add healthcheck for postfix

core/postfix/Dockerfile

@@ -7,8 +7,11 @@ RUN apk add --no-cache postfix postfix-pcre rsyslog \
 
 COPY conf /conf
 COPY start.py /start.py
+COPY health.sh /health.sh
 
 EXPOSE 25/tcp 10025/tcp
 VOLUME ["/data"]
 
 CMD /start.py
+
+HEALTHCHECK CMD /health.sh

core/postfix/health.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+if [ "$(echo QUIT|nc localhost 25|tail -n1|cut -f1 -d ' ')" = "221" ]; then
+	echo "ping successful"
+else
+	echo "ping failed"
+	exit 1
+fi