Garner: Anatomy of a Ruby Gem

Originally presented on May 21, 2014 at the "Anatomy of a Gem" Meetup: http://www.meetup.com/Anatomy-of-a-Ruby-Gem/events/176176352/

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Transcript

1. GARNER ANATOMY OF A RUBY GEM
5. CACHE RULES EVERYTHING AROUND ME
6. WHY CACHE? 1. REDUCE REPETITIVE COMPUTATION
7. WHY CACHE? 2. SHIFT DATA ACCESS PATTERN
8. SHIFT
9. SHIFT From bottlenecked, disk-bound stores ...to in-memory stores
10. SHIFT From bottlenecked, disk-bound stores ...to distributed stores
11. PostgreSQL MySQL MongoDB Memcached Redis Memory Local File
12. But... WHY GARNER? Rails already has caching!
13. PAGE CACHING! class PostsController < ActionController::Base caches_page :show def show @post = Post.find(params[:id]) end end
14. ACTION CACHING! class PostsController < ActionController::Base caches_action :show before_filter :authenticate_user! def show @post = Post.find(params[:id]) end end
15. CLEAN. SIMPLE.
16. CLEAN. SIMPLE. Caching by design.
17. Caching by design. CLEAN. SIMPLE.
18. Caching that HAPPENS. AND THEN THERE’S...
22. Some people, when confronted with a problem, think “I know, I’ll add caching.”
23. FRAGMENT CACHING!!! -# app/views/posts/show.html.haml = cache [ "v1", @post ] do %h1 = @post.title %section = @post.body %section = render @post.comments
24. FRAGMENT CACHING!!! -# app/views/posts/index.html.haml - @posts.each do |post| = cache [ "v1", post ] do %section = @post.summary
27. -# app/views/posts/index.html.haml - @posts.each do |post| = cache [ "v1", post ] do %section = @post.summary -# app/views/posts/show.html.haml = cache [ "v1", @post ] do %h1 = @post.title %section = @post.body %section = render @post.comments
28. -# app/views/posts/index.html.haml - @posts.each do |post| = cache [ "v1", post ] do %section = @post.summary -# app/views/posts/show.html.haml = cache [ "v1", @post ] do %h1 = @post.title %section = @post.body %section = render @post.comments
29. There are only two hard things in Computer Science: cache invalidation and naming things. — Phil Karlton
31. Rails.cache.clear and wait until it happens again!
32. ENTER GARNER. Better ad-hoc caching.
33. ENTER GARNER. Framework-independent caching.
34. SINATRA RACK PADRINO GRAPE
35. ENTER GARNER. A readable, extensible caching library.
36. Inside GARNER Step 1: Identify key concepts.
37. Inside GARNER “Identity” The unique cache block.
38. “Identity” garner do # ... end
39. Inside GARNER “Binding” Any “live” changing model to which a cache result is tied.
40. “Binding” garner.bind(Artwork.find(params[:id])) do # ... end
41. “Binding” garner.bind(Artwork.identify(params[:id])) do # ... end
42. Inside GARNER “Key” Any static name-value pair used to identify a cache result.
43. “Key” garner.bind(@artwork).key(admin: is_admin?) do # ... end
44. “Key” garner.bind(Artwork.identify(params[:id])) do # ... end Rails.cache.fetch('???') do end
46. Inside GARNER “Context” A code location from which Garner is invoked (e.g., Rack/Grape request context)
47. “Context” get '/artwork/:id' garner.bind(Artwork.identify(params[:id])) do # One long operation... end garner.bind(Artwork.identify(params[:id])) do # Another long operation... Same binding! end end
48. “Context” artwork = garner.bind(Artwork.identify(params[:id]) do Artwork.find(params[:id]) end error!('Artwork Not Found', 404) unless artwork error!('Forbidden', 403) unless artwork.can_be?(:read, current_user) garner.bind(artwork).different_for(:partners) do if params[:format].to_s == "txt" error!('Artwork Image Not Found', 404) unless artwork.has_image? artwork.default_image.to_ascii elsif cdn_request? artwork.as_json(properties: :public) else artwork.as_json_for(current_user) end end
49. “Context” artwork = garner.bind(Artwork.identify(params[:id]) do Artwork.find(params[:id]) end error!('Artwork Not Found', 404) unless artwork error!('Forbidden', 403) unless artwork.can_be?(:read, current_user) garner.bind(artwork).different_for(:partners) do if params[:format].to_s == "txt" error!('Artwork Image Not Found', 404) unless artwork.has_image? artwork.default_image.to_ascii elsif cdn_request? artwork.as_json(properties: :public) else artwork.as_json_for(current_user) end end
50. “Context” artwork = garner.bind(Artwork.identify(params[:id]) do Artwork.find(params[:id]) end error!('Artwork Not Found', 404) unless artwork error!('Forbidden', 403) unless artwork.can_be?(:read, current_user) garner.bind(artwork).different_for(:partners) do if params[:format].to_s == "txt" error!('Artwork Image Not Found', 404) unless artwork.has_image? artwork.default_image.to_ascii elsif cdn_request? artwork.as_json(properties: :public) else artwork.as_json_for(current_user) end end
51. “Context” artwork = garner.bind(Artwork.identify(params[:id]) do Artwork.find(params[:id]) end error!('Artwork Not Found', 404) unless artwork error!('Forbidden', 403) unless artwork.can_be?(:read, current_user) garner.bind(artwork).different_for(:partners) do if params[:format].to_s == "txt" error!('Artwork Image Not Found', 404) unless artwork.has_image? artwork.default_image.to_ascii elsif cdn_request? artwork.as_json(properties: :public) else artwork.as_json_for(current_user) end end
52. Contexts... Caller Context
53. Contexts... Caller Context GET Request Context
54. Contexts... Caller Context GET Request Context POST Request Context
55. HOW DO WE COMPUTE UNIQUE KEYS FOR ALL THESE CONTEXTS?
56. STRATEGIES!
58. module Garner::Strategies::Context::Key class Base def self.apply(identity, ruby_context = nil) identity end end end Base Strategy
59. RequestGet Strategy module Garner::Strategies::Context::Key class RequestGet < Base def self.apply(identity, ruby_context = nil) return identity unless (ruby_context.respond_to?(:request)) request = ruby_context.request if request && ["GET", "HEAD"].include?(request.request_method) identity.key(field => request.GET.dup) end identity end end end
60. Jsonp Strategy module Garner::Strategies::Context::Key class Jsonp < Base def self.apply(identity, ruby_context = nil) key_hash = identity.key_hash return identity unless key_hash[field] key_hash[field].delete("callback") key_hash[field].delete("_") identity end end end
61. Caller Strategy module Garner::Strategies::Context::Key class Caller < Base def self.apply(identity, ruby_context = nil) value = nil if ruby_context.send(:caller) ruby_context.send(:caller).compact.each do |line| parts = line.match(/(?<filename>[^:]+)\:(?<lineno>[^:]+)/) file = (Pathname.new(parts[:filename]).realpath.to_s rescue nil) next if file.nil? || file == "" next if file.include?(File.join("lib", "garner")) if (root = Garner.config.caller_root) root += File::SEPARATOR unless root[-1] == File::SEPARATOR next unless file =~ /^#{root}/ value = "#{file.gsub(root || "", "")}:#{parts[:lineno]}" else value = "#{file}:#{parts[:lineno]}" end break end end value ? identity.key(field => value) : identity end end end
62. Strategies make Implementation easier!
63. Strategies make Implementation Configuration easier!
64. Configuration Garner.configure do |config| config.context_key_strategies = [ Garner::Strategies::Context::Key::Caller, Garner::Strategies::Context::Key::RequestGet, Garner::Strategies::Context::Key::RequestPost, Garner::Strategies::Context::Key::RequestPath, Garner::Strategies::Context::Key::TrackedGrapeHeaders, Garner::Strategies::Context::Key::Auth ] end
65. Strategies make Implementation Configuration Unit Testing easier!
66. Unit Testing describe Garner::Strategies::Context::Key::Caller do before(:each) do @cache_identity = Garner::Cache::Identity.new @mock_context = double("object") end subject { Garner::Strategies::Context::Key::Caller } it_behaves_like "Garner::Strategies::Context::Key strategy" it "ignores blank caller location" do @mock_context.stub(:caller) { [""] } subject.apply(@cache_identity, @mock_context) @cache_identity.key_hash[:caller].should be_nil end # ... end
67. Unit Testing describe Garner::Strategies::Context::Key::Caller do before(:each) do @cache_identity = Garner::Cache::Identity.new @mock_context = double("object") end subject { Garner::Strategies::Context::Key::Caller } it_behaves_like "Garner::Strategies::Context::Key strategy" it "ignores blank caller location" do @mock_context.stub(:caller) { [""] } subject.apply(@cache_identity, @mock_context) @cache_identity.key_hash[:caller].should be_nil end # ... end
68. Unit Testing describe Garner::Strategies::Context::Key::Caller do before(:each) do @cache_identity = Garner::Cache::Identity.new @mock_context = double("object") end subject { Garner::Strategies::Context::Key::Caller } it_behaves_like "Garner::Strategies::Context::Key strategy" it "ignores blank caller location" do @mock_context.stub(:caller) { [""] } subject.apply(@cache_identity, @mock_context) @cache_identity.key_hash[:caller].should be_nil end # ... end
69. Unit Testing describe Garner::Strategies::Context::Key::Caller do before(:each) do @cache_identity = Garner::Cache::Identity.new @mock_context = double("object") end subject { Garner::Strategies::Context::Key::Caller } it_behaves_like "Garner::Strategies::Context::Key strategy" it "ignores blank caller location" do @mock_context.stub(:caller) { [""] } subject.apply(@cache_identity, @mock_context) @cache_identity.key_hash[:caller].should be_nil end # ... end
70. Unit Testing describe Garner::Strategies::Context::Key::Caller do before(:each) do @cache_identity = Garner::Cache::Identity.new @mock_context = double("object") end subject { Garner::Strategies::Context::Key::Caller } it_behaves_like "Garner::Strategies::Context::Key strategy" it "ignores blank caller location" do @mock_context.stub(:caller) { [""] } subject.apply(@cache_identity, @mock_context) @cache_identity.key_hash[:caller].should be_nil end # ... end
71. Strategies make Implementation Configuration Unit Testing easier!
72. Where else can we use strategies? Binding Keys
73. Where else can we use strategies? Binding Keys Binding Invalidation
74. QUESTIONS???