From 08f51a5975641879dd852988aa564352c769adc3 Mon Sep 17 00:00:00 2001
From: Genadi Samokovarov <gsamokovarov@gmail.com>
Date: Sat, 21 Feb 2015 16:11:35 +0200
Subject: [PATCH] Revamp unavailable session response message

When a user hit this message, it usually means two things:

1. The underlying server have been restarted.

2. The user runs in multi-process server and the request hit a worker,
   which doesn't store the session in memory.

I'm trying to hit the users here about the second case, since we
received yet another report of this happening and people getting
confused of why the console doesn't work.
---
 lib/web_console/middleware.rb       | 17 +++++++++++++----
 test/web_console/middleware_test.rb |  4 ++--
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/lib/web_console/middleware.rb b/lib/web_console/middleware.rb
index 3fc539fd..44b687fb 100644
--- a/lib/web_console/middleware.rb
+++ b/lib/web_console/middleware.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/string/strip'
+
 module WebConsole
   class Middleware
     TEMPLATES_PATH = File.expand_path('../templates', __FILE__)
@@ -7,6 +9,13 @@ class Middleware
       binding_change_re: %r{/repl_sessions/(?<id>.+?)/trace\z}
     }
 
+    UNAVAILABLE_SESSION_MESSAGE = <<-END.strip_heredoc
+      Session %{id} is is no longer available in memory.
+
+      If you happen to run on a multi-process server (like Unicorn) the process
+      this request hit doesn't store %{id} in memory.
+    END
+
     cattr_accessor :whiny_requests
     @@whiny_requests = true
 
@@ -73,7 +82,7 @@ def id_for_repl_session_stack_frame_change(request)
 
       def update_repl_session(id, params)
         unless session = Session.find(id)
-          return respond_with_unavailable_session
+          return respond_with_unavailable_session(id)
         end
 
         status  = 200
@@ -85,7 +94,7 @@ def update_repl_session(id, params)
 
       def change_stack_trace(id, params)
         unless session = Session.find(id)
-          return respond_with_unavailable_session
+          return respond_with_unavailable_session(id)
         end
 
         session.switch_binding_to(params[:frame_id])
@@ -97,10 +106,10 @@ def change_stack_trace(id, params)
         Rack::Response.new(body, status, headers).finish
       end
 
-      def respond_with_unavailable_session
+      def respond_with_unavailable_session(id)
         status = 404
         headers = { 'Content-Type' => 'application/json; charset = utf-8' }
-        body    = { output: 'Unavailable session' }.to_json
+        body    = { output: format(UNAVAILABLE_SESSION_MESSAGE, id: id)}.to_json
 
         Rack::Response.new(body, status, headers).finish
       end
diff --git a/test/web_console/middleware_test.rb b/test/web_console/middleware_test.rb
index 422099b3..baf041f2 100644
--- a/test/web_console/middleware_test.rb
+++ b/test/web_console/middleware_test.rb
@@ -96,13 +96,13 @@ def call(env)
     test 'unavailable sessions respond to the user with a message' do
       xhr :put, '/repl_sessions/no_such_session', { input: '__LINE__' }
 
-      assert_equal({ output: 'Unavailable session' }.to_json, response.body)
+      assert_equal(404, response.status)
     end
 
     test 'unavailable sessions can occur on binding switch' do
       xhr :post, "/repl_sessions/no_such_session/trace", { frame_id: 1 }
 
-      assert_equal({ output: 'Unavailable session' }.to_json, response.body)
+      assert_equal(404, response.status)
     end
 
     private