MDEV-27669: Add skip-slave-start info message

When a slave does not start up the slave threads on restart,
but not reporting anything to the error log about startup failures
either, this can be due to `skip-slave-start` being set in the
config file(s) or on the command line (and most likely is).

Reviewed-by: Sergei Golubchik <[email protected]>

Author: ParadoxV5

mysql-test/main/skip_slave_start.result

@@ -0,0 +1,7 @@
+CHANGE MASTER TO
+master_host='127.0.0.1', master_user='root', master_ssl_verify_server_cert=0;
+# restart: --skip-slave-start
+FOUND 1 /\[Note\] .*skip-slave-start.*/ in mysqld.1.err
+SELECT Slave_SQL_Running, Slave_IO_Running FROM INFORMATION_SCHEMA.SLAVE_STATUS;
+Slave_SQL_Running	Slave_IO_Running
+No	No

mysql-test/main/skip_slave_start.test

@@ -0,0 +1,14 @@
+# Test `--skip-slave-start`
+
+CHANGE MASTER TO
+master_host='127.0.0.1', master_user='root', master_ssl_verify_server_cert=0;
+
+--let $restart_parameters= --skip-slave-start
+--source include/restart_mysqld.inc # not_embedded
+# Outside of `--skip-slave-start`, `mariadbd` will start the CHANGE MASTER TO
+# above when restarting even though it had no explicit START REPLICA.
+
+--let SEARCH_FILE= `SELECT @@log_error`
+--let SEARCH_PATTERN=\[Note\] .*skip-slave-start.*
+--source include/search_pattern_in_file.inc
+SELECT Slave_SQL_Running, Slave_IO_Running FROM INFORMATION_SCHEMA.SLAVE_STATUS;

sql/slave.cc

@@ -609,7 +609,10 @@ int init_slave()
 
   /* If server id is not set, start_slave_thread() will say it */
 
-  if (active_mi->host[0] && !opt_skip_slave_start)
+  if (opt_skip_slave_start)
+    sql_print_information("Replication not automatically started: "
+                          "--skip-slave-start was specified");
+  else if (active_mi->host[0])
   {
     int error;
     THD *thd= new THD(next_thread_id());