junrao commented on code in PR #14242:
URL: https://github.com/apache/kafka/pull/14242#discussion_r1373536630
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storage/src/main/java/org/apache/kafka/storage/internals/epoch/LeaderEpochFileCache.java:
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@@ -308,7 +308,14 @@ public void truncateFromEnd(long endOffset) {
if (endOffset >= 0 && epochEntry.isPresent() &&
epochEntry.get().startOffset >= endOffset) {
List<EpochEntry> removedEntries = removeFromEnd(x ->
x.startOffset >= endOffset);
- flush();
+ // We intentionally don't force flushing change to the device
here because:
+ // - To avoid fsync latency
+ // * fsync latency could be huge on a disk glitch, which is
not rare in spinning drives
+ // * This method is called by ReplicaFetcher threads, which
could block replica fetching
+ // then causing ISR shrink or high produce response time
degradation in remote scope on high fsync latency.
+ // - Even when stale epochs remained in LeaderEpoch file due
to the unclean shutdown, it will be handled by
+ // another truncateFromEnd call on log loading procedure so
it won't be a problem
+ flush(false);
Review Comment:
> If we don't call flush here, some entries will remain in the file even
after the log truncation.
That's true. But if we write the new content to the file without flushing,
it seems that those old entries could still exist in the file?
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