Sinatra and JSONQuery Web Service

Sinatra, Testing in Sinatra, Redis Vassilis Vatikiotis, Athens Ruby Meetup 7

Sinatra  Web micro framework and DSL.  > 4000 LOC, 6 Classes. Study!  Modular & standalone style.  Small apps & web services.  Rack compatible.  Extendible.  Very popular: 182 gems in rubygems.org  MRI & 1.9, Rubinius 1.2.3, Jruby 1.6 full support.  MacRuby, IronRuby (reported OK).

Hello world require 'sinatra' get '/' do 'Hello world!' end Can't beat that!

Sinatra basics (1.2.6)  Route matching: HTTP method + URL pattern.  Strings, regexps. Conditions allowed. get '/say/:what/to/*', :host_name => /^admin./ do params[:what] what = #{what} params[:splat] # => Array erb :index end  Views and Templates.  ERB, Haml, Builder, Nokogiri, Sass, Markdown, Coffescript and more.  Embedded, inline, file.

Sinatra basics  Filters  Before and after filters.  URL patterns and conditions (just like routes).  Helpers support a host of tools:  Sessions.  Request “flow” control: halt, pass, trigger route.  Set HTTP headers, status, body, mime type.  .configure to set things to run once.  Examine request, logging.  Error handlers look like routes.

Sinatra – scope/binding  Everything inherits from Sinatra::Base  Request object accessible within route blocks, helper methods, filters, views, own methods.  Single application class for all requests; you cannot access request or session at class level.  Application scope accessible within:  settings.get within request scope.  class body & block to helper method.  blocks/procs used as value in set  block to Sinatra.new

Sinatra and Rack stack  Sits on top of Rack.  middleware pipelines via Sinatra::Base.use  Modular and Classic style.  Classic Sinatra::Application pollutes global namespace.  Modular Sinatra::Base we can build a stack e.g. more sinatra, padrino, ramaze, rails, any rack abiding citizen  We can dynamically create a Sinatra app... + (Object) Sinatra.new(base = Base, options = {}, &block)  ...and use it somewhere in the stack! use Sinatra { get('/') { ... } } run My::EndPoint

Shamelessly ripped example require 'sinatra/base' class LoginScreen < Sinatra::Base enable :sessions set :session_secret, 'super secret' get('/login') { haml :login } post('/login') do if params[:name] == 'admin' && params[:password] == 'admin' session['user_name'] = params[:name] else redirect '/login' end end end class MyApp < Sinatra::Base use LoginScreen before do unless session['user_name'] halt "Access denied, please <a href='/login'>login</a>." end end get('/') { "Hello #{session['user_name']}." } end

Extending Sinatra  Instance context: using helpers method module Sinatra module HTMLEscapeHelper def h(text) Rack::Utils.escape_html(text) end end helpers HTMLEscapeHelper end  Class context: using register method module Sinatra module LinkBlocker def block_links_from(host) before { halt 403, "Go Away!" if request.referer.match(host) } end end register LinkBlocker end

Testing in Sinatra  Use generic test frameworks – mix in Rack::Test::Methods. require 'rack/test' Check source!  Webrat / Capybara require minimal wiring.  Use last_response object, query everything you want. it "says hello" do get '/hello' response = JSON.parse(last_response.body) response["ProxyResponse"].should == @page_id last_response.should be_ok end it "says hello" do visit '/hello' page.should have_content('hello_world') end

Sinatra & testing  Sinatra is excellent for implementing web services.  Lean framework.  Views? I don't need views.  Rack middleware in place.  Sinatra/WS is excellent for getting comfy with testing.  Integration testing is easy; exercise and verify!  You are doing state verification.  Don't get confused with behavior verification (Rspec?)  Want to grok testing? Code a Sinatra web service.

Intermission I Bite the bullet: Test it!  Beginnings are hard! Grok testing, figure out the api(s), figure out which api(s), figure out when... go figure!  Test cycle: setup, exercise, verify, teardown.  Exercise SUT, use doubles for collaboration.  Test Double is a generic term for a test obj.  A stub provides a canned answer.  A mock “is a stub” which enforces behavior checks.  Classic TDD vs Mockist TDD vs BDD.

Intermission II Stub example Project.stub(:find).and_return( Project.new( :name => “Greek reboot”)) stub_project = Project.find(1) previous_count = manager.projects.count manager.projects << stub_project manager.projects.count.should == previous_count + 1  SUT is the manager object.  A stub is a collaborator used to help testing the SUT.

Intermission III Mock example post '/manager/:role' do manager.switch_role params[:role] end class Manager attr_accessor :role def switch_role( role ) @role = (role == 'team leader' ? 'project leader' : 'team leader') end end #this is my test it “/manager/role spews back the role” do mock_manager = Manager.new( :role => 'team leader' ) mock_manager.should_receive(:switch_role).and_return('project leader') post '/manager/:role', mock_manager last_response.body.should == 'project leader' end

Steps  Sinatra and HTTP services is ideal for getting you started with testing.  Write a small sinatra app, no views, think in term of HTTP endpoints.  REST is not required!  Integration test it. Minimal api knowledge. Want to try stubs? stub a :find user maybe?  Now do it backwards. Write tests first!  I'm severely TDDing!

JSON Query HTTP Service Goal  Service provides data in json format.  I need a portion of a map.  I need just a portion of a big data chunk.  I want to be able to query for my bits of data.  Ideally I want the data service to provide me with such a facility.  JSON Query Service deals with the above.

JSON Query HTTP Service Issues  JSON selector as a service.  JSONSelect, JSONPath, XPATH.  Issue: there is no established json selector mechanism.  Work around it or use non established methods,  own implementation.  Need to fetch and cache the requested source.  Issue: cache component need to scale out and be consistent.  Issue: potentially massive service load.

JSON Query HTTP Service Frontend  Sinatra.  No RESTful API. Do not need one (atm).  Request a portion of a json page.  Response is the requested json portion, with metadata. All wrapped in a json response.  Works for multiple URLs.

JSON Query HTTP Service Backend  Redis. keyvalue data store, can be used as cache.  Fast! compared with memcached? YMMV.  Clustering? Not here yet!  Used it as a concept. Selling point? Virtual Memory  What if we run out of memory?  suitable for large values, keys are requested URLs  Keys in memory, values on disk.  Idea: SSD for memory, slower disk for values.

How can I use it? require 'net/http' require 'json' post_data = { :apikey => "dc25ece96592813032f3605e95e8c6e9669cad46", :guid => "123123", :xpath => "//leg[2], //leg[1]", :url => "http://maps.googleapis.com/maps/api/directions/json? origin=Chicago,IL&destination=Los+Angeles,CA&waypoints=Joplin,MO| Oklahoma+City,OK&sensor=false” } document = Net::HTTP.post_form( URI.parse('http://jsonquery.heroku.com/v1/fetch_page') , post_data ) response = JSON.parse( document.body ) xpath_1 = response["ProxyResponse"]["url_1"]["xpath_1"][“response”] xpath_2 = response["ProxyResponse"]["url_1"]["xpath_2"][“response”]

Future  XML support.  Redis VM support is dropped in 2.4  Need to investigate memcache, membase, riak and so on. Many solutions according to domain.  Scale. How?  Usual approach so far is to spawn multiple processes.  Threaded vs Evented.  Unicorn, Mongrel, Thin, Rainbows, Passenger, Zbattery, Goliath.

Bibliography 1) Mocks aren't Stubs. Martin Fowler 2) Serviceoriented design with Ruby and Rails. Paul Dix et al 3) The Rspec book, David Chelimsky et al 4) Rails test prescriptions, Noel Rappin 5) Sinatra and testing from a pro: Peepcode PlaybyPlay (episode 54) with J. Barnette

Sinatra and JSONQuery Web Service

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