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[server] Keep async KV flushes on WAL batch boundaries - #4268
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platinumhamburg merged 7 commits intoSep 14, 2026
Merged
platinumhamburg merged 7 commits into
platinumhamburg merged 7 commits into
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Track pending WAL batch ends through append, recovery, flush completion and truncation. Keep each independently completed native write on whole WAL batches so storage backpressure cannot publish an interior high watermark. Cover native write rejection, retry, byte and entry budgets, duplicate and empty batches, leader HW publication, follower truncation and WAL recovery with real storage tests.
Reuse boxed batch ends and bypass segment scanning for a single WAL batch. Allocate the segment list only when splitting is required. Consolidate byte and entry budget coverage in the real Replica recovery test and retain the complete truncation and recovery scenario.
Accumulate complete WAL batches before checking the soft entry and byte budgets. Remove lookahead batch counters and keep trailing empty batches in the final segment. Verify grouped native writes, partial completion and recovery through real storage tests.
Keep real append/backpressure/retry and WAL recovery/truncation scenarios. Remove duplicate parameter combinations and buffer regressions while retaining existing grouping tests.
Replace the boxed boundary queue and flush snapshots with a flag on the final KV mutation of each confirmed WAL batch. Split directly on marked entries and retain the requested flush target for empty tails. Boundary cleanup follows the existing entry completion and truncation lifecycle.
Name the tail mutation marker explicitly for WAL batches and describe its per-batch call ordering. Name native write budgets as entry and byte targets rather than hard maxima.
Continue writing an existing key after deleting the KV directory so RocksDB surfaces the storage error even when the large WAL batch is applied in one native write. Keep the existing failover and full restored-data assertions.
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Pull request overview
This PR keeps asynchronous KV flush progress aligned with complete WAL batches, preserving high-watermark and recovery correctness.
Changes:
- Tracks WAL batch boundaries during append and recovery.
- Splits native KV writes only at batch boundaries.
- Adds backpressure, recovery, truncation, and segmentation tests.
File summaries
| File | Description |
|---|---|
| fluss-server/src/test/java/org/apache/fluss/server/replica/KvReplicaRestoreITCase.java | Updated as part of this pull request. |
| fluss-server/src/test/java/org/apache/fluss/server/kv/prewrite/KvPreWriteBufferTest.java | Updated as part of this pull request. |
| fluss-server/src/test/java/org/apache/fluss/server/kv/KvTabletTest.java | Updated as part of this pull request. |
| fluss-server/src/test/java/org/apache/fluss/server/kv/KvFlushBatchBoundaryTest.java | Updated as part of this pull request. |
| fluss-server/src/main/java/org/apache/fluss/server/kv/prewrite/KvPreWriteBuffer.java | Updated as part of this pull request. |
| fluss-server/src/main/java/org/apache/fluss/server/kv/KvTablet.java | Updated as part of this pull request. |
| fluss-server/src/main/java/org/apache/fluss/server/kv/KvRecoverHelper.java | Updated as part of this pull request. |
Review details
Suppressed comments (1)
fluss-server/src/test/java/org/apache/fluss/server/kv/KvFlushBatchBoundaryTest.java:180
- The new marker logic has distinct paths for duplicated appends and empty/no-op WAL batches, but this scenario only appends two non-empty batches. Existing tests cover their log generation, not that a duplicate or an empty batch leaves the next independently completed flush at a valid batch boundary; please add a real-storage case covering those paths before relying on this integration test for the recovery/truncation guarantee.
replica.putRecordsToLeader(genKvRecordBatch(rows), null, MergeMode.DEFAULT, 0);
replica.putRecordsToLeader(
genKvRecordBatch(new Object[] {600, "tail"}), null, MergeMode.DEFAULT, 0);
assertThat(replica.getLocalLogEndOffset()).isEqualTo(601);
- Files reviewed: 7/7 changed files
- Comments generated: 1
- Review effort level: Lite
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| newLeaderServer.set(restoreServer); | ||
| return true; | ||
| } | ||
| putRecordBatch(tableBucket, leaderServer, triggerBatch); |
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Track pending WAL batch ends through append, recovery, flush completion and truncation. Keep each independently completed native write on whole WAL batches so storage backpressure cannot publish an interior high watermark.
Cover native write rejection, retry, byte and entry budgets, duplicate and empty batches, leader HW publication, follower truncation and WAL recovery with real storage tests.
Purpose
Linked issue: close #4267
Brief change log
Tests
API and Format
Documentation