scripts/qemu-guest-agent/fsfreeze-hook.d/mysql-flush.sh.sample

   1 #!/bin/sh
   2
   3 # Flush MySQL tables to the disk before the filesystem is frozen.
   4 # At the same time, this keeps a read lock in order to avoid write accesses
   5 # from the other clients until the filesystem is thawed.
   6
   7 MYSQL="/usr/bin/mysql"
   8 MYSQL_OPTS="-uroot" #"-prootpassword"
   9 FIFO=/var/run/mysql-flush.fifo
  10
  11 # Check mysql is installed and the server running
  12 [ -x "$MYSQL" ] && "$MYSQL" $MYSQL_OPTS < /dev/null || exit 0
  13
  14 flush_and_wait() {
  15     printf "FLUSH TABLES WITH READ LOCK \\G\n"
  16     trap 'printf "$(date): $0 is killed\n">&2' HUP INT QUIT ALRM TERM
  17     read < $FIFO
  18     printf "UNLOCK TABLES \\G\n"
  19     rm -f $FIFO
  20 }
  21
  22 case "$1" in
  23     freeze)
  24         mkfifo $FIFO || exit 1
  25         flush_and_wait | "$MYSQL" $MYSQL_OPTS &
  26         # wait until every block is flushed
  27         while [ "$(echo 'SHOW STATUS LIKE "Key_blocks_not_flushed"' |\
  28                  "$MYSQL" $MYSQL_OPTS | tail -1 | cut -f 2)" -gt 0 ]; do
  29             sleep 1
  30         done
  31         # for InnoDB, wait until every log is flushed
  32         INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
  33         [ $? -ne 0 ] && exit 2
  34         trap "rm -f $INNODB_STATUS; exit 1" HUP INT QUIT ALRM TERM
  35         while :; do
  36             printf "SHOW ENGINE INNODB STATUS \\G" |\
  37                 "$MYSQL" $MYSQL_OPTS > $INNODB_STATUS
  38             LOG_CURRENT=$(grep 'Log sequence number' $INNODB_STATUS |\
  39                           tr -s ' ' | cut -d' ' -f4)
  40             LOG_FLUSHED=$(grep 'Log flushed up to' $INNODB_STATUS |\
  41                           tr -s ' ' | cut -d' ' -f5)
  42             [ "$LOG_CURRENT" = "$LOG_FLUSHED" ] && break
  43             sleep 1
  44         done
  45         rm -f $INNODB_STATUS
  46         ;;
  47
  48     thaw)
  49         [ ! -p $FIFO ] && exit 1
  50         echo > $FIFO
  51         ;;
  52
  53     *)
  54         exit 1
  55         ;;
  56 esac