QGA Sample MySQL

gistfile1.txt

#!/bin/sh
# Flush MySQL tables to disk before the filesystem is frozen.
# Keeps a read lock to avoid write accesses from other clients until thawed.

MYSQL="/usr/bin/mysql"
MYSQL_OPTS="-uroot" # "-prootpassword"
FIFO="/var/run/mysql-flush.fifo"

# Check if mysql is installed and the server is running
if ! [ -x "$MYSQL" ] || ! "$MYSQL" $MYSQL_OPTS < /dev/null; then
  exit 0
fi

flush_and_wait() {
  printf "FLUSH TABLES WITH READ LOCK \\G\n"
  trap 'printf "$(date): $0 is killed\n" >&2' HUP INT QUIT ALRM TERM
  read < "$FIFO"
  printf "UNLOCK TABLES \\G\n"
  rm -f "$FIFO"
}

case "$1" in
  freeze)
    mkfifo "$FIFO" || exit 1
    flush_and_wait | "$MYSQL" $MYSQL_OPTS &

    # Wait until every block is flushed
    while [ "$(echo 'SHOW STATUS LIKE "Key_blocks_not_flushed"' | "$MYSQL" $MYSQL_OPTS | tail -1 | cut -f 2)" -gt 0 ]; do
      sleep 1
    done

    # For InnoDB, wait until every log is flushed
    INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
    [ $? -ne 0 ] && exit 2
    trap "rm -f $INNODB_STATUS; exit 1" HUP INT QUIT ALRM TERM
    while :; do
      printf "SHOW ENGINE INNODB STATUS \\G" | "$MYSQL" $MYSQL_OPTS > "$INNODB_STATUS"
      LOG_CURRENT=$(grep 'Log sequence number' "$INNODB_STATUS" | tr -s ' ' | cut -d' ' -f4)
      LOG_FLUSHED=$(grep 'Log flushed up to' "$INNODB_STATUS" | tr -s ' ' | cut -d' ' -f5)
      [ "$LOG_CURRENT" = "$LOG_FLUSHED" ] && break
      sleep 1
    done
    rm -f "$INNODB_STATUS"
    ;;

  thaw)
    [ ! -p "$FIFO" ] && exit 1
    echo > "$FIFO"
    ;;

  *)
    exit 1
    ;;
esac