guozhangwang commented on a change in pull request #8964:
URL: https://github.com/apache/kafka/pull/8964#discussion_r459853500
##########
File path:
streams/src/main/java/org/apache/kafka/streams/processor/internals/StateManagerUtil.java
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@@ -38,13 +41,39 @@
*/
final class StateManagerUtil {
static final String CHECKPOINT_FILE_NAME = ".checkpoint";
+ static final long OFFSET_DELTA_THRESHOLD_FOR_CHECKPOINT = 10_000L;
private StateManagerUtil() {}
static RecordConverter converterForStore(final StateStore store) {
return isTimestamped(store) ? rawValueToTimestampedValue() :
identity();
}
+ static boolean checkpointNeeded(final boolean enforceCheckpoint,
+ final Map<TopicPartition, Long>
oldOffsetSnapshot,
+ final Map<TopicPartition, Long>
newOffsetSnapshot) {
+ // we should always have the old snapshot post completing the register
state stores;
+ // if it is null it means the registration is not done and hence we
should not overwrite the checkpoint
+ if (oldOffsetSnapshot == null)
+ return false;
+
+ // if the previous snapshot is empty while the current snapshot is not
then we should always checkpoint;
+ // note if the task is stateless or stateful but no stores logged, the
snapshot would also be empty
+ // and hence it's okay to not checkpoint
+ if (oldOffsetSnapshot.isEmpty() && !newOffsetSnapshot.isEmpty())
+ return true;
+
+ // we can checkpoint if the the difference between the current and the
previous snapshot is large enough
+ long totalOffsetDelta = 0L;
+ for (final Map.Entry<TopicPartition, Long> entry :
newOffsetSnapshot.entrySet()) {
+ totalOffsetDelta +=
Math.abs(oldOffsetSnapshot.getOrDefault(entry.getKey(), 0L) - entry.getValue());
+ }
+
+ // when enforcing checkpoint is required, we should overwrite the
checkpoint if it is different from the old one;
+ // otherwise, we only overwrite the checkpoint if it is largely
different from the old one
+ return enforceCheckpoint ? totalOffsetDelta > 0 : totalOffsetDelta >
OFFSET_DELTA_THRESHOLD_FOR_CHECKPOINT;
Review comment:
Sorry I meant the "commit" during suspension: when we suspend a task we
would commit the offsets and in `postCommit` we may write the checkpoint file,
and then when we close the suspended task we may commit again (note the
`prepareCommit` call should return empty offsets since there's nothing new to
commit, but in `postCommit` we would checkpoint the file again, i.e. double
writing checkpoint.
So what I did here is to not enforce checkpointing in `postCommit` during
suspension, and only enforce checkpointing in `postCommit` during closing.
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