Stuck in the Middle: Leverage the power of Rack::Middleware

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Stuck in the Middle Leverage the power of Rack::Middleware

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§  What? §  How? §  Why? §  Who…?

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What?

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Rack

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Your Application

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CGI

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http://www.whynot.io/ruby/what-is-rack-in-ruby/

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Rack ¤ Incoming Request: ¤ the “environment” hash ¤ Outgoing Response: ¤ Status code ¤ Headers ¤ Content body

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Rack

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Rack::Middleware

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http://www.whynot.io/ruby/what-is-rack-in- ruby/

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Handler

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Handler Adapter

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Handler Adapter Middlewares

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Middleware in Rails q  ActionDispatch::Static q  Rails::Rack::Logger q  ActionDispatch::Cookies q  ActionDispatch::Flash q  ActionDispatch::ParamsParser

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How?

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A very basic Middleware Ping!

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# lib/middleware/ping.rb

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# lib/middleware/ping.rb class Ping end

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# lib/middleware/ping.rb module Middleware class Ping end end

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# Middleware::Ping def initialize(app) @app = app end

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# Middleware::Ping def initialize(app) @app = app end def call(env) end

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# Middleware::Ping def initialize(app) @app = app end def call(env) [‘200’, {}, [“Pong!”]] end

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# Middleware::Ping def call(env) request = Rack::Request.new(env) [‘200’, {}, [“Pong!”]] end

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{ "PATH_INFO" => "/ping.json", "QUERY_STRING" => "", "REQUEST_METHOD" => "GET", "REQUEST_URI" => "http://localhost:3000/ping.json", "REQUEST_PATH" => "/ping.json" ... }

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# Middleware::Ping def call(env) request = Rack::Request.new(env) return @app.call(env) unless request.path == ‘/ping’ [‘200’, {}, [“Pong!”]] end

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A less basic middleware Request response time logging

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# lib/middleware/request_time_logging.rb module Middleware class RequestTimeLogging end end

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# Middleware::RequestTimeLogging def initialize(app) @app = app end

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# Middleware::RequestTimeLogging def call(env) end

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# Middleware::RequestTimeLogging def call(env) @app.call(env) end

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# Middleware::RequestTimeLogging def call(env) start = Time.now @app.call(env) end

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# Middleware::RequestTimeLogging def call(env) start = Time.now @app.call(env) elapsed = Time.now - start end

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# Middleware::RequestTimeLogging def call(env) start = Time.now @app.call(env) elapsed = Time.now - start [status, headers, response] end

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# Middleware::RequestTimeLogging def call(env) start = Time.now @app.call(env) elapsed = Time.now - start [status, headers, response] end

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# Middleware::RequestTimeLogging def call(env) start = Time.now status, headers, response = @app.call(env) elapsed = Time.now - start [status, headers, response] end

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# Middleware::RequestTimeLogging def call(env) start = Time.now status, headers, response = @app.call(env) elapsed = Time.now - start [status, headers, response] end

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# Middleware::RequestTimeLogging def call(env) start = Time.now status, headers, response = @app.call(env) elapsed = Time.now - start log_response_time( elapsed ) [status, headers, response] end

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# Middleware::RequestTimeLogging def call(env) start = Time.now status, headers, response = @app.call(env) elapsed = Time.now - start request = Rack::Request.new(env) log_response_time( elapsed, request ) [status, headers, response] end

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# Middleware::RequestTimeLogging private def log_response_time(elapsed_time, request) end

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# Middleware::RequestTimeLogging private def log_response_time(elapsed_time, request) end

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# Middleware::RequestTimeLogging def log_response_time(elapsed_time, request) end

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# Middleware::RequestTimeLogging def log_response_time(elapsed_time, request) { response_time_secs: elapsed_time, path: request.path } end

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# Middleware::RequestTimeLogging def log_response_time(elapsed_time, request) payload = { response_time_secs: elapsed_time, path: request.path } SplunkLogger.log(‘request.response_time’, payload) end

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Throttling https://github.com/bendiken/rack-throttle

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lib/rack/throttle/limiter.rb

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lib/rack/throttle/limiter.rb

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lib/rack/throttle/limiter.rb

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Why?

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Middleware can simplify your application

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addons.heroku.com

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elements.heroku.com

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Middleware can protect your application

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Middleware sees both the request & response object

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Middleware can be a code sharing mechanism

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Who...? Things that will trigger your successors to `git blame` your code

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Order

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> rake middleware

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Order use Rack::Sendfile use ActionDispatch::Static … run MyApp::Application.routes

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Order use Rack::Sendfile use ActionDispatch::Static … use ActionDispatch::RequestId use Rails::Rack::Logger … run MyApp::Application.routes

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Order use ActionDispatch::RequestId use Rails::Rack::Logger … use Rack::Sendfile use ActionDispatch::Static run MyApp::Application.routes

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Order use OmniAuth::Builder use Warden::Manager use WardenOmniAuth … use ActionDispatch::Session::ActiveRecordStore … run MyApp::Application.routes

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github.com/hassox/warden/wiki/Setup

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Order use ActionDispatch::Session::ActiveRecordStore … use OmniAuth::Builder use Warden::Manager use WardenOmniAuth … run MyApp::Application.routes

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Application Logic

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Application Logic

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Some Red Flags §  Modifying the request §  Awareness of business logic §  Awareness of models

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Mitigation Strategies §  Use app/middlewares §  Use app/hacks or lib/hacks §  Keyword comments

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Always return a response

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Thread Safety (if you set instance variables)

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# Middleware::Ping def initialize(app) @app = app end def call(env) [‘200’, {}, [“Pong!”]] end

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# Middleware::Ping def call(env) dup._call(env) end private def _call(env) [‘200’, {}, [“Pong!”]] end

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# Middleware::Ping def call(env) dup._call(env) end private def _call(env) [‘200’, {}, [“Pong!”]] end