Configure Dockerfile to Run Cron Tasks using Whenver and Rake - ruby

Question

I want to create a container using Docker which is will be responsible for starting recurrent rake tasks based on the Whenever gem's configuration. I have a plain ruby project (without rails/sinatra) with the following structure:
Gemfile:
source 'https://rubygems.org'
gem 'rake', '~> 12.3', '>= 12.3.1'
gem 'whenever', '~> 0.9.7', require: false
group :development, :test do
gem 'byebug', '~> 10.0', '>= 10.0.2'
end
group :test do
gem 'rspec', '~> 3.5'
end
config/schedule.rb: (whenever's configuration)
ENV.each { |k, v| env(k, v) }
every 1.minutes do
rake 'hello:start'
end
lib/tasks/hello.rb: (rake configuration)
namespace :hello do
desc 'This is a sample'
task :start do
puts 'start something!'
end
end
Dockerfile:
FROM ruby:2.5.3-alpine3.8
RUN echo "http://dl-cdn.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories && \
apk update && apk upgrade && \
apk add build-base bash dcron && \
apk upgrade --available && \
rm -rf /var/cache/apk/* && \
mkdir /usr/app
WORKDIR /usr/app
COPY Gemfile* /usr/app/
RUN bundle install
COPY . /usr/app
RUN bundle exec whenever --update-crontab
CMD ['sh', '-c', 'crond && gulp']
I've used the following resources to get at the this point
How to run a cron job inside a docker container
https://github.com/renskiy/cron-docker-image/blob/master/alpine/Dockerfile
https://stackoverflow.com/a/43622984/5171758 <- very close to I want but no success
If I call my rake task using command line, I get the result I want.
$ rake 'hello:start'
start something!
However, I can't figure out how to make it work using Docker. The container is build but no log is written, no output is shown, nothing happens. Can someone help me showing what I'm doing wrong?
building commands
docker build -t gsc:0.0.1 .
docker container run -a stdin -a stdout -i --net host -t gsc:0.0.1 /bin/bash
Thanks all. Cheers

Answer 1

This is the solution to the problem I listed above. I had some issues at the Dockerfile and schedule.rb. This is what I had to change to make it work correctly.
Dockerfile
wrong echo call
wrong bundle command
change ENTRYPOINT instead of CMD
FROM ruby:2.5.3-alpine3.8
RUN apk add --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/main && \
apk update && apk upgrade && \
apk add build-base bash dcron && \
apk upgrade --available && \
rm -rf /var/cache/apk/* && \
mkdir /usr/app
WORKDIR /usr/app
COPY Gemfile* /usr/app/
RUN bundle install
COPY . /usr/app
RUN bundle exec whenever -c && bundle exec whenever --update-crontab && touch ./log/cron.log
ENTRYPOINT crond && tail -f ./log/cron.log
config/schedule.rb
no need to ENV.each
every 1.minutes do
rake 'hello:start'
end
UPDATE
I've created a GitHub repository and a Docker Hub repository to share with the community this progress.