我在 Ubuntu 14.04 的 Docker 容器中有一个 Ruby on Rails 应用程序。我使用 Dokku 设置了我的部署，但我不确定如何让我的 cron 作业正常工作。
目前我正在使用when gem，它允许我做一些简单的事情，比如：
every 5.minutes do
runner 'MyModel.run_something'
end
问题是我认为每次部署使用git push dokku master它都会重置容器并将其设置回默认值，从而删除我所有的 cron 计划。
所以我想也许 cron 调度需要在容器之外并在 VM 级别。
无论我做什么，我目前都看不到任何 cron 作业正在运行。以下是我运行crontab -lssh 时发生的情况：
root@dashboard:~# crontab -l
no crontab for root
我对容器虚拟化很陌生，所以如果我跳过了其中的一个关键部分，我很抱歉，但我很困惑。
Whenever probably isn't working because the cron daemon isn't running in your Docker/Dokku container. Docker will only run the processes it is told to, using either a CMD or RUN directive or in a script executed by one of those directives.
The Dokku guys have explicitly said that cron is not supported in Dokku, though without saying why. A quick search for cron in the Dokku, Buildstep and Dokku base image repos brings up no results, so it seems to be the case that Dokku never starts a cron service when building/running an app.
The solutions they suggest are to either set up the cron job on the host machine (as you've already figured out), use a web_based scheduling service, or try Heroku's Scheduler.