add healthcheck for http services

webmails/roundcube/Dockerfile

@@ -3,7 +3,7 @@ FROM php:7.2-apache
 ENV ROUNDCUBE_URL https://github.com/roundcube/roundcubemail/releases/download/1.3.7/roundcubemail-1.3.7-complete.tar.gz
 
 RUN apt-get update && apt-get install -y \
-      zlib1g-dev \
+      zlib1g-dev curl \
  && docker-php-ext-install zip \
  && echo date.timezone=UTC > /usr/local/etc/php/conf.d/timezone.ini \
  && rm -rf /var/www/html/ \
@@ -28,3 +28,5 @@ EXPOSE 80/tcp
 VOLUME ["/data"]
 
 CMD ["/start.sh"]
+
+HEALTHCHECK CMD curl -f -L http://localhost/ || exit 1