsTimerInternals implements TimerInternals { + + private final byte[] encodedKey; + private final KeyValueStore<byte[], byte[]> timerStore; + private final TimerInternals.TimerDataCoderV2 timerCoder; + private final Instant inputWatermarkTime; + private final Instant processingTime; + + KafkaStreamsTimerInternals( + byte[] encodedKey, + KeyValueStore<byte[], byte[]> timerStore, + Coder<? extends BoundedWindow> windowCoder, + Instant inputWatermarkTime, + Instant processingTime) { + this.encodedKey = encodedKey; + this.timerStore = timerStore; + this.timerCoder = TimerInternals.TimerDataCoderV2.of(windowCoder); + this.inputWatermarkTime = inputWatermarkTime; + this.processingTime = processingTime; + } + + @Override + public void setTimer( + StateNamespace namespace, + String timerId, + String timerFamilyId, + Instant target, + Instant outputTimestamp, + TimeDomain timeDomain) { + setTimer(TimerData.of(timerId, timerFamilyId, namespace, target, outputTimestamp, timeDomain)); + } + + @Override + public void setTimer(TimerData timerData) { + timerStore.put(timerStoreKey(encodedKey, timerData), encodeTimer(timerData)); + } + + @Override + public void deleteTimer( + StateNamespace namespace, String timerId, String timerFamilyId, TimeDomain timeDomain) { + timerStore.delete(timerStoreKey(encodedKey, timerId, timerFamilyId, timeDomain, namespace)); + } + + @Override + public void deleteTimer(StateNamespace namespace, String timerId, String timerFamilyId) { + throw new UnsupportedOperationException( + "Deleting a timer without a time domain is not supported; the domain is part of a timer's" + + " store identity."); + } + + @Override + public void deleteTimer(TimerData timerKey) { + timerStore.delete(timerStoreKey(encodedKey, timerKey)); + } + + @Override + public Instant currentProcessingTime() { + return processingTime; + } + + @Override + public @Nullable Instant currentSynchronizedProcessingTime() { + return null; + } + + @Override + public Instant currentInputWatermarkTime() { + return inputWatermarkTime; + } + + @Override + public @Nullable Instant currentOutputWatermarkTime() { + return null; + } + + private byte[] encodeTimer(TimerData timerData) { + try { + return CoderUtils.encodeToByteArray(timerCoder, timerData); + } catch (CoderException e) { + throw new RuntimeException("Failed to encode timer " + timerData, e); + } + } + + /** The store key for a timer's identity. Package-visible so the processor can build/scan it. */ + static byte[] timerStoreKey(byte[] encodedKey, TimerData timerData) { + return timerStoreKey( + encodedKey, + timerData.getTimerId(), + timerData.getTimerFamilyId(), + timerData.getDomain(), + timerData.getNamespace()); + } + + static byte[] timerStoreKey( + byte[] encodedKey, + String timerId, + String timerFamilyId, + TimeDomain domain, + StateNamespace namespace) { + ByteArrayOutputStream out = new ByteArrayOutputStream(); + writeSegment(out, encodedKey); Review Comment: Thanks, kept it exactly for that reason. The scan reads the encoded key back out of the key, so the prefixes have to stay here. I wrote that down in StoreKeys so it doesn't get "optimized" away later. -- 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]
