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Posted to github@beam.apache.org by GitBox <gi...@apache.org> on 2020/09/02 00:46:38 UTC
[GitHub] [beam] nehsyc commented on a change in pull request #12726: [BEAM-10475] Add max buffering duration to GroupIntoBatches (Java)
nehsyc commented on a change in pull request #12726:
URL: https://github.com/apache/beam/pull/12726#discussion_r481510949
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File path: sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/GroupIntoBatches.java
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@@ -150,70 +184,95 @@ public long apply(long left, long right) {
});
this.keySpec = StateSpecs.value(inputKeyCoder);
- // prefetch every 20% of batchSize elements. Do not prefetch if batchSize is too little
+ // Prefetch every 20% of batchSize elements. Do not prefetch if batchSize is too little
this.prefetchFrequency = ((batchSize / 5) <= 1) ? Long.MAX_VALUE : (batchSize / 5);
}
@ProcessElement
public void processElement(
- @TimerId(END_OF_WINDOW_ID) Timer timer,
+ @TimerId(END_OF_WINDOW_ID) Timer windowTimer,
+ @TimerId(END_OF_BUFFERING_ID) Timer bufferingTimer,
@StateId(BATCH_ID) BagState<InputT> batch,
@StateId(NUM_ELEMENTS_IN_BATCH_ID) CombiningState<Long, long[], Long> numElementsInBatch,
@StateId(KEY_ID) ValueState<K> key,
@Element KV<K, InputT> element,
BoundedWindow window,
OutputReceiver<KV<K, Iterable<InputT>>> receiver) {
- Instant windowExpires = window.maxTimestamp().plus(allowedLateness);
-
- LOG.debug(
- "*** SET TIMER *** to point in time {} for window {}",
- windowExpires.toString(),
- window.toString());
- timer.set(windowExpires);
+ Instant windowEnds = window.maxTimestamp().plus(allowedLateness);
+ LOG.debug("*** SET TIMER *** to point in time {} for window {}", windowEnds, window);
+ windowTimer.set(windowEnds);
key.write(element.getKey());
+ LOG.debug("*** BATCH *** Add element for window {} ", window);
batch.add(element.getValue());
- LOG.debug("*** BATCH *** Add element for window {} ", window.toString());
- // blind add is supported with combiningState
+ // Blind add is supported with combiningState
numElementsInBatch.add(1L);
+
Long num = numElementsInBatch.read();
+ if (num == 1 && maxBufferingDuration.isLongerThan(Duration.ZERO)) {
+ // This is the first element in batch. Start counting buffering time if a limit was set.
+ bufferingTimer.offset(maxBufferingDuration).setRelative();
+ }
if (num % prefetchFrequency == 0) {
- // prefetch data and modify batch state (readLater() modifies this)
+ // Prefetch data and modify batch state (readLater() modifies this)
batch.readLater();
}
if (num >= batchSize) {
LOG.debug("*** END OF BATCH *** for window {}", window.toString());
- flushBatch(receiver, key, batch, numElementsInBatch);
+ flushBatch(receiver, key, batch, numElementsInBatch, bufferingTimer);
}
}
+ @OnTimer(END_OF_BUFFERING_ID)
+ public void onBufferingTimer(
+ OutputReceiver<KV<K, Iterable<InputT>>> receiver,
+ @Timestamp Instant timestamp,
+ @StateId(KEY_ID) ValueState<K> key,
+ @StateId(BATCH_ID) BagState<InputT> batch,
+ @StateId(NUM_ELEMENTS_IN_BATCH_ID) CombiningState<Long, long[], Long> numElementsInBatch,
+ @TimerId(END_OF_BUFFERING_ID) Timer bufferingTimer) {
+ LOG.debug(
+ "*** END OF BUFFERING *** for timer timestamp {} with buffering duration {}",
+ timestamp,
+ maxBufferingDuration);
+ flushBatch(receiver, key, batch, numElementsInBatch, bufferingTimer);
+ }
+
@OnTimer(END_OF_WINDOW_ID)
- public void onTimerCallback(
+ public void onWindowTimer(
OutputReceiver<KV<K, Iterable<InputT>>> receiver,
@Timestamp Instant timestamp,
@StateId(KEY_ID) ValueState<K> key,
@StateId(BATCH_ID) BagState<InputT> batch,
@StateId(NUM_ELEMENTS_IN_BATCH_ID) CombiningState<Long, long[], Long> numElementsInBatch,
+ @TimerId(END_OF_BUFFERING_ID) Timer bufferingTimer,
BoundedWindow window) {
LOG.debug(
"*** END OF WINDOW *** for timer timestamp {} in windows {}",
timestamp,
window.toString());
- flushBatch(receiver, key, batch, numElementsInBatch);
+ flushBatch(receiver, key, batch, numElementsInBatch, bufferingTimer);
}
private void flushBatch(
OutputReceiver<KV<K, Iterable<InputT>>> receiver,
ValueState<K> key,
BagState<InputT> batch,
- CombiningState<Long, long[], Long> numElementsInBatch) {
+ CombiningState<Long, long[], Long> numElementsInBatch,
+ Timer bufferingTimer) {
Iterable<InputT> values = batch.read();
- // when the timer fires, batch state might be empty
+ // When the timer fires, batch state might be empty
if (!Iterables.isEmpty(values)) {
receiver.output(KV.of(key.read(), values));
}
batch.clear();
LOG.debug("*** BATCH *** clear");
numElementsInBatch.clear();
+ // We might reach here due to batch size being reached, window expiration or buffering time
+ // limit being reached. Reset the buffering timer anyway since the state is empty now. It'll
+ // be reset again if a new element arrives before the expiration time set here.
+ if (maxBufferingDuration.isLongerThan(Duration.ZERO)) {
+ bufferingTimer.offset(maxBufferingDuration).setRelative();
Review comment:
By clearing the timer, do you mean to extend the deadline like what I am doing now or set it to something else?
I feel it's a little bit cleaner to put it in FlushBatch since we always want to reset the buffering time when a batch is flushed, whatever the reason is. wdyt?
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