主厨：了解Chef::resource规定？

Question

我正在 https://github.com/chef-cookbooks/mysql/blob/master/libraries/resource_mysql_client.rb 学习关于 mysql 的厨师食谱。

class Chef
  class Resource
    class MysqlClient < Chef::Resource::LWRPBase
      provides :mysql_client

但是，我没看懂provides :mysql_client的意思。有人可以帮我弄清楚代码吗？例如，目的是什么？如果没有线，可以吗？

谢谢

Answer 1

有 a great blog post talking about Chef Provider resolution. I highly recommend you read that first. Historically, Chef has had a number of different ways to figure out which provider should be loaded for a particular resource -- by using a map of resource to provider, by using a class name matching algorithm，最近，如您所述，使用 provides:。

provides意在signal that the class provides a particular DSL object。该方法的评论特别有启发性：

Resources have an automatic DSL based on their resource_name, equivalent to provides :resource_name (providing the resource on all OS's). If you declare a provides with the given resource_name, it replaces that provides (so that you can provide your resource DSL only on certain OS's).

如果您在单个资源 class 和单个提供者 class 上使用提供，Chef（Chef 12.5.x）每次都会将该资源映射到该提供者。如果您省略 provides，您将依赖 Chef 在上面的博客 post 中提到的其他匹配机制之一。几乎所有其他方法都已弃用或即将被弃用。

我也推荐 the Q&A from this blog post。它讨论了旧方法、弃用，并涵盖了提供程序资源解析的其他一些细微差别。

主厨：了解Chef::resource规定？

chef: understanding Chef::resource provides?

ruby

mysql

cookbook

chef-infra