AI conflict resolution: source PR #4104

Avoid offloading writes to IO threads for the slot migration export job while snapshotting.

1 conflicted file

Claude Summary

Both conflicts are resolved and the result matches the upstream PR exactly in size and shape (28 insertions, 9 deletions across the same 3 files). I did not run git add, per the constraints, so the test file still shows as unmerged in git status — but its contents are fully resolved with no conflict markers.

What I did:

• tests/unit/cluster/cluster-migrateslots.tcl — Both conflicts were on start_cluster header lines for the two slot-migration-max-failover-repl-bytes test blocks. The PR's only change to those lines was adding the network tag; the repl-timeout 3600 override on the incoming side came from an unrelated upstream commit that isn't on the 9.1 branch. I merged by adding just the network tag while keeping 9.1's existing overrides (no repl-timeout 3600), consistent with the other seven start_cluster headers that auto-merged cleanly with only the tag added.

• src/cluster_migrateslots.c and src/io_threads.c — Auto-merged identically to the upstream diff (skip SIGUSR1 when the child exit pipe is closed, defer snapshotting while client IO state isn't idle, and skip IO-thread write offload for slot-migration export clients). No adaptation needed.

Verification: I confirmed all symbols the new code relies on exist on 9.1 (clusterSlotMigrationShouldInstallWriteHandler, slot_migration_child_exit_pipe, io_read_state/io_write_state, CLIENT_IDLE, and the network tag which is recognized in test_helper.tcl and already used by other test files). Both C files pass gcc -fsyntax-only, and no conflict markers remain in any of the three files.

AI-resolved conflicted files

• tests/unit/cluster/cluster-migrateslots.tcl — view diff

Full backport commit diff: commit 270c167226a6.

Please review these AI resolutions for correctness before merging.

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.72%. Comparing base (d27f9ba) to head (abd8e4a).

@@            Coverage Diff             @@
##              9.1    #4225      +/-   ##
==========================================
+ Coverage   76.67%   76.72%   +0.04%     
==========================================
  Files         163      163              
  Lines       81286    81302      +16     
==========================================
+ Hits        62330    62376      +46     
+ Misses      18956    18926      -30