MDEV-10004: Galera's pc.recovery process fails in 10.1 with systemd

Galera recovery process works in two phases. In the first
phase, mysqld is started as non-daemon with --wsrep-recover
to recover and fetch the last logged global transaction ID.
This ID is then used in second phase as the start position
(--wsrep-start-position=XX) to start mysqld as daemon.

As this process was implemented in mysqld_safe script, the
recovery did not work when server was started using systemd.

Fixed by introducing a shell script (wsrep_recovery.sh) that
mimics the first phase of the recovery process.

cmake/systemd.cmake

@@ -55,9 +55,10 @@ MACRO(CHECK_SYSTEMD)
       IF(HAVE_SYSTEMD AND HAVE_SYSTEMD_SD_DAEMON_H AND HAVE_SYSTEMD_SD_LISTEN_FDS
          AND HAVE_SYSTEMD_SD_NOTIFY AND HAVE_SYSTEMD_SD_NOTIFYF)
         ADD_DEFINITIONS(-DHAVE_SYSTEMD)
-        SET(SYSTEMD_SCRIPTS mariadb-service-convert galera_new_cluster)
+        SET(SYSTEMD_SCRIPTS mariadb-service-convert galera_new_cluster galera_recovery)
         SET(SYSTEMD_DEB_FILES "usr/bin/mariadb-service-convert
                                usr/bin/galera_new_cluster
+                               usr/bin/galera_recovery
                                ${INSTALL_SYSTEMD_UNITDIR}/mariadb.service
                                ${INSTALL_SYSTEMD_UNITDIR}/mariadb@.service
                                ${INSTALL_SYSTEMD_UNITDIR}/mariadb@bootstrap.service.d/use_galera_new_cluster.conf")

scripts/galera_recovery.sh

+#!/bin/sh
+
+# Copyright (c) 2016 MariaDB Corporation
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+
+# This script is intended to be executed by systemd. It starts mysqld with
+# --wsrep-recover to recover from a non-graceful shutdown, determines the
+# last stored global transaction ID and echoes it in --wsrep-start-position=XX
+# format. The output is then captured and used by systemd to start mysqld.
+# If the server was configured to start without wsrep, nothing is echoed.
+
+cmdline_args=$@
+user="@MYSQLD_USER@"
+print_defaults="@bindir@/my_print_defaults"
+log_file=$(mktemp /tmp/wsrep_recovery.XXXXXX)
+euid=$(id -u)
+recovered_pos=""
+skipped=""
+start_pos=""
+start_pos_opt=""
+ret=0
+wsrep_on=0
+
+log ()
+{
+  local msg="$1"
+  # Print all messages to stderr as we reserve stdout for printing
+  # --wsrep-start-position=XXXX.
+  echo "$msg" >&2
+}
+
+finish()
+{
+  rm -f "$log_file"
+}
+
+trap finish EXIT
+
+parse_arguments() {
+  for arg do
+    val=`echo "$arg" | sed -e "s;--[^=]*=;;"`
+    case "$arg" in
+      --wsrep[-_]on) wsrep_on=1 ;;
+      --skip[-_]wsrep[-_]on) wsrep_on=0 ;;
+      --wsrep[-_]on=*)
+        if echo $val | grep -iq '\(ON\|1\)'; then
+          wsrep_on=1
+        else
+          wsrep_on=0
+        fi
+        ;;
+    esac
+  done
+}
+
+wsrep_recover_position() {
+  # Redirect server's error log to the log file.
+  eval /usr/sbin/mysqld $cmdline_args --user=$user --wsrep_recover 2> "$log_file"
+  ret=$?
+  if [ $ret -ne 0 ]; then
+    # Something went wrong, let us also print the error log so that it
+    # shows up in systemctl status output as a hint to the user.
+    log "WSREP: Failed to start mysqld for wsrep recovery: '`cat $log_file`'"
+    exit 1
+  fi
+
+  # Parse server's error log for recovered position. The server prints
+  # "..skipping position recovery.." if started without wsrep.
+
+  recovered_pos="$(grep 'WSREP: Recovered position:' $log_file)"
+
+  if [ -z "$recovered_pos" ]; then
+    skipped="$(grep WSREP $log_file | grep 'skipping position recovery')"
+    if [ -z "$skipped" ]; then
+      log "WSREP: Failed to recover position: '`cat $log_file`'"
+      exit 1
+    else
+      log "WSREP: Position recovery skipped."
+    fi
+  else
+    start_pos="$(echo $recovered_pos | sed 's/.*WSREP\:\ Recovered\ position://' \
+                    | sed 's/^[ \t]*//')"
+    log "WSREP: Recovered position $start_pos"
+    start_pos_opt="--wsrep_start_position=$start_pos"
+  fi
+}
+
+# Safety checks
+if [ -n "$log_file" -a -f "$log_file" ]; then
+  [ "$euid" = "0" ] && chown $user $log_file
+      chmod 600 $log_file
+else
+  log "WSREP: mktemp failed"
+fi
+
+parse_arguments `$print_defaults $cmdline_args --loose-verbose \
+ mariadb mariadb_safe mysqld mysqld_safe safe_mysqld galera`
+
+# Perform wsrep position recovery if wsrep_on=1, skip otherwise.
+if [ "$wsrep_on" -eq 1 ]; then
+  wsrep_recover_position
+fi
+
+echo "$start_pos_opt"
+

support-files/mariadb.service.in

@@ -48,6 +48,14 @@ CapabilityBoundingSet=CAP_IPC_LOCK
 # Execute pre and post scripts as root, otherwise it does it as User=
 PermissionsStartOnly=true
 
+# Perform automatic wsrep recovery. When server is started without wsrep,
+# galera_recovery simply returns an empty string. In any case, however,
+# the script is not expected to return with a non-zero status.
+# It is always safe to unset _WSREP_START_POSITION environment variable.
+ExecStartPre=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION"
+ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] && \
+ systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1"
+
 # Needed to create system tables etc.
 # ExecStartPre=/usr/bin/mysql_install_db -u mysql
 
@@ -57,9 +65,12 @@ PermissionsStartOnly=true
 # This isn't a replacement for my.cnf.
 # _WSREP_NEW_CLUSTER is for the exclusive use of the script galera_new_cluster
 @SYSTEMD_EXECSTARTPRE@
-ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER
+ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION
 @SYSTEMD_EXECSTARTPOST@
 
+# Unset _WSREP_START_POSITION environment variable.
+ExecStartPost=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION"
+
 KillMode=process
 KillSignal=SIGTERM
 

support-files/mariadb@.service.in

@@ -55,6 +55,21 @@ CapabilityBoundingSet=CAP_IPC_LOCK
 # Execute pre and post scripts as root, otherwise it does it as User=
 PermissionsStartOnly=true
 
+# Perform automatic wsrep recovery. When server is started without wsrep,
+# galera_recovery simply returns an empty string. In any case, however,
+# the script is not expected to return with a non-zero status.
+# It is always safe to unset _WSREP_START_POSITION%I environment variable.
+ExecStartPre=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION%I"
+ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery             \
+  --defaults-file=@INSTALL_SYSCONF2DIR@/my%I.cnf`; [ $? -eq 0 ] && \
+  systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
+# Alternate: (remove ConditionPathExists above)
+# use [mysqld.INSTANCENAME] as sections in my.cnf
+#
+#ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery \
+# --defaults-group-suffix=%I`; [ $? -eq 0 ] &&          \
+# systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
+
 # Needed to create system tables etc.
 # ExecStartPre=/usr/bin/mysql_install_db -u mysql
 
@@ -67,12 +82,15 @@ PermissionsStartOnly=true
 # Note: Place $MYSQLD_OPTS at the very end for its options to take precedence.
 
 ExecStart=/usr/sbin/mysqld --defaults-file=@INSTALL_SYSCONF2DIR@/my%I.cnf \
-  $_WSREP_NEW_CLUSTER $MYSQLD_OPTS
+  $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION%I $MYSQLD_OPTS
 # Alternate: (remove ConditionPathExists above)
 # use [mysqld.INSTANCENAME] as sections in my.cnf
 #
 # ExecStart=/usr/sbin/mysqld --defaults-group-suffix=%I \
-# $_WSREP_NEW_CLUSTER $MYSQLD_OPTS
+# $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION%I $MYSQLD_OPTS
+
+# Unset _WSREP_START_POSITION environment variable.
+ExecStartPost=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION%I"
 
 KillMode=process
 KillSignal=SIGTERM