No need to modify rack env. Remove min_percent setting, just use 0.01.

lib/rack/profiler.rb

@@ -11,48 +11,42 @@ def initialize(app)
     end
 
     def call(env)
-      if profiling?(env)
-        profile(env)
+      if mode = profiling?(env)
+        profile(env, mode)
       else
         @app.call(env)
       end
     end
 
     private
-      def profile(env)
-        RubyProf.measure_mode = RubyProf.const_get(env['rack.profiler.measure_mode'].upcase)
+      def profile(env, mode)
+        RubyProf.measure_mode = RubyProf.const_get(mode.upcase)
         result = RubyProf.profile { @app.call(env) }
-        [200, calltree_headers(env), calltree_body(env, result)]
+        [200, calltree_headers(env, mode), calltree_body(env, result)]
       end
 
       def profiling?(env)
-        if RubyProf.running?
-          false
-        else
+        unless RubyProf.running?
           request = Rack::Request.new(env)
           if mode = request.params.delete('profile')
             if MODES.include?(mode)
-              env['rack.profiler.measure_mode'] = mode
-              env['rack.profiler.min_precent'] = (request.params.delete('min_percent') || 0.01).to_f
-              true
+              mode
             else
               env['rack.errors'] << "Invalid RubyProf measure_mode: #{mode}. Use one of #{MODES.to_a.join(', ')}"
               false
             end
-          else
-            false
           end
         end
       end
 
-      def calltree_headers(env)
+      def calltree_headers(env, mode)
         { 'Content-Type' => 'application/octet-stream',
-          'Content-Disposition' => %(attachment; filename="#{::File.basename(env['PATH_INFO'])}.#{env['rack.profiler.measure_mode']}.tree") }
+          'Content-Disposition' => %(attachment; filename="#{::File.basename(env['PATH_INFO'])}.#{mode}.tree") }
       end
 
       def calltree_body(env, result)
         body = StringIO.new
-        RubyProf::CallTreePrinter.new(result).print(body, :min_percent => env['rack.profiler.min_percent'])
+        RubyProf::CallTreePrinter.new(result).print(body, :min_percent => 0.01)
         body.rewind
         body
       end