如何在 docker-compose 构建的 LEMP 堆栈中插入 dockerized cron 进程

我有一个由这个docker-compos文件构建的LEMP堆栈：

cadvisor:
  image: google/cadvisor:latest
  container_name: lemp_cadvisor
  ports:
    - "8080:8080"
  volumes:
    - "/:/rootfs:ro"
    - "/var/run:/var/run:rw"
    - "/sys:/sys:ro"
    - "/var/lib/docker/:/var/lib/docker:ro"
base:
  build: ./base
  container_name: lemp_base
  volumes:
    - /home/core/server-lemp/www/:/var/www/:rw
phpmyadmin:
  build: ./phpmyadmin
  container_name: lemp_phpmyadmin
  links:
    - base
  volumes:
    - /var/www/phpmyadmin
    - ./phpmyadmin/var/www/phpmyadmin/config.inc.php:/var/www/phpmyadmin/config.inc.php:rw
mariadb:
  build: ./mariadb
  container_name: lemp_mariadb
  environment:
    - MYSQL_ROOT_PASSWORD=pwd
  links:
    - base
  volumes:
    - /var/run/mysqld
    - /home/core/server-lemp/mariadb/:/var/lib/mysql/:rw
    - ./mariadb/etc/mysql/my.cnf:/etc/mysql/my.cnf:ro
ffmpeg:
  build: ./ffmpeg
  container_name: lemp_ffmpeg
  links:
    - base
  volumes:
    - /usr/ffmpeg
cron:
  build: ./cron
  container_name: lemp_cron
  links:
    - base
  volumes:
    - /etc/cron.weekly
    - /etc/cron.d
    - /etc/cron.hourly
    - /etc/cron.daily
    - /etc/cron.monthly
php:
  build: ./php
  container_name: lemp_php
  links:
    - base
  volumes:
    - /var/run/php-fpm
    - ./php/usr/local/php7/etc/php-fpm.conf:/usr/local/php7/etc/php-fpm.conf:ro
    - ./php/usr/local/php7/etc/php.ini:/usr/local/php7/etc/php.ini:ro
    - ./php/usr/local/php7/etc/php-fpm.d/www.conf:/usr/local/php7/etc/php-fpm.d/www.conf:ro
  volumes_from:
    - base
    - phpmyadmin
    - mariadb
    - ffmpeg
    - cron
nginx:
  build: ./nginx
  container_name: lemp_nginx
  links:
    - base
  ports:
    - "80:80"
    - "443:443"
  volumes:
    - /var/cache/nginx
    - ./nginx/etc/nginx/nginx.conf:/etc/nginx/nginx.conf:ro
  volumes_from:
    - php

我的./cron/Dockerfile如下所示：

# Lanti/lempCron
#
# VERSION               1.0.0
FROM lemp_base:latest
MAINTAINER XY <info@domain.com>
LABEL Description="Cron" Vendor="XY" Version="1.0"
RUN apt-get -y update && apt-get -y dist-upgrade '
    && apt-get -y install '
        cron
RUN rm -rf /var/lib/apt/lists/*
CMD ["cron", "-f"]

在 Wordpress 安装中，我使用 WP Crontrol 插件检查正在运行的 cron 作业时，我收到以下错误消息：

There was a problem spawning a call to the WP-Cron system on your site.
This means WP-Cron events on your site may not work. The problem was:
Failed to connect to 127.0.0.1 port 80: Connection refused

我认为由于导致此问题的相同错误，Nginx助手插件中的缓存清除选项也不起作用。