cron rake在ror下的使用whenever gem进行简化

whenever enhanced cron on rails way

初始

Getting started

$ cd /my/rails/app
$ wheneverize .

生成cron代码

The `whenever` command

$ cd /my/rails/app
$ whenever

This will simply show you your schedule.rb file converted to cron syntax. It does not read or write your crontab file. Run whenever --help for a complete list of options.

部署

将部署代码集成进capistrano

set :whenever_command, "bundle exec whenever"
require "whenever/capistrano"

放到最后,因为至少要先安装上whenever gem first

其它重要的操作

rails 使用 whenever

rails whenever使用

参考：
https://github.com/javan/whenever 作者：javan javan / whenever
http://myrev.javaeye.com/blog/830164 作者：myrev Rails3利用whenever gem调度发送邮件
http://asciicasts.com/episodes/164-cron-in-ruby Cron in Ruby

whenever用于提供用户的定时任务，在linux下写crontab

1. 安装
$ gem install whenever
或在Gemfile中添加
gem 'whenever', :require => false

2. 在项目目录下
$ cd ~/workspace/deploy
$ wheneverize .
输出：

[add] writing `./config/schedule.rb'
[done] wheneverized!

即创建 config/schedule.rb配置文件

3. 在schedule.rb中写入自己需要定时运行的任务：
如：
every 1.day do
rake "log:clear"
end

4. 运行whenever命令，查看生成的crontab命令
$ whenever
=> 0 0 * * * /bin/bash -l -c 'cd /home/user01/workspace/deploy && RAILS_ENV=production rake log:clear --silent'

可以看到默认环境为生产环境

5. 写入到crontab中：
$ whenever -s environment=development -w /home/user01/workspace/deploy/config/schedule.rb
=> [write] crontab file written

其中environment后为项目运行环境，-w后为schedule.rb的默认路径

6. 更新crontab
$ whenever -i

7. 查看crontab
$ crontab -l

=>

Begin Whenever generated tasks for: /home/user01/workspace/deploy/config/schedule.rb
0 0 * * * /bin/bash -l -c 'cd /home/user01/workspace/deploy && RAILS_ENV=production rake log:clear --silent'
# End Whenever generated tasks for: /home/user01/workspace/deploy/config/schedule.rb

8.清除crontab为：
$ whenever -c

other info

Setting variables on the fly

If you wish to override variables in your schedule.rb file at runtime you can do so using the --set option. This is especially useful for changing your environment when deploying to a staging server or something similar.

Example:

whenever --set environment=staging

You can set more than one variable by forming a query string. Make sure to use quotes.

whenever --set 'environment=staging&cron_log=/my/other/log.txt'

A couple of notes:

Be aware of escaping and/or quoting when using --set with multiple key/value pairs (in other words, be careful with the “&”).
Use --set cron_log=PATH from the command-line to override any set :output, PATH calls in your schedule.rb (--set output=PATH DOESNOT work).

So you can define different tasks per environment:

case @environment
when 'production'
  every 1.day, :at => "#{Time.parse('12:00 A').getlocal.strftime("%H:%M")}" do
    runner "Company.send_later(:create_daily_stories!)"
  end 
when 'staging'
  every 15.minutes do
    command "thinking_sphinx_searchd  reindex"
  end
end

In some situations, you must set the environment with a separate bash command, as seen in this cap task:


  desc "Update the crontab file"
  task :update_crontab, :roles => :db do
    run "cd #{release_path}; whenever --set environment=staging; whenever --update-crontab #{application}"
  end

启用cron 日志

2009-08-21

Ubuntu下Cron Log的启用设置

文章分类:操作系统

原文

调试Cron脚本的时候遇到了一些问题，当我去查看Cron Log文件时竟然发现不存在，我很震惊。

默认情况下，Ubuntu Linux不启用Cron Log。

下面的几个步骤启用Cron Log让我们更好的调试Cron：

编辑 /etc/syslog.conf，并且打开以cron.*开始的那行注释。
运行 /etc/init.d/sysklogd restart 。
运行 /etc/init.d/cron restart 。

即可。

以上错误,

0down vote

By default the cron log in ubuntu is located at /var/log/syslog. Use the below command to check the cron entries in this file.

grep cron /var/log/syslog

Advanced Crontab

The Crontabs discussed above are user crontabs. Each of the above crontabs is associated with a user, even the systemcrontab which is associated with the root user. There are two other types of crontab.

Firstly, as mentioned above anacron uses the run-parts command and /etc/cron.hourly, /etc/cron.weekly, and/etc/cron.monthly directories. However anacron itself is invoked from the /etc/crontab file. This file could be used for other cron commands, but probably shouldn't be. Here's an example line from a ficticious /etc/crontab:

00 01 * * * rusty /home/rusty/rusty-list-files.sh

This would run Rusty's command script as user rusty from his home directory. However, it is not usual to add commands to this file. While an experienced user should know about it, it is not recommended that you add anything to /etc/crontab. Apart from anything else, this could cause problem if the /etc/crontab file is affected by updates! Rusty could lose his command.

The second type of crontab is to be found in /etc/cron.d. Within the directory are small named crontabs. The directory is often used by packages, and the small crontabs allows a user to be associated with the commands in them.

Instead of adding a line to /etc/crontab which Rusty knows is not a good idea, Rusty might well add a file to /etc/cron.d with the name rusty, containing his cron line above. This would not be affected by updates but is a well known location.

When would you use these alternate crontab locations? Well, on a single user machine or a shared machine such as a school or college server, a user crontab would be the way to go. But in a large IT department, where several people might look after a server, then /etc/cron.d is probably the best place to install crontabs - it's a central point and saves searching for them!

You may not need to look at /etc/crontab or /etc/cron.d, let alone edit them by hand. But an experienced user should perhaps know about them and that the packages that he/she installs may use these locations for their crontabs.

Special strings

Cron also offers some special strings:

string	meaning
@reboot	Run once, at startup.
@yearly	Run once a year, "0 0 1 1 *".
@annually	(same as @yearly)
@monthly	Run once a month, "0 0 1 * *".
@weekly	Run once a week, "0 0 * * 0".
@daily	Run once a day, "0 0 * * *".
@midnight	(same as @daily)
@hourly	Run once an hour, "0 * * * *".

Usage: "@reboot /path/to/execuable1" will execute /path/to/executable1 when the system starts. See "man 5 crontab" for more info.

cron howto

https://help.ubuntu.com/community/CronHowto

all relevent information is included in http://blog.scoutapp.com/articles/2010/09/07/rvm-and-cron-in-production

https://github.com/javan/whenever/issues/issue/88

echo $GEM_PATH

/home/mlzboy/.rvm/gems/ruby-1.9.2-p0:/home/mlzboy/.rvm/gems/ruby-1.9.2-p0@global

It seems this is what RVM looks for and is missing because cron does not load your home environment.

Ref: http://adminschoice.com/crontab-quick-reference

You can see what RVM has set the GEM_PATH to by running:

echo $GEM_PATH

http://wiki.joyent.com/smartmachine:rails:cron

http://blog.scoutapp.com/articles/2010/09/07/rvm-and-cron-in-production

http://hectcastro.me/post/722196371/rvm-and-cron

Trading Fish

My name is Hector Castro and I am software developer atWharton Research Data Services, located in Philadelphia, PA. Check out the RSS feeds I monitor, myGitHub account, and an archive of my blog entries.

You can get in contact with me via Twitter orE-mail.

ARCHIVE / RSS

2010-06-21
RVM and Cron
Recently I found myself having to execute a cronjob using specific rubies and gemsets contained within RVM. The following snippet is what I used as a solution:
```
@hourly bash -l -c 'rvm use rbx@gemset && rake cron'
```
The -l forces bash to act as if it had been invoked as a login shell. The -c tells it to read the string that follows.