MDEV-21526: mysqld_multi no longer works with different server binaries

The problem is caused by the fact that adding the
--defaults-group-suffix option to fix MDEV-18863 causes
mysqld to read all options from the appropriate sections
of the config file, including options specific to mysqld_multi.
Reading unknown options (which are not supported by mysqld)
causes mysqld to terminate with an error.

However, the MDEV-18863 problem has been completely fixed
by passing options on the command line, and now there is no
need to specify the --defaults-group-suffix option (we just
need to give priority to options passed through the command
line, so as not to break MDEV-18863).

scripts/mysqld_multi.sh

@@ -308,9 +308,7 @@ sub report_mysqlds
 
 sub start_mysqlds()
 {
-  my (@groups, $com, $tmp, $i, @options, $j, $mysqld_found, $suffix_found, $info_sent);
-
-  $suffix_found= 0;
+  my (@groups, $com, $tmp, $i, @options, $j, $mysqld_found, $info_sent);
 
   if (!$opt_no_log)
   {
@@ -349,10 +347,6 @@ sub start_mysqlds()
         $options[$j]= quote_shell_word($options[$j]);
         $tmp.= " $options[$j]";
       }
-      elsif ("--defaults-group-suffix=" eq substr($options[$j], 0, 24))
-      {
-        $suffix_found= 1;
-      }
       else
       {
 	$options[$j]= quote_shell_word($options[$j]);
@@ -369,12 +363,6 @@ sub start_mysqlds()
       $info_sent= 1;
     }
 
-    if (!$suffix_found)
-    {
-      $com.= " --defaults-group-suffix=";
-      $com.= substr($groups[$i],6);
-    }
-
     $com.= $tmp;
 
     if ($opt_wsrep_new_cluster) {

scripts/wsrep_sst_mariabackup.sh

@@ -713,7 +713,8 @@ INNODB_DATA_HOME_DIR=${INNODB_DATA_HOME_DIR:-""}
 if [ ! -z "$INNODB_DATA_HOME_DIR_ARG" ]; then
     INNODB_DATA_HOME_DIR=$INNODB_DATA_HOME_DIR_ARG
 fi
-# if INNODB_DATA_HOME_DIR env. variable is not set, try to get it from my.cnf
+# if no command line arg and INNODB_DATA_HOME_DIR environment variable
+# is not set, try to get it from my.cnf:
 if [ -z "$INNODB_DATA_HOME_DIR" ]; then
     INNODB_DATA_HOME_DIR=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-data-home-dir '')
 fi
@@ -961,17 +962,25 @@ then
 
     ib_home_dir=$INNODB_DATA_HOME_DIR
 
-    # Try to set ib_log_dir from the command line:
-    ib_log_dir=$INNODB_LOG_GROUP_HOME_ARG
-    if [ -z "$ib_log_dir" ]; then
-        ib_log_dir=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-log-group-home-dir "")
+    WSREP_LOG_DIR=${WSREP_LOG_DIR:-""}
+    # Try to set WSREP_LOG_DIR from the command line:
+    if [ ! -z "$INNODB_LOG_GROUP_HOME_ARG" ]; then
+        WSREP_LOG_DIR=$INNODB_LOG_GROUP_HOME_ARG
     fi
-    if [ -z "$ib_log_dir" ]; then
-        ib_log_dir=$(parse_cnf --mysqld innodb-log-group-home-dir "")
+    # if no command line arg and WSREP_LOG_DIR is not set,
+    # try to get it from my.cnf:
+    if [ -z "$WSREP_LOG_DIR" ]; then
+        WSREP_LOG_DIR=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-log-group-home-dir '')
     fi
+    if [ -z "$WSREP_LOG_DIR" ]; then
+        WSREP_LOG_DIR=$(parse_cnf --mysqld innodb-log-group-home-dir '')
+    fi
+
+    ib_log_dir=$WSREP_LOG_DIR
 
     # Try to set ib_undo_dir from the command line:
-    ib_undo_dir=$INNODB_UNDO_DIR_ARG
+    ib_undo_dir=${INNODB_UNDO_DIR_ARG:-""}
+    # if no command line arg then try to get it from my.cnf:
     if [ -z "$ib_undo_dir" ]; then
         ib_undo_dir=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-undo-directory "")
     fi

scripts/wsrep_sst_rsync.sh

@@ -112,10 +112,11 @@ fi
 
 WSREP_LOG_DIR=${WSREP_LOG_DIR:-""}
 # Try to set WSREP_LOG_DIR from the command line:
-if [ -z "$WSREP_LOG_DIR" ]; then
+if [ ! -z "$INNODB_LOG_GROUP_HOME_ARG" ]; then
     WSREP_LOG_DIR=$INNODB_LOG_GROUP_HOME_ARG
 fi
-# if WSREP_LOG_DIR env. variable is not set, try to get it from my.cnf
+# if no command line arg and WSREP_LOG_DIR is not set,
+# try to get it from my.cnf:
 if [ -z "$WSREP_LOG_DIR" ]; then
     WSREP_LOG_DIR=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-log-group-home-dir '')
 fi
@@ -136,7 +137,8 @@ INNODB_DATA_HOME_DIR=${INNODB_DATA_HOME_DIR:-""}
 if [ ! -z "$INNODB_DATA_HOME_DIR_ARG" ]; then
     INNODB_DATA_HOME_DIR=$INNODB_DATA_HOME_DIR_ARG
 fi
-# if INNODB_DATA_HOME_DIR env. variable is not set, try to get it from my.cnf
+# if no command line arg and INNODB_DATA_HOME_DIR environment variable
+# is not set, try to get it from my.cnf:
 if [ -z "$INNODB_DATA_HOME_DIR" ]; then
     INNODB_DATA_HOME_DIR=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-data-home-dir '')
 fi

scripts/wsrep_sst_xtrabackup-v2.sh

@@ -904,7 +904,8 @@ INNODB_DATA_HOME_DIR=${INNODB_DATA_HOME_DIR:-""}
 if [ ! -z "$INNODB_DATA_HOME_DIR_ARG" ]; then
     INNODB_DATA_HOME_DIR=$INNODB_DATA_HOME_DIR_ARG
 fi
-# if INNODB_DATA_HOME_DIR env. variable is not set, try to get it from my.cnf
+# if no command line arg and INNODB_DATA_HOME_DIR environment variable
+# is not set, try to get it from my.cnf:
 if [ -z "$INNODB_DATA_HOME_DIR" ]; then
     INNODB_DATA_HOME_DIR=$(parse_cnf mysqld$WSREP_SST_OPT_SUFFIX_VALUE innodb-data-home-dir '')
 fi