1 files changed, 35 insertions, 0 deletions
diff --git a/railties/lib/rails/rack/log_tailer.rb b/railties/lib/rails/rack/log_tailer.rb
new file mode 100644
index 0000000000..a237cee6bc
--- /dev/null
+++ b/railties/lib/rails/rack/log_tailer.rb
@@ -0,0 +1,35 @@
+module Rails
+  module Rack
+    class LogTailer
+      EnvironmentLog = "#{File.expand_path(Rails.root)}/log/#{Rails.env}.log"
+
+      def initialize(app, log = nil)
+        @app = app
+
+        path = Pathname.new(log || EnvironmentLog).cleanpath
+        @cursor = ::File.size(path)
+        @last_checked = Time.now.to_f
+
+        @file = ::File.open(path, 'r')
+      end
+
+      def call(env)
+        response = @app.call(env)
+        tail_log
+        response
+      end
+
+      def tail_log
+        @file.seek @cursor
+
+        mod = @file.mtime.to_f
+        if mod > @last_checked
+          contents = @file.read
+          @last_checked = mod
+          @cursor += contents.size
+          $stdout.print contents
+        end
+      end
+    end
+  end
+end