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MDEV-29639: Seconds_Behind_Master is incorrect for Delayed, Parallel Replicas

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Problem
========
On a parallel, delayed replica, Seconds_Behind_Master will not be
calculated until after MASTER_DELAY seconds have passed and the
event has finished executing, resulting in potentially very large
values of Seconds_Behind_Master (which could be much larger than the
MASTER_DELAY parameter) for the entire duration the event is
delayed. This contradicts the documented MASTER_DELAY behavior,
which specifies how many seconds to withhold replicated events from
execution.

Solution
========
After a parallel replica idles, the first event after idling should
immediately update last_master_timestamp with the time that it began
execution on the primary.

Reviewed By
===========
Andrei Elkin <andrei.elkin@mariadb.com>
This commit is contained in:
Brandon Nesterenko
2022-11-03 14:56:50 -06:00
parent 2ed598eae8
commit d69e835787
6 changed files with 231 additions and 9 deletions
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3
sql/rpl_parallel.cc
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@ -45,8 +45,7 @@ rpt_handle_event(rpl_parallel_thread::queued_event *qev,
rgi->event_relay_log_pos= qev->event_relay_log_pos;
rgi->future_event_relay_log_pos= qev->future_event_relay_log_pos;
strcpy(rgi->future_event_master_log_name, qev->future_event_master_log_name);
if (!(ev->is_artificial_event() || ev->is_relay_log_event() ||
(ev->when == 0)))
if (event_can_update_last_master_timestamp(ev))
rgi->last_master_timestamp= ev->when + (time_t)ev->exec_time;
err= apply_event_and_update_pos_for_parallel(ev, thd, rgi);