Working on a way to use Capistrano to deploy to ec2. I know about
Capsize, but decided that I didn't want to hardcode image and instance
IDs anywhere -- particularly as Capistrano itself will eventually be
creating those itself.
The first roadblock was: I can use variables-as-blocks to define
things like the list of current instances, the latest instance, etc.
(Variables, not functions or tasks, because I figure that information
isn't going to change over the course of a single invocation of cap,
unless I change it myself.)
But I cannot define roles-as-blocks, and I want to find roles out from
the results of ec2-describe-instances (and probably other things as
well). So, I needed dynamic roles.
I'm completely new to the Rails and Capistrano community, so I'm not
sure what style conventions I should use, where to send patches, etc.
Here's the hack I have so far:
Capistrano::Configuration::Roles.module_eval do
alias_method :orig_role, :role
def role(which, *args, &block)
if !block_given? && args.empty? || block_given? && !args.empty?
raise ArgumentError, "you must specify exactly one of
either a
value or a block"
end
if block_given? then
which = which.to_sym
@roles[which] = block
else
# I apologize for this one-liner
orig_role(which, args.map{|item| String === item ?
Capistrano::ServerDefinition.new(item) : item})
end
end
end
Capistrano::Configuration::Servers.module_eval do
alias_method :find_servers_orig, :find_servers
def find_servers(options={})
hosts = server_list_from(ENV['HOSTS'] || options[:hosts])
if hosts.any?
hosts.uniq
else
roles = role_list_from(ENV['ROLES'] || options[:roles]
||
self.roles.keys)
roles.each { |role|
target = self.roles[role]
if target.respond_to?(:call)
self.roles[role] = target.call.map {
|server|
String === server ?
ServerDefinition.new(server, {}) : server
}
end
}
find_servers_orig(options)
end
end
end
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