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MDEV-7818: Deadlock occurring with parallel replication and FTWRL

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Problem is that FLUSH TABLES WITH READ LOCK first blocks threads from
starting new commits, then waits for running commits to complete. But
in-order parallel replication needs commits to happen in a particular
order, so this can easily deadlock.

To fix this problem, this patch introduces a way to temporarily pause
the parallel replication worker threads. Before starting FTWRL, we let
all worker threads complete in-progress transactions, and then
wait. Then we proceed to take the global read lock. Once the lock is
obtained, we unpause the worker threads. Now commits are blocked from
starting by the global read lock, so the deadlock will no longer occur.
This commit is contained in:
Kristian Nielsen
2015-10-22 11:18:34 +02:00
parent 6d96fab7dd
commit ba02550166
8 changed files with 537 additions and 25 deletions
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3
sql/mysqld.h
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@ -454,6 +454,9 @@ extern PSI_stage_info stage_waiting_for_prior_transaction_to_commit;
extern PSI_stage_info stage_waiting_for_prior_transaction_to_start_commit;
extern PSI_stage_info stage_waiting_for_room_in_worker_thread;
extern PSI_stage_info stage_waiting_for_workers_idle;
extern PSI_stage_info stage_waiting_for_ftwrl;
extern PSI_stage_info stage_waiting_for_ftwrl_threads_to_pause;
extern PSI_stage_info stage_waiting_for_rpl_thread_pool;
extern PSI_stage_info stage_master_gtid_wait_primary;
extern PSI_stage_info stage_master_gtid_wait;
extern PSI_stage_info stage_gtid_wait_other_connection;