Just to clarify: it _is_ legal to _declare_ a task for a non-existant
or empty role. It just currently raises an exception when you try to
execute that task, if no servers exist in that role at the time.
As for why that is the case, I suppose it's because I couldn't
envision a use case for a task with empty roles, and figured that
more often than not it would indicate a typo on the user's part. (The
current behavior has actually caught errors in my recipe files
several times.) You've raised an interesting point, but I wonder if
you could solve it without resorting to hacking Capistrano. Could you
just add a check at the beginning of those tasks, which just exited
the task if there were no matching tasks?
task :something, :roles => %(this that) do
next if find_servers_for_task(current_task).empty?
# ...
end
If that becomes a particularly useful idiom, it could maybe be added
to Capistrano directly, via an option to tasks, something like this:
task :something, :roles => %(this that), :if_no_servers_match
=> :skip do
# ...
end
- Jamis
On Jun 5, 2007, at 4:36 PM, Mathieu wrote:
>
> Hello,
>
> We are currently using CfEngine to deploy our complex application
> (complex because a lot of different components to be installed and
> configured according to one or more roles for each host). I ran into
> so many problems with CfEngine (it might be a good tool, but it is
> definitely not the tool for our needs). I would like to replace it
> with Capistrano.
>
> I am using Capistrano (1.99.1) to deploy a complex application on a
> set of hosts. Deploying the application means installing RPM and GEM
> packages, customized configuration (generated previously, customized
> according to hosts roles), and creating several directories, crontab
> entries, etc...
>
> I wrote a set of tasks for deploying each set of components
> (installing dependencies, application components, configuration
> files, system configuration, etc...). Each task handles one or more
> roles. All that is pretty standard I think.
>
> I started facing a problem when I tried to associate tasks with roles
> that are not necessarily declared. Capistrano raises an error when
> declaring a task for a role that is not declared or when declaring an
> empty role.
>
> Our application is installed of a platform which size may greatly
> differ. We can build a test platform on one single host for instance,
> or on twenty hosts for a production platform. Some roles that run
> statistic servers, SIP registrar, etc... are mandatory. Because the
> combinations are numerous, I wanted to handle them in a simple way: a
> task linked to a role is executed if at least one host belongs to
> this role, if not it is just discarded.
>
> I am currently patching the Capistrano instance to be able to handle
> this case:
>
> def instanciate_capistrano
> cap = Capistrano::Configuration.new
> cap.logger.level = Capistrano::Logger::INFO
> cap.set(:password) { Capistrano::CLI.password_prompt }
> cap.load(File.dirname(__FILE__) + "/../lib/recipes.rb")
>
> # patch role_list_from to allow empty roles
> cap.instance_eval do
> alias orig_role_list_from role_list_from
> def role_list_from(roles)
> roles = roles.split(/,/) if String === roles
> Array(roles).map do |role|
> role = String === role ? role.strip.to_sym : role
> role
> end
> end
>
> alias orig_execute_task execute_task
> def execute_task(task)
> orig_execute_task(task) unless find_servers_for_task
> (task).empty?
> end
>
> end
> return cap
> end
>
> I was wondering if some of you guys had already faced the same
> problem, and how you did handle it. Why isn't it allowed to declare a
> task for a role that doesn't exist?
>
> Thanks!
>
> Mathieu
>
>
>
> >
--~--~---------~--~----~------------~-------~--~----~
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at http://groups.google.com/group/capistrano
-~----------~----~----~----~------~----~------~--~---
