是的。 Capistrano本机管理多台服务器。不需要capistrano ext。

您只需定义多个 roles

 角色：app，myserver.example.com
 role：db，mysecondserver.example。 com
 

默认情况下，您的任务将在每个服务器上执行。但是您可以将任务限制在一个或几个服务器上。

  task：migrate，：roles => [：app，：db] do 
＃... 
 end 
 

在这里，任务只能在应用程序和db角色上执行。

可以使用run方法执行相同操作。

 运行rake db：migrate，：roles => ：db 
 

rake db：migrate只能在数据库服务器上运行。

I'm currently setting up a new production environment for a Rails application which includes multiple, load-balanced application servers (currently only two, but this will increase over time).

I'd like to handle deployment of the app to all these servers in a single command using Capistrano (which I already use for my existing, single server). The only way I can see of doing this is to use capistrano-ext (which I actually already use to deploy to my test and staging environments), by defining a new 'environment' for each application server (app1, app2 and so on) and performing a deployment using something like:

cap app1 app2 app3 deploy

Is this the recommended way of doing it or is there a better approach?

Yeah. Capistrano manages multiple servers natively. No need for capistrano ext.
You only need to define multiple roles

role :app, "myserver.example.com"
role :db,  "mysecondserver.example.com"

By default your tasks will be executed on every server. But you can limit a task to one or some servers only.

task :migrate, :roles => [:app, :db] do
    # ...
end

Here, the task will be executed only on the app and db roles.

You can do the same with the run method.

run "rake db:migrate", :roles => :db

The rake db:migrate will be run only on the db server.