Whenever is a Ruby gem that provides a clear syntax for writing and deploying cron jobs.

https://github.com/javan/whenever

 (1)首先安装这个gem

$ gem install whenever

(2)将这个gem添加到Gemfile里

Or with Bundler in your Gemfile.

gem 'whenever', :require => false

(3)运行以下命令,This will create an initial config/schedule.rb file for you.

$ wheneverize .

 

(4)编辑定时任务schedule.rb:

every 1.day, at: '00:01 am' do  command "cd /opt/app/ruby/cms/current && RAILS_ENV=#{@environment} bundle exec rails runner script/fetch_video.rb", output: 'log/fetch.log'end

以上含义是在每天晚上12:01执行脚本, (5)想以contab的形式查看schedule.rb脚本,执行以下命令

$ whenever

19:23 [root@a03.test.3g.b28.youku]$ whenever --helpUsage: whenever [options]    -i [identifier],                 Default: full path to schedule.rb file        --update-crontab    -w, --write-crontab [identifier] Default: full path to schedule.rb file    -c, --clear-crontab [identifier]    -s, --set [variables]            Example: --set 'environment=staging&path=/my/sweet/path'    -f, --load-file [schedule file]  Default: config/schedule.rb    -u, --user [user]                Default: current user    -k, --cut [lines]                Cut lines from the top of the cronfile    -r, --roles [role1,role2]        Comma-separated list of server roles to generate cron jobs for    -v, --version

更新写入crontab

$whenever -i

在script里的脚本可以只写功能语句,好处就是与执行时间分离开了,更加达到解偶的效果. (6)如果想立即执行脚本,也不需要去该fetch_video.rb里的代码,直接运行命令:

RAILS_ENV=production rails runner script/fetch_videos.rb

本地环境可以省略前面的RAILS_ENV配置,因为默认就是development环境

(7)部署的时候需要注意在  "config/deploy.rb" file加上:

require "whenever/capistrano"

set :whenever_command, "bundle exec whenever"

(8)最后,部署完在服务器上查看一下

$ crontab -l