Abstract Cookbook Pattern
Overview
What is the Abstract Cookbook Pattern?
RightScale also uses an abstract design pattern across its repository of cookbooks. Although related Chef Lightweight Resources and Providers (LWRP) are typically located in the same cookbook, Chef supports the ability to use resources defined in other cookbooks.
The Abstract Cookbook Pattern consists of two different types of cookbooks.
- Abstract Cookbook - Contains a resource that defines a set of general actions such as initializing, backing up, and restoring a database, as well as a set of recipes that use these actions. (e.g. db) The default.rb recipe in abstract cookbooks sets up the provider and all provider-specific inputs and installs the client. The install_server.rb recipe sets all generic server inputs, includes the default.rb recipe and installs the server.
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Concrete Cookbook - Contains Chef providers that perform the actions for a specific variety of abstract cookbooks. (e.g. db_mysql, db_postgres) and a setup_server.rb recipe that sets up server inputs and hard codes the provider name and version of the server.
To group abstract cookbooks with their concrete cookbooks, each concrete cookbook is prefixed with the name of the abstract cookbook. this repeats throughout our collection with groupings such as "app", "db", "lb", "logging", "repo", etc.
Important! The Abstract Cookbook Pattern is used in ServerTemplatesRightScale's v12 and v13 ServerTemplate releases. See ServerTemplates.
How does RightScale use the Abstract Cookbook Pattern?
Example
RightScale's own Git repository contains several examples of this pattern. (https://github.com/rightscale/rights...ster/cookbooks)
In the example screenshot above, there is a generic cookbook ('db') that contains several recipes that perform the same generic actions on the different types of supported databases (MySQL and PostgreSQL). For example, here are a few of the 'db' cookbook's recipes.
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rightscale / rightscale_cookbooks / db / recipes
- do_appservers_allow.rb - Allows the appropriately tagged application servers to connect the "master" database server.
- do_primary_backup.rb - Creates a primary backup of the database.
In the future, when support is added for a new type of database (e.g. Oracle), the same set of 'db' recipes will be executable on the database server as long as the related abstract cookbook (e.g. db_oracle) is available. The Abstract Cookbook Pattern provides a scalable framework for integrating support for new software and functionality without having to duplicate a large portion of code.
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