gem wheneverをdockerで動かす方法

環境

Docker Engine 20.10.2
Ruby 2.7.0
Bundler 2.1.4

手順

wheneverをGemfileへ

# Gemfile

source 'https://rubygems.org'
git_source(:github) do |repo| "https://github.com/#{repo}.git" end

gem 'whenever'

コンテナにcronをインストール

# Dockerfile

FROM ruby:2.7.0

RUN apt-get update && apt-get install -y cron && apt-get install -y vim

WORKDIR /usr/src/app
COPY Gemfile .
COPY Gemfile.lock .
RUN bundle install

コンテナのsetupとwheneverの設定

$ docker build -t test_image .
$ docker create --name="test_container" -it -v "$PWD":/var/src/app test_image
$ docker start test_container
$ docker exec -it test_container /bin/bash
/usr/src/app# bundle exec wheneverize .

以下の設定ファイルができるのでカスタマイズする

# schedule.rb

#
# Use this file to easily define all of your cron jobs.
#
# It's helpful, but not entirely necessary to understand cron before proceeding.
# http://en.wikipedia.org/wiki/Cron

# Example:
#
set :output, "log/cron_log.log"
#
every 1.hours do
  # command
end
#
# every 4.days do
#   runner "AnotherModel.prune_old_records"
# end

# Learn more: http://github.com/javan/whenever

もう一度コンテナに入りコマンドを実行

$ docker exec -it test_container /bin/bash
/usr/src/app# bundle exec whenever
# =>
# 0 0,2,4,6,8,10,12,14,16,18,20,22 * * * /bin/bash -l -c '/usr/bin/some_great_command >> /path/to/my/cron_log.log 2>&1'
# 0 0,2,4,6,8,10,12,14,16,18,20,22 * * * /bin/bash -l -c 'cd /usr/src/app && bundle exec script/runner -e production '\''MyModel.some_method'\'' >> /path/to/my/cron_log.log 2>&1'
# 0 0,2,4,6,8,10,12,14,16,18,20,22 * * * /bin/bash -l -c 'cd /usr/src/app && RAILS_ENV=production bundle exec rake some:great:rake:task --silent >> /path/to/my/cron_log.log 2>&1'
# 0 0 1,5,9,13,17,21,25,29 * * /bin/bash -l -c 'cd /usr/src/app && bundle exec script/runner -e production '\''AnotherModel.prune_old_records'\'' >> /path/to/my/cron_log.log 2>&1'

cronを起動

/usr/src/app# service cron start
#=> [ ok ] Starting periodic command scheduler: cron.

cronが動いているか確認

/usr/src/app# service cron status
#=> [ ok ] cron is running.

参考

gem whenever