Very basic mysql health check

mysql-health-check.sh

# A very basic mysql health check that can be used by e.g.
# Consul's External Service Monitor
#
# Cobbled together by @jaygooby from a combination of:
# Unai Rodriguez's and Alex Williams'
# https://gist.github.com/aw/1071144
# and George Chilumbu's
# https://georgechilumbu.wordpress.com/2017/07/27/setup-a-consul-client/
# 
# This script checks if a mysql server is healthy running on $MYSQL_HOST. 
# It will exit with 0 if successful or with an error if not.
#
# It is recommended that a low-privileged-mysql user is created to be used by
# this script. Something like this:
#
# mysql> GRANT SELECT on mysql.* TO 'mysqlhealthcheck'@'localhost' \
#     -> IDENTIFIED BY 'supersecretpassword' WITH GRANT OPTION;
# mysql> flush privileges;
#

MYSQL_HOST=${MYSQL_HOST:-127.0.0.1}
MYSQL_PORT=${MYSQL_PORT:-3306}
MYSQL_USER=${MYSQL_USER:-mysqlhealthcheck}
MYSQL_PASS=${MYSQL_PASS:-supersecretpassword}

status=$(mysql -u "$MYSQL_USER" -p"$MYSQL_PASS" --host "$MYSQL_HOST" -e "select 1\G" | grep "1: 1");
if [ "$?" -ne 0 ]; then
  echo "Cannot connect to mysql."
  exit 2
elif [[ "$status" != *"1: 1"* ]]; then
  echo "MySQL is running, but cannot connect."
  exit 2
else
  exit 0
fi