ensure_mysql_is_installed_correctly.sh

#!/bin/bash
#
# This script works on OS X with Homebrew Given a specific MySQL version this
# script will ensure that version is installed, nothing incompatible is
# blocking it from working, and the mysqld process responds to queries.
#
mysql_version=$1
if [[ -z "${mysql_version}" ]]; then
  echo "USAGE: ${0} MYSQL_VERSION_THAT_HOMEBREW_RECOGNIZES"
  echo "example: ${0} mysql@5.5"
  exit 1
fi

set -uo pipefail

main() {
  set +u
  local mysql_version=$1
  set -u

  # Remove all mysql version
  brew services list | egrep 'mysql|percona' | awk '{print $1}' | while read version; do
    brew services stop ${version}
    brew uninstall --force ${version}
  done

  # If MySQL 8 is somehow still listening on port 3306, shut it down
  if echo '' | nc localhost 3306 | grep -q caching_sha2; then
    killall -9 mysqld
  fi

  brew reinstall --force ${mysql_version}
  brew link --force --overwrite ${mysql_version}
  brew services restart ${mysql_version}

  # Wait until mysqld is available, or 30 seconds
  wait_time=0
  until nc -z localhost 3306 || [ $wait_time -eq 30 ]; do
    sleep 1
  done
  sleep 1 # once mysqld is listening, give it a moment to serve queries

  # If myqsld found a data dir from a newer MySQL version, move this directory
  # and reinstall
  log_err_msg="Unknown/unsupported storage engine: InnoDB"
  if grep -q "${log_err_msg}" /usr/local/var/mysql/*.err; then
    dir=/usr/local/var/mysql
    bak=${dir}.bak
    echo "MySQL data dir doesn't work with ${mysql_version}. Moving to '${bak}'"
    rm -rf ${bak}
    mv ${dir} ${bak} 
    mkdir ${dir}

    # Run this whole thing one more time.
    return main ${mysql_version}
  fi

  # Ensure MySQL is actually running and definitely has the right version
  if mysql -u root -e 'select CONCAT("mysql@", @@version)' | grep -q ${mysql_version}; then
    echo "MySQL installation failed! This is unexpected."
    echo "Paste the following output into Slack for help:"
    set -x
    brew services list
    ls -lAG /usr/local/var/mysql*
    ps aux | grep mysq[l]
    set +x
  fi 
}

main $mysql_version