[WIP] #3812
[WIP] #3812
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Summary of ChangesHello @lidezhu, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly refactors the processing of resolved timestamp (ResolvedTs) events within the log puller component. By introducing a dedicated, configurable worker pool, the system can now handle these events asynchronously and in parallel. This change aims to enhance the efficiency, scalability, and robustness of ResolvedTs event processing, reducing potential bottlenecks in the main event handling pipeline and improving overall system performance. Highlights
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Code Review
This pull request refactors the handling of resolved timestamp (resolvedTs) events by introducing a dedicated worker pool to process them in parallel, aiming to improve performance. The core logic for handleResolvedTs is moved to a new file, and the event handling is updated to accommodate this new asynchronous processing flow. The changes are well-structured and include corresponding test updates.
My review has identified a critical bug that could lead to a panic, and a potential memory leak due to a logic change in cleaning up the event matcher. I've provided suggestions to fix these issues.
| if span == nil { | ||
| span = state.region.subscribedSpan | ||
| } else if span != state.region.subscribedSpan { | ||
| log.Panic("resolved ts event contains multiple spans", | ||
| zap.Uint64("workerID", s.workerID), | ||
| zap.Uint64("subscriptionID", uint64(subscriptionID)), | ||
| zap.Uint64("regionID", regionID)) | ||
| } | ||
| if span == nil { | ||
| log.Warn("region request worker receives a resolved ts event for region without span", | ||
| zap.Uint64("workerID", s.workerID), | ||
| zap.Uint64("subscriptionID", uint64(subscriptionID)), | ||
| zap.Uint64("regionID", regionID)) | ||
| continue | ||
| } |
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The logic to check for consistent spans across regions in a resolved-ts event has a bug. The condition span != state.region.subscribedSpan will cause a panic if span is non-nil and state.region.subscribedSpan is nil. This is incorrect, as it should only panic if they are two different, non-nil spans. This logic is also overly complex. It can be simplified to be more readable and correct.
currentSpan := state.region.subscribedSpan
if currentSpan == nil {
log.Warn("region request worker receives a resolved ts event for region without span",
zap.Uint64("workerID", s.workerID),
zap.Uint64("subscriptionID", uint64(subscriptionID)),
zap.Uint64("regionID", regionID))
continue
}
if span == nil {
span = currentSpan
} else if span != currentSpan {
log.Panic("resolved ts event contains multiple spans",
zap.Uint64("workerID", s.workerID),
zap.Uint64("subscriptionID", uint64(subscriptionID)),
zap.Uint64("regionID", regionID))
}| func handleResolvedTs(span *subscribedSpan, state *regionFeedState, resolvedTs uint64) uint64 { | ||
| if state.isStale() || !state.isInitialized() { | ||
| return 0 | ||
| } |
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The call to state.matcher.tryCleanUnmatchedValue() was present in the original handleResolvedTs function but is missing here. This function was likely responsible for cleaning up stale, unmatched prewrite entries in the matcher using the advancing resolved timestamp as a watermark. By moving this call to handleEventEntries, the matcher will only be cleaned when there are KV events. If a region is idle and only receives resolved timestamp updates, the matcher may not be cleaned, potentially leading to a memory leak of stale prewrite entries. It seems this call should be restored here to prevent this potential memory leak.
| } | |
| } | |
| state.matcher.tryCleanUnmatchedValue() |
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| func handleEventEntries(span *subscribedSpan, state *regionFeedState, entries *cdcpb.Event_Entries_) { | ||
| regionID, _, _ := state.getRegionMeta() | ||
| state.matcher.tryCleanUnmatchedValue() |
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This call was moved here from handleResolvedTs. However, this means the matcher is only cleaned when KV events are processed. If a region is idle and only receives resolved timestamp updates, this could lead to a memory leak of stale prewrite entries. This call should be moved back to handleResolvedTs and removed from here.
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What problem does this PR solve?
Issue Number: close #xxx
What is changed and how it works?
Check List
Tests
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Will it cause performance regression or break compatibility?
Do you need to update user documentation, design documentation or monitoring documentation?
Release note