#!/bin/bash
#
# Scripts to run by MySQL systemd service
#
# Needed argument: pre
#
# pre mode  :  try to perform sanity check for configuration, log, data

# Read a config option from mysql. Note that this will only work if a config
# file actually specifies the option, so it's important to specify a default
# $1 is application (e.g. mysqld for server)
# $2 is option
# $3 is default value used if no config value is found
get_mysql_option() {
        result=$(my_print_defaults "$1" | sed -n "s/^--$2=//p" | tail -n 1)
        if [ -z "$result" ];
        then
                result="$3"
        fi
        echo "$result"
}
sanity () {
  if [ ! -r /etc/mysql/my.cnf ]; then
    echo "MySQL configuration not found at /etc/mysql/my.cnf. Please create one."
    exit 1
  fi
  datadir=$(get_mysql_option mysqld datadir "/var/lib/mysql")
  if [ ! -d "${datadir}" ] && [ ! -L "${datadir}" ]; then
    echo "MySQL data dir not found at ${datadir}. Please create one."
    exit 1
  fi

  if [ ! -d "${datadir}/mysql" ] && [ ! -L "${datadir}/mysql" ]; then
    echo "MySQL system database not found in ${datadir}. Please run mysqld --initialize."
    exit 1
  fi

  # Do a test start to make sure there are no configuration issues or similar
  # mysqld --verbose --help will output a full listing of settings and plugins.
  # To do so it needs to initialize the database, so it can be used as a test
  # for whether or not the server can start. We redirect stdout to /dev/null so
  # only the error messages are left.
  result=0
  output=$(mysqld --verbose --help --innodb-read-only 2>&1 > /dev/null) || result=$?
  if [ ! "$result" = "0" ]; then
    echo "ERROR: Unable to start MySQL server:" >&2
    echo "$output" >&2
    echo "Please take a look at https://wiki.debian.org/Teams/MySQL/FAQ for tips on fixing common upgrade issues." >&2
    echo "Once the problem is resolved, restart the service." >&2
    exit 1
  fi
}

case $1 in
  "pre")  sanity ;;
esac