Run Rails whenever with docker

Motivation

I tried to use whenever which executes Rails regularly, but I decided to do it with docker because it was difficult to manage environment variables and permissions when implementing it directly on Mac.

Prerequisites

The execution environment is as follows ・ Ruby 2.6.3 ・ Rails 5.2.4 · MySQL 8.0.19

Docker related

Dockfile, docker-compose.yml looks like this It's not much different from normal docker settings, but since we use whenever, we've added the settings for installing corn and running cron in the foreground.

FROM ruby:2.6.3
#ruby version specification

#gem installation
RUN apt-get update -qq && \
    apt-get install -y build-essential \ 
                       libpq-dev \        
                       nodejs

#cron installation
RUN apt-get install -y cron 

RUN mkdir /my_app

WORKDIR /my_app

COPY Gemfile /my_app/Gemfile
COPY Gemfile.lock /my_app/Gemfile.lock

RUN gem install bundler
RUN bundle install

COPY . /my_app

#Write crontab with whenever
RUN bundle exec whenever --update-crontab 

#Run cron in the foreground
CMD ["cron", "-f"] 

docker-compose.yml

version: '2'
services:
  db:
    image: mysql:8.0.19
    command: 
      --default-authentication-plugin=mysql_native_password
    volumes:
      - ./mysql-confd:/etc/mysql/conf.d
      - mysql-data:/var/lib/mysql    #For data persistence
    ports:
      - "3306:3306"
    restart: always
    environment:
      MYSQL_ALLOW_EMPTY_PASSWORD: 1
      # MYSQL_DATABASE: app_development
      MYSQL_USER: root
      # MYSQL_PASSWORD: password
      TZ: Asia/Tokyo
  app:
    build: .
    command: bundle exec rails s -p 3000 -b '0.0.0.0'
    volumes:
      - .:/my_app   
      - bundle:/usr/local/bundle   
    ports:
      - "3000:3000"
    links:
      - db

volumes:
  mysql-data:
  bundle:      #You don't have to rebuild after bundle install

whenever relationship

config/schedule.rb

#Rails because you need to start rails whenever.Use root
require File.expand_path(File.dirname(__FILE__) + "/environment")

#It does the environment variables nicely
ENV.each { |k, v| env(k, v) }

#File to write logs
set :output, error: 'log/crontab_error.log', standard: 'log/crontab.log'
set :environment, :development

#Every 2 minutes`sample_task`of`scheduled_task`To run
every 2.minutes do
  rake 'sample_task:scheduled_task'
  # runner "Test.yakisoba", :environment => :development #runner example
end

Command you want to execute

/lib/tasks/sample_task.rb

namespace :sample_task
  desc "scheduled_task"
  task scheduled_task: :environment do
     .....Function you want to execute
    end
  end
end