Added Actor#tail method that makes it easy to create cross-server tails [DHH]

git-svn-id: http://svn.rubyonrails.org/rails/tools/capistrano@4162 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

CHANGELOG

@@ -1,5 +1,12 @@
 *SVN*
 
+* Added Actor#tail method that makes it easy to create cross-server tails [DHH]. Example:
+
+    desc "Run a tail on multiple log files at the same time"
+    task :tail_fcgi, :roles => :app do
+      tail "#{shared_path}/log/fastcgi.crash.log"
+    end
+
 * Make update_code and symlink a macro task under the name "update" for easy of deploy to servers that does not run fcgis [DHH]
 
 * Changed setup, update_code, rollback_code, and symlink to work on all servers instead of only those in the :app, :web, and :db roles. A server can opt out of being part of the release deployment by setting :no_release => true [DHH]

lib/capistrano/actor.rb

@@ -212,6 +212,27 @@ module Capistrano
       end
     end
 
+    # Puts a tail on the file from all servers that are the target of the
+    # current task. All the tails will be joined into a single coherent stream,
+    # so you can watch 10 log files as though they were one. Do note that this
+    # is quite expensive from a bandwidth perspective, so use it with care.
+    #
+    # Example:
+    #
+    #   desc "Run a tail on multiple log files at the same time"
+    #   task :tail_fcgi, :roles => :app do
+    #     tail "#{shared_path}/log/fastcgi.crash.log"
+    #   end
+    def tail(file)
+      run "tail -f #{file}" do |ch, stream, out|
+        puts out if stream == :out
+        if stream == :err
+          puts "[err : #{ch[:host]}] #{out}"
+          break
+        end
+      end
+    end
+
     # Deletes the given file from all servers targetted by the current task.
     # If <tt>:recursive => true</tt> is specified, it may be used to remove
     # directories.