[chef] how to alter a recipe in the simplest, DRYest way?

[Roger Rohrbach < >]

Hi all,

 I'm new to Chef (but not to Opscode—hi guys!).  I'm having trouble discerning the One Right Way to Do It.  Here's a simple example: I want to use NginxHttpRealIpModule.  This entails compiling Nginx with --with-http_realip_module.  Being at the very beginning of my Chef odyssey, I've not yet set up any Roles, so I create site-cookbooks/nginx/attributes/nginx.rb, with these contents:

    set[:nginx][:configure_flags] = [

      "--prefix=#{nginx[:install_path]}",

      "--conf-path=#{nginx[:dir]}/nginx.conf",

      "--with-http_ssl_module",

      "--with-http_gzip_static_module",

      "--with-http_realip_module"

    ]

I'm using Chef 0.7.16.  Since cookbook_path is [ "/srv/chef/site-cookbooks", "/srv/chef/cookbooks" ], I'd expect that this would set [:nginx][:configure_flags], and its value would not be overwritten by the Opscode cookbook attribute setting:

    set_unless[:nginx][:configure_flags] = [

      "--prefix=#{nginx[:install_path]}",

      "--conf-path=#{nginx[:dir]}/nginx.conf",

      "--with-http_ssl_module",

      "--with-http_gzip_static_module"

    ]

But when I install my recipes, execute chef-client on a node that has nginx::source in its run list, and watch it recompile Nginx, it uses the default value of configure_flags.

My next stab is to try to use a Role.  So, I create roles/web-server.rb:

    name "web-server"

    description "Test role for configuring Web servers"

    recipes "nginx::source"

    override_attributes(

      "nginx" => {

        "configure_flags" => [

            "--prefix=#{nginx[:install_path]}",

            "--conf-path=#{nginx[:dir]}/nginx.conf",

            "--with-http_ssl_module",

            "--with-http_gzip_static_module",

            "--with-http_realip_module"

        ]

      }

    )

and run rake roles.  This gives:

    undefined local variable or method `nginx' for #<Chef::Role:0x7fc810f37b60>

because the first two compiler flag definitions reference a Node variable, and there's no Node yet.  I don't know how to reference the value of the install_path or dir defined in cookbooks/nginx/attributes/nginx.rb from this Role.  (I don't even want to do that; the DRY thing would be to simply append the one flag I need to configure_flags, but there's no syntax for that.)

So neither of the obvious (to me) ways to add a simple custom compiler flag to the standard nginx::source recipe works.

Before I wholesale copy the nginx cookbook into site-cookbooks and alter one line: what fundamental truth am I failing to discern here?  

Thanks in advance,

Roger