MDEV-35397: Fix semisync assertion on slave disconnect/reconnect race - #5578
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MDEV-35397: Fix semisync assertion on slave disconnect/reconnect race#5578nadaelsayed11 wants to merge 1 commit into
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Repl_semi_sync_master::remove_slave() clears the entire active-transaction list when the last semisync client disconnects (with rpl_semi_sync_master_wait_no_slave=0), but unlike switch_off() it never bumped rpl_semi_sync_master_off_times. A transaction parked in commit_trx()'s wait loop tolerates a lone disconnect fine, since its own 'no clients left' guard matches remove_slave()'s. But if a slave reconnects before the waiter re-checks, that guard no longer fires, and the waiter finds its entry missing with off_times unchanged, tripping the DBUG_ASSERT that assumes only switch_off() can cause a missing entry. Bump rpl_semi_sync_master_off_times in remove_slave() too, mirroring switch_off(), so the invariant holds and the waiter takes the intended 'skip the wait' exit instead of asserting.
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Thank you for your contribution! This is a preliminary review.
LGTM. Please stand by for the final review.
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FYI: According to our development cycle we work on bugs In the following periods 15 Mar-30 Apr, 15 Jun-30 Jul, 15 Sep-30 Oct and 15 Dec-31 Jan. So, please, expect to get a review somewhere between these two dates and the goal is to have your PR merged before the second date |
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Repl_semi_sync_master::remove_slave() clears the entire active-transaction list when the last semisync client disconnects (with rpl_semi_sync_master_wait_no_slave=0), but unlike switch_off() it never bumped rpl_semi_sync_master_off_times. A transaction parked in commit_trx()'s wait loop tolerates a lone disconnect fine, since its own 'no clients left' guard matches remove_slave()'s. But if a slave reconnects before the waiter re-checks, that guard no longer fires, and the waiter finds its entry missing with off_times unchanged, tripping the DBUG_ASSERT that assumes only switch_off() can cause a missing entry. Bump rpl_semi_sync_master_off_times in remove_slave() too, mirroring switch_off(), so the invariant holds and the waiter takes the intended 'skip the wait' exit instead of asserting.