Consider the following:
1) balancer emits split decision
2) split compaction starts
3) split decision is revoked
4) emits merge decision
5) completes merge, before compaction in step 2 finishes
After last step, split compaction initiated in step 2 can fail because it works with the global tablet map, rather than the map when the compaction started. With the global state changing under its feet, on merge, the mutation splitting writer will think it's going backwards since sibling tablets are merged.
This problem was also seen when running load-and-stream, where split initiated by the sstable writer failed, split completed, and the unsplit sstable is left in the table dir, causing problems in the restart.
To fix this, let's make split compaction always work with the state when it started, not a global state.
Fixes#24153.
All 2025.* versions are vulnerable, so fix must be backported to them.
- (cherry picked from commit 0c1587473c)
- (cherry picked from commit 68f23d54d8)
Parent PR: #25690Closesscylladb/scylladb#25933
* github.com:scylladb/scylladb:
replica: Fix split compaction when tablet boundaries change
replica: Futurize split_compaction_options()
test: fix flakiness of test_missing_data
e71c8a40a9