mysql-healthcheck

#!/bin/bash
set -eo pipefail

if [ "$MYSQL_RANDOM_ROOT_PASSWORD" ] && [ -z "$MYSQL_USER" ] && [ -z "$MYSQL_PASSWORD" ]; then
    # there's no way we can guess what the random MySQL password was
    echo >&2 'healthcheck error: cannot determine random root password (and MYSQL_USER and MYSQL_PASSWORD were not set)'
    exit 0
fi

host="$(hostname --ip-address || echo '127.0.0.1')"
user="${MYSQL_USER:-root}"
export MYSQL_PWD="${MYSQL_PASSWORD:-$MYSQL_ROOT_PASSWORD}"

args=(
    # force mysql to not use the local "mysqld.sock" (test "external" connectibility)
    -h"$host"
    -u"$user"
    --silent
)

if command -v mysqladmin &> /dev/null; then
    if mysqladmin "${args[@]}" ping > /dev/null; then
        exit 0
    fi
else
    if select="$(echo 'SELECT 1' | mysql "${args[@]}")" && [ "$select" = '1' ]; then
        exit 0
    fi
fi

exit 1