Add "mysql"

mysql/Dockerfile

@@ -0,0 +1,5 @@
+FROM mysql
+
+COPY docker-healthcheck /usr/local/bin/
+
+HEALTHCHECK CMD ["docker-healthcheck"]

mysql/docker-healthcheck

@@ -0,0 +1,27 @@
+#!/bin/bash
+set -eo pipefail
+
+if [ "$MYSQL_RANDOM_ROOT_PASSWORD" ] && [ -z "$MYSQL_USER" ] && [ -z "$MYSQL_PASSWORD" ]; then
+	# there's no way we can guess what the random MySQL password was
+	echo >&2 'healthcheck error: cannot determine random root password (and MYSQL_USER and MYSQL_PASSWORD were not set)'
+	exit 0
+fi
+
+user="${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"$(hostname --ip-address || echo '127.0.0.1')"
+	-u"$user"
+	--silent
+)
+
+if select="$(echo 'SELECT 1' | mysql "${args[@]}")" && [ "$select" = '1' ]; then
+	exit 0
+fi
+
+# If the probe returns 2 ("starting") when the container has already moved out of the "starting" state then it is treated as "unhealthy" instead.
+# https://github.com/docker/docker/blob/dcc65376bac8e73bb5930fce4cddc2350bb7baa2/docs/reference/builder.md#healthcheck
+exit 2