MDEV-19801: Change defaults for CHANGE MASTER TO so that GTID-based replication is used by default if master supports it

This commit makes replicas crash-safe by default by changing the
Using_Gtid value to be Slave_Pos on a fresh slave start and after
RESET SLAVE is issued. If the primary server does not support GTIDs
(i.e., version < 10), the replica will fall back to Using_Gtid=No on
slave start and after RESET SLAVE.

The following additional informational messages/warnings are added:

 1. When Using_Gtid is automatically changed. That is, if RESET
SLAVE reverts Using_Gtid back to Slave_Pos, or Using_Gtid is
inferred to No from a CHANGE MASTER TO given with log coordinates
without MASTER_USE_GTID.
 2. If options are ignored in CHANGE MASTER TO. If CHANGE MASTER TO
is given with log coordinates, yet also specifies
MASTER_USE_GTID=Slave_Pos, a warning message is given that the log
coordinate options are ignored.

Additionally, an MTR macro has been added for RESET SLAVE,
reset_slave.inc, which provides modes/options for resetting a slave
in log coordinate or gtid modes. When in log coordinates mode, the
macro will execute CHANGE MASTER TO MASTER_USE_GTID=No after the
RESET SLAVE command. When in GTID mode, an extra parameter,
reset_slave_keep_gtid_state, can be set to reset or preserve the
value of gtid_slave_pos.

Reviewed By:
===========
Andrei Elkin <andrei.elkin@mariadb.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/sql/sql_repl.cc b/sql/sql_repl.cc
index 90fdce1b56f..d4a455e9034 100644
--- a/sql/sql_repl.cc
+++ b/sql/sql_repl.cc
@@ -3420,6 +3420,16 @@ int reset_slave(THD *thd, Master_info* mi)
     goto err;
   }
 
+  if (mi->using_gtid != Master_info::USE_GTID_SLAVE_POS &&
+      mi->master_supports_gtid)
+  {
+    push_warning_printf(
+        thd, Sql_condition::WARN_LEVEL_NOTE, WARN_OPTION_CHANGING,
+        ER_THD(thd, WARN_OPTION_CHANGING), "RESET SLAVE", "Using_Gtid",
+        mi->using_gtid_astext(mi->using_gtid),
+        mi->using_gtid_astext(Master_info::USE_GTID_SLAVE_POS));
+  }
+
   /* Clear master's log coordinates and associated information */
   mi->clear_in_memory_info(thd->lex->reset_slave_info.all);
 
@@ -3816,7 +3826,41 @@ bool change_master(THD* thd, Master_info* mi, bool *master_info_added)
   else if (lex_mi->use_gtid_opt == LEX_MASTER_INFO::LEX_GTID_NO ||
            lex_mi->log_file_name || lex_mi->pos ||
            lex_mi->relay_log_name || lex_mi->relay_log_pos)
+  {
+    if (lex_mi->use_gtid_opt != LEX_MASTER_INFO::LEX_GTID_NO)
+    {
+      push_warning_printf(
+          thd, Sql_condition::WARN_LEVEL_NOTE, WARN_OPTION_CHANGING,
+          ER_THD(thd, WARN_OPTION_CHANGING), "CHANGE MASTER TO", "Using_Gtid",
+          mi->using_gtid_astext(mi->using_gtid),
+          mi->using_gtid_astext(Master_info::USE_GTID_NO));
+    }
     mi->using_gtid= Master_info::USE_GTID_NO;
+  }
+
+  /*
+    Warn about ignored options if there are GTID/log coordinate option
+    conflicts
+  */
+  if (mi->using_gtid != Master_info::USE_GTID_NO)
+  {
+    if (lex_mi->log_file_name)
+      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                          WARN_OPTION_IGNORED,
+                          ER_THD(thd, WARN_OPTION_IGNORED), "MASTER_LOG_FILE");
+    if (lex_mi->pos)
+      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                          WARN_OPTION_IGNORED,
+                          ER_THD(thd, WARN_OPTION_IGNORED), "MASTER_LOG_POS");
+    if (lex_mi->relay_log_name)
+      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                          WARN_OPTION_IGNORED,
+                          ER_THD(thd, WARN_OPTION_IGNORED), "RELAY_LOG_FILE");
+    if (lex_mi->relay_log_pos)
+      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                          WARN_OPTION_IGNORED,
+                          ER_THD(thd, WARN_OPTION_IGNORED), "RELAY_LOG_POS");
+  }
 
   do_ids= ((lex_mi->repl_do_domain_ids_opt ==
             LEX_MASTER_INFO::LEX_MI_ENABLE) ?