MDEV-12179: Per-engine mysql.gtid_slave_pos table

Intermediate commit.

Move the discovery of mysql.gtid_slave_pos* tables into the SQL thread.

This avoids doing things like opening tables and scanning the mysql
schema for tables inside of the START SLAVE statement, which might
interact badly with existing transaction or table locks.

(Even though START SLAVE is documented to implicitly commit any active
transactions, this appears not to be the case in current code).

Table discovery fits naturally in the SQL thread init code, next to
the loading of mysql.gtid_slave_pos state.

mysql-test/suite/rpl/r/rpl_gtid_errorhandling.result

@@ -8,22 +8,26 @@ connection slave;
 include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos CHANGE seq_no seq_no VARCHAR(20);
 START SLAVE;
-ERROR HY000: Failed to open mysql.gtid_slave_pos
 connection master;
 INSERT INTO t1 VALUES (1);
 connection slave;
-CALL mtr.add_suppression("Incorrect definition of table mysql.gtid_slave_pos");
+CALL mtr.add_suppression("Slave: Failed to open mysql.gtid_slave_pos");
+include/wait_for_slave_sql_error.inc [errno=1944]
+include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos CHANGE seq_no seq_no BIGINT UNSIGNED NOT NULL;
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (sub_id, domain_id);
 START SLAVE;
-ERROR HY000: Failed to open mysql.gtid_slave_pos
+include/wait_for_slave_sql_error.inc [errno=1944]
+include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
 START SLAVE;
-ERROR HY000: Failed to open mysql.gtid_slave_pos
+include/wait_for_slave_sql_error.inc [errno=1944]
+include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (sub_id);
 START SLAVE;
-ERROR HY000: Failed to open mysql.gtid_slave_pos
+include/wait_for_slave_sql_error.inc [errno=1944]
+include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (domain_id, sub_id);
 include/start_slave.inc

mysql-test/suite/rpl/t/rpl_gtid_errorhandling.test

@@ -10,28 +10,37 @@ CREATE TABLE t1(a INT PRIMARY KEY) ENGINE=InnoDB;
 --connection slave
 --source include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos CHANGE seq_no seq_no VARCHAR(20);
---error ER_GTID_OPEN_TABLE_FAILED
 START SLAVE;
 
 --connection master
 INSERT INTO t1 VALUES (1);
 
 --connection slave
-CALL mtr.add_suppression("Incorrect definition of table mysql.gtid_slave_pos");
+CALL mtr.add_suppression("Slave: Failed to open mysql.gtid_slave_pos");
+--let $slave_sql_errno=1944
+--source include/wait_for_slave_sql_error.inc
+
+--source include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos CHANGE seq_no seq_no BIGINT UNSIGNED NOT NULL;
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (sub_id, domain_id);
---error ER_GTID_OPEN_TABLE_FAILED
 START SLAVE;
+--let $slave_sql_errno=1944
+--source include/wait_for_slave_sql_error.inc
 
+--source include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
---error ER_GTID_OPEN_TABLE_FAILED
 START SLAVE;
+--let $slave_sql_errno=1944
+--source include/wait_for_slave_sql_error.inc
 
+--source include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (sub_id);
---error ER_GTID_OPEN_TABLE_FAILED
 START SLAVE;
+--let $slave_sql_errno=1944
+--source include/wait_for_slave_sql_error.inc
 
+--source include/stop_slave.inc
 ALTER TABLE mysql.gtid_slave_pos DROP PRIMARY KEY;
 ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (domain_id, sub_id);
 --source include/start_slave.inc

sql/mysqld.cc

@@ -7790,7 +7790,7 @@ static int show_slaves_running(THD *thd, SHOW_VAR *var, char *buff)
   var->type= SHOW_LONGLONG;
   var->value= buff;
 
-  *((longlong *)buff)= any_slave_sql_running();
+  *((longlong *)buff)= any_slave_sql_running(false);
 
   return 0;
 }

sql/rpl_mi.cc

@@ -1558,6 +1558,9 @@ bool give_error_if_slave_running(bool already_locked)
 /**
    any_slave_sql_running()
 
+   @param
+   already_locked  0 if we need to lock, 1 if we have LOCK_active_mi_locked
+
    @return
    0            No Slave SQL thread is running
    #		Number of slave SQL thread running
@@ -1568,26 +1571,28 @@ bool give_error_if_slave_running(bool already_locked)
    hash entries can't be accessed.
 */
 
-uint any_slave_sql_running()
+uint any_slave_sql_running(bool already_locked)
 {
   uint count= 0;
   HASH *hash;
   DBUG_ENTER("any_slave_sql_running");
 
-  mysql_mutex_lock(&LOCK_active_mi);
+  if (!already_locked)
+    mysql_mutex_lock(&LOCK_active_mi);
   if (unlikely(shutdown_in_progress || !master_info_index))
+    count= 1;
+  else
   {
+    hash= &master_info_index->master_info_hash;
+    for (uint i= 0; i< hash->records; ++i)
+    {
+      Master_info *mi= (Master_info *)my_hash_element(hash, i);
+      if (mi->rli.slave_running != MYSQL_SLAVE_NOT_RUN)
+        count++;
+    }
+  }
+  if (!already_locked)
     mysql_mutex_unlock(&LOCK_active_mi);
-    DBUG_RETURN(1);
-  }
-  hash= &master_info_index->master_info_hash;
-  for (uint i= 0; i< hash->records; ++i)
-  {
-    Master_info *mi= (Master_info *)my_hash_element(hash, i);
-    if (mi->rli.slave_running != MYSQL_SLAVE_NOT_RUN)
-      count++;
-  }
-  mysql_mutex_unlock(&LOCK_active_mi);
   DBUG_RETURN(count);
 }
 

sql/rpl_mi.h

@@ -377,7 +377,7 @@ void create_logfile_name_with_suffix(char *res_file_name, size_t length,
 uchar *get_key_master_info(Master_info *mi, size_t *length,
                            my_bool not_used __attribute__((unused)));
 void free_key_master_info(Master_info *mi);
-uint any_slave_sql_running();
+uint any_slave_sql_running(bool already_locked);
 bool give_error_if_slave_running(bool already_lock);
 
 #endif /* HAVE_REPLICATION */

sql/rpl_parallel.cc

@@ -1465,7 +1465,7 @@ rpl_parallel_change_thread_count(rpl_parallel_thread_pool *pool,
   */
   if (!new_count && !force)
   {
-    if (any_slave_sql_running())
+    if (any_slave_sql_running(false))
     {
       DBUG_PRINT("warning",
                  ("SQL threads running while trying to reset parallel pool"));
@@ -1620,7 +1620,7 @@ err:
 int rpl_parallel_resize_pool_if_no_slaves(void)
 {
   /* master_info_index is set to NULL on shutdown */
-  if (opt_slave_parallel_threads > 0 && !any_slave_sql_running())
+  if (opt_slave_parallel_threads > 0 && !any_slave_sql_running(false))
     return rpl_parallel_inactivate_pool(&global_rpl_thread_pool);
   return 0;
 }

sql/rpl_rli.cc

@@ -1917,7 +1917,7 @@ find_gtid_slave_pos_tables(THD *thd)
 {
   int err= 0;
   load_gtid_state_cb_data cb_data;
-  bool any_running;
+  uint num_running;
 
   mysql_mutex_lock(&rpl_global_gtid_slave_state->LOCK_slave_state);
   bool loaded= rpl_global_gtid_slave_state->loaded;
@@ -1949,10 +1949,17 @@ find_gtid_slave_pos_tables(THD *thd)
   if ((err= gtid_pos_auto_create_tables(&cb_data.table_list)))
     goto end;
 
-  any_running= any_slave_sql_running();
+  mysql_mutex_lock(&LOCK_active_mi);
+  num_running= any_slave_sql_running(true);
   mysql_mutex_lock(&rpl_global_gtid_slave_state->LOCK_slave_state);
-  if (!any_running)
+  if (num_running <= 1)
   {
+    /*
+      If no slave is running now, the count will be 1, since this SQL thread
+      which is starting is included in the count. In this case, we can safely
+      replace the list, no-one can be trying to read it without lock.
+    */
+    DBUG_ASSERT(num_running == 1);
     rpl_global_gtid_slave_state->set_gtid_pos_tables_list(cb_data.table_list,
                                                           cb_data.default_entry);
     cb_data.table_list= NULL;
@@ -2012,6 +2019,7 @@ find_gtid_slave_pos_tables(THD *thd)
     }
   }
   mysql_mutex_unlock(&rpl_global_gtid_slave_state->LOCK_slave_state);
+  mysql_mutex_unlock(&LOCK_active_mi);
 
 end:
   if (cb_data.table_list)

sql/slave.cc

@@ -5279,6 +5279,14 @@ pthread_handler_t handle_slave_sql(void *arg)
     if (mi->using_gtid != Master_info::USE_GTID_NO || opt_gtid_strict_mode)
       goto err;
   }
+  /* Re-load the set of mysql.gtid_slave_posXXX tables available. */
+  if (find_gtid_slave_pos_tables(thd))
+  {
+    rli->report(ERROR_LEVEL, thd->get_stmt_da()->sql_errno(), NULL,
+                "Error processing replication GTID position tables: %s",
+                thd->get_stmt_da()->message());
+    goto err;
+  }
 
   /* execute init_slave variable */
   if (opt_init_slave.length)

sql/sql_repl.cc

@@ -3031,10 +3031,6 @@ int start_slave(THD* thd , Master_info* mi,  bool net_report)
   if (check_access(thd, SUPER_ACL, any_db, NULL, NULL, 0, 0))
     DBUG_RETURN(-1);
 
-  /* Re-load the set of mysql.gtid_slave_posXXX tables available. */
-  if (find_gtid_slave_pos_tables(thd))
-    DBUG_RETURN(-1);
-
   create_logfile_name_with_suffix(master_info_file_tmp,
                                   sizeof(master_info_file_tmp),
                                   master_info_file, 0,