MDEV-4984: Implement MASTER_GTID_WAIT() and @@LAST_GTID.

MASTER_GTID_WAIT() is similar to MASTER_POS_WAIT(), but works with a
GTID position rather than an old-style filename/offset.

@@LAST_GTID gives the GTID assigned to the last transaction written
into the binlog.

Together, the two can be used by applications to obtain the GTID of
an update on the master, and then do a MASTER_GTID_WAIT() for that
position on any read slave where it is important to get results that
are caught up with the master at least to the point of the update.

The implementation of MASTER_GTID_WAIT() is implemented in a way
that tries to minimise the performance impact on the SQL threads,
even in the presense of many waiters on single GTID positions (as
from @@LAST_GTID).

1 files changed, 7 insertions, 1 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 4e6646feead..ebfa238df3f 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -780,6 +780,7 @@ PSI_mutex_key key_LOCK_stats,
   key_LOCK_global_user_client_stats, key_LOCK_global_table_stats,
   key_LOCK_global_index_stats,
   key_LOCK_wakeup_ready, key_LOCK_wait_commit;
+PSI_mutex_key key_LOCK_gtid_waiting;
 
 PSI_mutex_key key_LOCK_prepare_ordered, key_LOCK_commit_ordered;
 
@@ -825,6 +826,7 @@ static PSI_mutex_info all_server_mutexes[]=
   { &key_LOCK_global_index_stats, "LOCK_global_index_stats", PSI_FLAG_GLOBAL},
   { &key_LOCK_wakeup_ready, "THD::LOCK_wakeup_ready", 0},
   { &key_LOCK_wait_commit, "wait_for_commit::LOCK_wait_commit", 0},
+  { &key_LOCK_gtid_waiting, "gtid_waiting::LOCK_gtid_waiting", 0},
   { &key_LOCK_thd_data, "THD::LOCK_thd_data", 0},
   { &key_LOCK_user_conn, "LOCK_user_conn", PSI_FLAG_GLOBAL},
   { &key_LOCK_uuid_short_generator, "LOCK_uuid_short_generator", PSI_FLAG_GLOBAL},
@@ -895,6 +897,7 @@ PSI_cond_key key_RELAYLOG_COND_queue_busy;
 PSI_cond_key key_TC_LOG_MMAP_COND_queue_busy;
 PSI_cond_key key_COND_rpl_thread, key_COND_rpl_thread_pool,
   key_COND_parallel_entry, key_COND_prepare_ordered;
+PSI_cond_key key_COND_wait_gtid;
 
 static PSI_cond_info all_server_conds[]=
 {
@@ -940,7 +943,8 @@ static PSI_cond_info all_server_conds[]=
   { &key_COND_rpl_thread, "COND_rpl_thread", 0},
   { &key_COND_rpl_thread_pool, "COND_rpl_thread_pool", 0},
   { &key_COND_parallel_entry, "COND_parallel_entry", 0},
-  { &key_COND_prepare_ordered, "COND_prepare_ordered", 0}
+  { &key_COND_prepare_ordered, "COND_prepare_ordered", 0},
+  { &key_COND_wait_gtid, "COND_wait_gtid", 0}
 };
 
 PSI_thread_key key_thread_bootstrap, key_thread_delayed_insert,
@@ -1821,6 +1825,7 @@ static void mysqld_exit(int exit_code)
     but if a kill -15 signal was sent, the signal thread did
     spawn the kill_server_thread thread, which is running concurrently.
   */
+  rpl_deinit_gtid_waiting();
   rpl_deinit_gtid_slave_state();
   wait_for_signal_thread_to_end();
   mysql_audit_finalize();
@@ -4201,6 +4206,7 @@ static int init_thread_environment()
 
 #ifdef HAVE_REPLICATION
   rpl_init_gtid_slave_state();
+  rpl_init_gtid_waiting();
 #endif
 
   DBUG_RETURN(0);