Identify current host

[Gary Richardson]

Hey,

Two part question that I haven't been able to answer:

1) can I get the current host a task is executing on? I've read some stuff about $CAPISTRANO:HOST$, but it doesn't seem to work for me

2) if I have an array of values (let's say an array that maps ec2 host names to ec2 instance id's), can I use this same method to look up something from that array?

For example:

task :example do

  instanceId = lookUpTable[hostname]

  run "somecommand -h #{hostname} -i #{instanceid}"

done

PS, the error I get when I run a task with $CAPISTRANO:HOST$ is:

  * executing "echo $CAPISTRANO:HOST$"

/usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/server_definition.rb:16:in `initialize': undefined method `match' for 101:Fixnum (NoMethodError)

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:80:in `new'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:80:in `wrap_server'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:98:in `wrap_list'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:97:in `map'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:97:in `wrap_list'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:59:in `to_ary'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:74:in `concat'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/role.rb:74:in `dynamic_servers'

         ... 28 levels...

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/lib/capistrano/cli/execute.rb:14:in `execute'

        from /usr/lib/ruby/gems/1.8/gems/capistrano-2.5.5/bin/cap:4

        from /usr/bin/cap:16:in `load'

        from /usr/bin/cap:16

Thanks!

[Rafael G.]

Gary Richardson wrote:
> Hey,
>
> Two part question that I haven't been able to answer:
>
> 1) can I get the current host a task is executing on? I've read some
> stuff about $CAPISTRANO:HOST$, but it doesn't seem to work for me

I tested this task and works for me:

task :host_name do
run "host $CAPISTRANO:HOST$"
end

What OS are you using? Could you paste your deploy.rb in
someplace(gist.github, pastie,...)?

> 2) if I have an array of values (let's say an array that maps ec2 host
> names to ec2 instance id's), can I use this same method to look up
> something from that array?

Capistrano uses ruby If you can do it with ruby you can do the same in a
capistrano task.

--
Rafa

[Gary Richardson]

Hmm. That's odd..$CAPISTRANO:HOST$ wasn't working for me on Friday. Must be them gremlins.

Is there another variable I can use to get the current host in the ruby code? This is what I'm trying to do:

  task :bootstrap, :roles => [:master] do

        # instanceids is an array containing hostname => instanceid

id = instanceids["$CAPISTRANO:HOST$"]

run "register_host -H $CAPISTRANO:HOST$ -s #{id}"

  end

Obviously, $CAPISTRANO:HOST$ doesn't interpolate on the id = instanceids[] line.

Thanks!

[Jamis Buck]

On Mon, Jul 6, 2009 at 9:06 AM, Gary
Richardson<gary.ri...@gmail.com> wrote:
> Hmm. That's odd..$CAPISTRANO:HOST$ wasn't working for me on Friday. Must be
> them gremlins.
> Is there another variable I can use to get the current host in the ruby
> code? This is what I'm trying to do:

Short answer: no.

Longer answer: yes, kind of.

Keep in mind one key concept: capistrano does not run a command on
each server sequentially; it runs the commands on all servers in
parallel. Thus, within a task, there is no such thing as a "current
host". What you have is a set of servers that match the current task,
and all commands invoked within that task will run in parallel on that
set of servers.

So, what you can do is get the list of matching servers:

task :bootstrap, :roles => :master do

servers = find_servers_for_task(current_task)
servers.each do |server|
puts "host: #{server.host}"
end
end

- Jamis

[Rafael G.]

Jamis Buck reply sometimes ago to this question:

http://groups.google.com/group/capistrano/browse_thread/thread/a83de628bcd73752/89b55c5b74177554?lnk=gst&q=[Capistrano]+Which+server+is+this+task+being+executed+on%3F#89b55c5b74177554

--
Rafa

[Rafael G.]

Sorry, I didn't saw your reply :-)

--
Rafa

[Gary Richardson]

Ok, I'm moving along here. This is what I've come up with:

task :host_name do

  servers = find_servers_for_task(current_task)

  servers.each do |server|

set :myServer, server.host

set :myId, instanceids[myServer]

real_host_name(:hosts => [myServer])

  end

end

task :real_host_name do

  run "echo #{myServer} - #{myId}"

end

The problem is that "real_host_name(:hosts => [myServer])" doesn't do what I expect it to :( -- real_host_name ends up getting called for all hosts in the current role.

Is there a way to change :hosts/:roles for a sub-task? Or possible call run with a limited subset of hosts?

Is there a better way of doing this?

Thanks!