Chef 简明教程

Chef - Libraries

Chef 中的库提供了一个可以封装已编译逻辑的位置，以便代码整洁美观。

Libraries in Chef provides a place to encapsulate compiled logic so that the cookbook recipes remain neat and clean.

Creating the Library

Step 1 − 在代码的库中创建帮助方法。

Step 1 − Create a helper method in cookbook’s library.

vipin@laptop:~/chef-repo $ subl cookbooks/my_cookbook/libraries/ipaddress.rb
class Chef::Recipe
def netmask(ipaddress)
IPAddress(ipaddress).netmask
end
end

Step 2 − 使用帮助方法。

Step 2 − Use the helper method.

vipin@laptop:~/chef-repo $ subl cookbooks/my_cookbook/recipes/default.rb
ip = '10.10.0.0/24'
mask = netmask(ip) # here we use the library method
Chef::Log.info("Netmask of #{ip}: #{mask}")

Step 3 − 将修改后的代码提交到 Chef 服务器。

Step 3 − Upload the modified cookbook to the Chef Server.

vipin@laptop:~/chef-repo $ knife cookbook upload my_cookbook
Uploading my_cookbook [0.1.0]

Testing the Library

user@server $ sudo chef-client
...TRUNCATED OUTPUT...
[2013-01-18T14:38:26+00:00] INFO: Netmask of 10.10.0.0/24:
255.255.255.0
...TRUNCATED OUTPUT...

Working Method

Chef 库代码可以打开 chef::Recipe 类，并添加新方法（如步骤 1 中所示）。这不是最干净的步骤，但这是最简单的方法。

Chef library code can open the chef::Recipe class and add new methods as done in Step 1. This step is not the cleanest but the simplest way of doing it.

class Chef::Recipe
def netmask(ipaddress)
...
end
end

Best Practices

一旦我们打开 chef::recipe 类，就有可能污染该类。最佳做法是，通常最好在库中引入一个新的子类，并定义一个类方法作为方法。这样可以避免拉取 chef::recipe 命名空间。

Once we open the chef::recipe class, there are changes that it gets polluted. As a best practice, it is always a better way to introduce a new sub class inside the library and define a method as class method. This avoids pulling the chef::recipe namespace.

vipin@laptop:~/chef-repo $ subl cookbooks/my_cookbook/libraries/ipaddress.rb
class Chef::Recipe::IPAddress
def self.netmask(ipaddress)
IPAddress(ipaddress).netmask
end
end

我们可以在代码中使用如下方法：

We can use the method inside the recipe like

IPAddress.netmask(ip)