First pass for router v2 implementation. The init version of router v…

…2 is done by

Jun Xiao, polished by Anfernee with a couple of bug fixes and enhancement.

router v2 decouples control and data path to some extent, it's a logic router
including both nginx and uls (upstream location server) parts.

uls (aka control plane) is based on legacy router:
- all communications with nats are kept the same as before
- client facing interface (actually connected to nginx) is simplified to
  handle the location query/stats update from nginx only.
- the original app facing interface is totally removed.

nginx (aka data plane)
- package lua in nginx so most functionalities can be implemented with it.
- for each request, nginx will generate a subrequest (to fit in nginx
  single thread event model) which carries location query/stats info to uls,
  the response of the subrequest will return backend addr and also an
  opaque tags (only known by uls), and the corresponding main request will
  also be awaked and routed to the backend server, when a response from backend
  is returned back, the counter associated with the particular opaque tags
  will be incremented accoring to the response code. The next incoming
  request will always help to carry not-synced stats to uls along with
  its location query.
- sticky session and trace header are also implemented here,
  also their key related config are moved to nginx part.

testing
- "rake spec" will only test uls, while "rake test" will run both unit test and
  integration test with nginx
- integration test requires nginx with lua module installed running

Change-Id: I9b25b24c449b0421754e541ab5ba60a00c551da9

Rakefile

@@ -49,7 +49,11 @@ namespace "test" do
     sh("cd spec && rake spec")
   end
 
- task "spec:rcov" do |t|
+  task "test" do |t|
+    sh("cd spec && rake test")
+  end
+
+  task "spec:rcov" do |t|
     sh("cd spec && rake spec:rcov")
   end
 end

lib/router.rb

@@ -21,7 +21,6 @@
 
 require 'router/const'
 require 'router/router'
-require 'router/app_connection'
 require 'router/client_connection'
 require 'router/utils'
 
@@ -183,4 +182,3 @@
   end
 
 end
-