[backport 3.4] limbo: do not limit its size on replicas#12027
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Gerold103 merged 1 commit intorelease/3.4from Nov 12, 2025
Merged
[backport 3.4] limbo: do not limit its size on replicas#12027Gerold103 merged 1 commit intorelease/3.4from
Gerold103 merged 1 commit intorelease/3.4from
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There was a possible deadlock when a replica had box.cfg.replication_synchro_queue_max_size smaller than the master. The scenario was that the replica would receive some transactions, they would all enter the limbo and wait for CONFIRM in "submitted" state. But the master sends more transactions instead of CONFIRM. Those transactions block the applier fiber in txn_commit_submit(), because the fiber can't exceed the limbo max size and is waiting for free space. The free space however will never appear, because those "submitted" transactions aren't going anywhere until CONFIRM receipt. Which in turn will never happen, because the applier fiber is blocked on waiting for limbo space. The only way is to let the replica apply these transactions bypassing the limbo max size limitation. It makes no sense to block them. Otherwise their CONFIRM can't be received. This was probably working until commit 20aad15 ("limbo: handle spurious wakeups on space waiting") (not counting that before that it was broken in many other ways), but seems like wasn't covered by the tests. Closes #11836 NO_DOC=bugfix (cherry picked from commit cc77a6e)
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(This PR is a backport of #12017 to
release/3.4to a future3.4.2release.)There was a possible deadlock when a replica had
box.cfg.replication_synchro_queue_max_size smaller than the master.
The scenario was that the replica would receive some transactions, they would all enter the limbo and wait for CONFIRM in "submitted" state.
But the master sends more transactions instead of CONFIRM. Those transactions block the applier fiber in txn_commit_submit(), because the fiber can't exceed the limbo max size and is waiting for free space.
The free space however will never appear, because those "submitted" transactions aren't going anywhere until CONFIRM receipt. Which in turn will never happen, because the applier fiber is blocked on waiting for limbo space.
The only way is to let the replica apply these transactions bypassing the limbo max size limitation. It makes no sense to block them. Otherwise their CONFIRM can't be received.
This was probably working until
commit 20aad15 ("limbo: handle spurious wakeups on space waiting") (not counting that before that it was broken in many other ways), but seems like wasn't covered by the tests.
Closes #11836
NO_DOC=bugfix