Hi Joe,
This sounds really good! I've been working on EC2 on Rails (
http://ec2onrails.rubyforge.org/ ), which was mentioned previously in this
thread (thanks Paul M.), and I could really use this.
My project started out as just a public server image but I've recently added
Capistrano tasks (available as a gem) to configure it. I've got partially
working support for multiple images, there's a Capistrano task that sets the
role of each server and configures them to communicate with the others.
The main thing that I don't have yet though is managing the instance
lifecycle and firewall settings from Capistrano, and I'm really hoping take
advantage of somebody else's work since there seems to be lots going on in
that area (though I'm not sure which way to go because capsize seems to have
replaced capazon but it hasn't released any code yet and the website isn't
up.) Hopefully we can all combine forces to make EC2 a kick-ass Rails
platform.
There may also be some overlap with the roles stuff you've got on the go and
I'd happily use yours instead if it fit.
Paul
(To reach me off-list replace 'lists' in my email address with 'paul').
On 9/30/07, Joe <[EMAIL PROTECTED]> wrote:
>
>
> Hi all,
>
> I've been working on a plugin to manage deployments of clusters on EC2
> through Capistrano. I'm looking to see if anyone is interested in
> collaborating on it, or using it in alpha form to give me some
> feedback. I'm not going to release it yet since it needs more
> development and testing, but I would like to get some suggestions on
> features to add.
>
> The tool is meant to manage the setup and confiiguration of machines
> prior to running a normal cap:deploy of a specific application. It is
> not meant to replace that.
>
> Here's an example of a cluster recipe (this is made up, so there may
> be some logical errors in the setup, but it should illiustrate the
> idea):
>
> -----
>
> cluster = elasticize.creater_cluster("mykey") do
> on_create do |cluster|
> app_group = create_group(cluster, :app) do
> authorize_ingress :proto => :tcp, :ports => 22
> authorize_ingress :proto => [ :tcp, :udp ], :ports => 5036
> end
> webserver_group = create_group(cluster, :webserver_group) do
> authorize_ingress :proto => :tcp, :ports => [ 22, 80 ]
> end
>
> app_group.authorize_ingress :from => :webserver_group
> webserver_group.authorize_ingress :from => :app_group
> end
> end
>
> app = elasticize.create_image :app, 'ami-12345678',
> cluster, :app_group
> web = elasticize.create_image :web, 'ami-87654321',
> cluster, :webserver_group do
> on_create do
> # Get security updates
> run "aptitude update -y"
> run "aptitude upgrade -y"
> end
> end
>
> elasticize.create_role :postfix, web do
> on_create do |process|
> modify "/etc/postfix/main.cf" do |r|
> r.sub(/(^myhostname[^=]*=.*$)/, "myhostname =
> #{process.instance.dns}")
> end
> end
>
> on_stop { run "/etc/init.d/postfix stop" }
> on_start do |process|
> run "/etc/init.d/postfix start"
> process.notify! :app, :port => 1234
> end
> end
>
> elasticize.create_role :app, rails do
> needs :db, :primary => true
> needs :postfix
>
> on_receive do |process, source, event, *rest|
> if event == :on_start
> case source.role.name.to_sym
> when :db
> ip = process.instance.private_dns
> port = *rest
> when :postfix
> # TODO: modify the rails configuration to point to the postfix
> server
> ip = process.instance.private_dns
> port = *rest
> end
> end
> end
> end
>
> # Create an elastic role for the web server, bound to the 'rails' AMI
> elasticize.create_role :web, rails do
> needs :app
>
> on_receive do |process, source, event, *rest|
> if event == :on_start
> case source.role.name.to_sym
> when :app
> end
> end
> end
>
> on_create do
> # Install needed gems
> install_gem "daemons"
> install_gem "gem_plugin"
> install_gem "mongrel_cluster"
> install_gem "mongrel", :version => '1.0.1'
> end
> end
>
> -----
>
> You can then create the cluster with a cap cluster:create. This will
> create the keys, security groups, permissions and instances. When a
> particular instance is created, its corresponding image's 'on_start'
> callback is called. Additionally, the create task will bind all
> 'elasitc' roles to a particular machine and create the appropriate
> capistrano role internally. When the binding occurs, the corresponding
> on_start callback are called for the process' corresponding role.
> There are additional callbacks when instances are terminated or leave
> the cluster.
>
> The 'needs' method indicates that a particular elastic role is
> dependent upon another, and that its' processes will accept
> notifications (in the on_receive handler) of specific events within
> the cluster from prerequisite processes (where a process represents a
> binding of a role to an EC2 instance, since a role can have multiple
> processes). The notifications are specified via the notify! method in
> a process' on_start callback, and allows that process to deliver
> dynamic configuration data to its dependent roles' processes.
>
> The 'provides' method specifies the number of processes which will
> exist for a given role. Also, 'create_role' can specify capistrano
> subroles (limited to a hash of keys to boolean values for now) like
> this:
>
> primary = elasticize.create_role :db, some_image, :primary => true do
> # Default is one if unspecified
> provides :exactly => 1
> end
>
> secondary = elasticize.create_role, :db, some_image do
> provides :min => 2, :max => 4
> end
>
> A planned feature will allow you to add and remove processes
> dynamically, bounded by the min / max number specified in the recipe.
>
> cap cluster:add ROLE=db
>
> This is not meant to be a thorough write up, just a taste if what is
> available.
>
> If you think you may be able to help, or just have some ideas for what
> you'd like to see, please get in touch. In particular, API feedback or
> help writing tests would be greatly appreciated.
>
> Joe
>
>
> >
>
--
http://pauldowman.com
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