MDEV-15730: rename --stream=xbstream to --stream=mbstream

mbstream is already supported as a format name after MDEV-24580,
but additional code refactoring has been done to correctly display
the format name in log files and to check if the mbstream utility
is in the path. Also, for xtrabackup-v2 (only available in the 10.2)
both utilities are supported - both xbstram and mbstream, since they
are interchangeable in this context. In this case, the original
innobackupex always receives the correct --stream=xbstream option
as input, but the user can actually try to use the mbstream utility
during the transfer (if the user explicitly specifies this in the
configuration file).

scripts/wsrep_sst_common.sh

@@ -295,7 +295,7 @@ case "$1" in
                                    value="$1"
                                fi
                            fi
-                           if [ $option == 'h' ]; then
+                           if [ $option = 'h' ]; then
                                if [ -z "$WSREP_SST_OPT_DATA" ]; then
                                    MYSQLD_OPT_DATADIR="${value%/}"
                                fi

scripts/wsrep_sst_mariabackup.sh

@@ -55,7 +55,7 @@ ib_home_dir=""
 ib_log_dir=""
 ib_undo_dir=""
 
-sfmt="tar"
+sfmt=""
 strmcmd=""
 tfmt=""
 tcmd=""
@@ -97,7 +97,6 @@ if [ ! -x "$MARIABACKUP_BIN" ]; then
     wsrep_log_error 'mariabackup binary not found in $PATH'
     exit 42
 fi
-MBSTREAM_BIN=mbstream
 
 DATA="$WSREP_SST_OPT_DATA"
 INFO_FILE="xtrabackup_galera_info"
@@ -481,21 +480,26 @@ read_cnf()
 get_stream()
 {
     if [ "$sfmt" = 'mbstream' -o "$sfmt" = 'xbstream' ]; then
-        wsrep_log_info "Streaming with ${sfmt}"
+        sfmt='mbstream'
+        MBSTREAM_BIN="$(command -v mbstream)"
+        if [ -z "$MBSTREAM_BIN" ]; then
+            wsrep_log_error "Streaming with $sfmt, but $sfmt not found in path"
+            exit 42
+        fi
         if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
-            strmcmd="$MBSTREAM_BIN -x"
+            strmcmd="'$MBSTREAM_BIN' -x"
         else
-            strmcmd="$MBSTREAM_BIN -c '$INFO_FILE'"
+            strmcmd="'$MBSTREAM_BIN' -c '$INFO_FILE'"
         fi
     else
-        sfmt="tar"
-        wsrep_log_info "Streaming with tar"
-        if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]]; then
-            strmcmd="tar xfi -"
+        sfmt='tar'
+        if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
+            strmcmd='tar xfi -'
         else
             strmcmd="tar cf - '$INFO_FILE'"
         fi
     fi
+    wsrep_log_info "Streaming with $sfmt"
 }
 
 get_proc()
@@ -930,7 +934,7 @@ setup_commands()
     fi
     INNOAPPLY="$MARIABACKUP_BIN --prepare $disver $iapts $INNOEXTRA --target-dir='$DATA' --datadir='$DATA' $mysqld_args $INNOAPPLY"
     INNOMOVE="$MARIABACKUP_BIN $WSREP_SST_OPT_CONF --move-back $disver $impts --force-non-empty-directories --target-dir='$DATA' --datadir='${TDATA:-$DATA}' $INNOMOVE"
-    INNOBACKUP="$MARIABACKUP_BIN $WSREP_SST_OPT_CONF --backup $disver $iopts $tmpopts $INNOEXTRA --galera-info --stream='$sfmt' --target-dir='$itmpdir' --datadir='$DATA' $mysqld_args $INNOBACKUP"
+    INNOBACKUP="$MARIABACKUP_BIN $WSREP_SST_OPT_CONF --backup $disver $iopts $tmpopts $INNOEXTRA --galera-info --stream=$sfmt --target-dir='$itmpdir' --datadir='$DATA' $mysqld_args $INNOBACKUP"
 }
 
 get_stream

scripts/wsrep_sst_xtrabackup-v2.sh

@@ -48,7 +48,7 @@ ib_home_dir=""
 ib_log_dir=""
 ib_undo_dir=""
 
-sfmt="tar"
+sfmt=""
 strmcmd=""
 tfmt=""
 tcmd=""
@@ -489,22 +489,28 @@ read_cnf()
 
 get_stream()
 {
-    if [[ $sfmt == 'xbstream' ]];then
-        wsrep_log_info "Streaming with xbstream"
-        if [[ "$WSREP_SST_OPT_ROLE" == "joiner" ]];then
-            strmcmd="xbstream -x"
+    if [ "$sfmt" = 'mbstream' -o "$sfmt" = 'xbstream' ]; then
+        XBSTREAM_BIN=$(command -v "$sfmt")
+        if [ -z "$XBSTREAM_BIN" ]; then
+            if [ -z "$XBSTREAM_BIN" ]; then
+                wsrep_log_error "Streaming with $sfmt, but $sfmt not found in path"
+                exit 42
+            fi
+        fi
+        if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
+            strmcmd="'$XBSTREAM_BIN' -x"
         else
-            strmcmd="xbstream -c '${INFO_FILE}'"
+            strmcmd="'$XBSTREAM_BIN' -c '$INFO_FILE'"
         fi
     else
-        sfmt="tar"
-        wsrep_log_info "Streaming with tar"
-        if [[ "$WSREP_SST_OPT_ROLE" == "joiner" ]];then
-            strmcmd="tar xfi -"
+        sfmt='tar'
+        if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
+            strmcmd='tar xfi -'
         else
-            strmcmd="tar cf - '${INFO_FILE}'"
+            strmcmd="tar cf - '$INFO_FILE'"
         fi
     fi
+    wsrep_log_info "Streaming with $sfmt"
 }
 
 get_proc()
@@ -575,7 +581,6 @@ cleanup_donor()
             wsrep_log_error "xtrabackup process is still running. Killing... "
             kill_xtrabackup
         fi
-
     fi
 
     rm -f "${DATA}/${IST_FILE}" || true
@@ -852,7 +857,11 @@ cd "$OLD_PWD"
 setup_commands () {
     INNOAPPLY="$INNOBACKUPEX_BIN $disver $iapts $INNOEXTRA --apply-log $rebuildcmd '$DATA' $INNOAPPLY"
     INNOMOVE="$INNOBACKUPEX_BIN $WSREP_SST_OPT_CONF $disver $impts --move-back --force-non-empty-directories '$DATA' $INNOMOVE"
-    INNOBACKUP="$INNOBACKUPEX_BIN $WSREP_SST_OPT_CONF $disver $iopts $tmpopts $INNOEXTRA --galera-info --stream='$sfmt' '$itmpdir' $INNOBACKUP"
+    sfmt_work="$sfmt"
+    if [ "$sfmt" = 'mbstream' ]; then
+        sfmt_work='xbstream'
+    fi
+    INNOBACKUP="$INNOBACKUPEX_BIN $WSREP_SST_OPT_CONF $disver $iopts $tmpopts $INNOEXTRA --galera-info --stream=$sfmt_work '$itmpdir' $INNOBACKUP"
 }
 
 if [ "$WSREP_SST_OPT_ROLE" = "donor" ]