Writing Chef for Blueprints

Making it Simpler

The example we've just seen shows how existing Chef cookbooks can be used as the basis for entities. If you're writing the Chef recipes, there are a few simple techniques we've established with the Chef community which make blueprints literally as simple as:

- type: chef:mysql
  brooklyn.config:
    mysql_password: p4ssw0rd
    pid_file: /var/run/mysqld/mysqld.pid

Some Basic Conventions

• A start recipe: The first step is to provide a start recipe in recipes/start.rb; if no launch_run_list is supplied, this is what will be invoked to launch the entity. It can be as simple as a one-line file:

  include_recipe 'mysql::server'
  

• Using brooklyn.config: All the brooklyn.config is passed to Chef as node attributes in the node['brooklyn']['config'] namespace. Thus if the required attributes in the mysql recipe are set to take a value set in node['brooklyn']['config']['mysql_password'], you can dispense with the launch_attributes section.

Using Chef Server

The examples so far have not required Chef Server, so they will work without any external Chef dependencies (besides the built-in install from https://www.opscode.com/chef/install.sh and the explicitly referenced cookbooks). If you use Chef Server, however, you'll want your managed nodes to be integrated with it. This is easy to set up, with a few options:

If you have knife set up in your shell environment, the Brooklyn Chef support will use it by default. If the recipes are installed in your Chef server, you can go ahead and remove the cookbooks_url section!

Use of solo or knife can be forced by setting the chef_mode flag (brooklyn.chef.mode config key) to either of those values. (It defaults to autodetect, which will use knife if it is on the path and satisfies sanity checks).

If you want to specify a different configuration, there are a number of config keys you can use:

• brooklyn.chef.knife.executableFile: this should be point to the knife binary to use
• brooklyn.chef.knife.configFile: this should point to the knife configuration to use
• brooklyn.chef.knife.setupCommands: an optional set of commands to run prior to invoking knife, for example to run rvm to get the right ruby version on the Brooklyn server

If you're interested in seeing the Chef REST API be supported directly (without knife), please let us know. We'd like to see this too, and we'll help you along the way!

Tips and Tricks

To help you on your way writing Chef blueprints, here are a handful of pointers particularly useful in this context:

• Configuration keys can be inherited from the top-level and accessed using $brooklyn:entity('id').config('key_name'). An example of this is shown in the mysql-chef.yaml sample recipe contained in the Brooklyn code base and here for convenience. Here, p4ssw0rd is specified only once and then used for all the attributes required by the stock mysql cookbook.

• Github tarball downloads! You'll have noticed these in the example already, but they are so useful we thought we'd call them out again. Except when you're developing, we recommend using specific tagged versions rather than master.

• The usual machine provisioning.properties are supported with Chef blueprints, so you can set things like minRam and osFamily

• To see more configuration options, and understand the ones presented here in more detail, see the javadoc or the code for the class ChefConfig in the Brooklyn code base.