Extending Gems - Patterns and Anti-Patterns of Making Your Gem Pluggable

One strength of the Ruby community is the simplicity of sharing code via gems. When a gem is popular enough, it can even develop an ecosystem of additional gems that build on it.

But extending a gem that wasn't built with that flexibility in mind isn't always easy. This talk highlights tips and techniques for making your gem simpler to plug into, and avoid mistakes that will have devs cursing under their breath.

We'll cover the highs and lows of interacting with others gems, from configuration to documentation and everywhere in between.

http://rubyconf13.multifaceted.io/talks/extending-gems.html

Transcript

1. Extending Gems Patterns and Anti-Patterns of Making Your Gem Pluggable Jason Clark @jasonrclark Ruby Agent Engineer Monday, November 11, 13
2. 2 Storytime! Monday, November 11, 13
3. 3 newrelic_rpm module NewRelic::Agent::BrowserMonitoring def browser_monitoring_queue_time queue_time = current_transaction.queue_time millis = queue_time.to_f * 1000.0 clamp_to_positive(millis.round) end def footer_js_string(config) "... #{browser_monitoring_queue_time}" end end Monday, November 11, 13
4. 4 module NewRelic::Agent::BrowserMonitoring def current_timings TransactionTimings.new end def footer_js_string(config) "... #{current_timings.queue_time_in_millis}" end end newrelic_rpm Monday, November 11, 13
5. 5 Meanwhile... Elsewhere At New Relic http://flic.kr/p/9xEUug Monday, November 11, 13
6. 6 module NewRelic::Agent::BrowserMonitoring # MONKEY PATCHED! def footer_js_string(config) "... #{browser_monitoring_queue_time}" end end rpm_site Monday, November 11, 13
7. 7 http://pixabay.com/en/elephant-foot-ten-foot-elephant-52536/ Monday, November 11, 13
8. 8 Monday, November 11, 13
9. 9 Reskiq It forks then it threads! Monday, November 11, 13
10. 10 gem install my_awesome_code Monday, November 11, 13
11. Where We're Going 11 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
12. Pass It On 12 Monday, November 11, 13
13. Loggers 13 Monday, November 11, 13
14. activerecord 14 ActiveRecord::Base.logger = ::Logger.new("my_special.log") Monday, November 11, 13
15. 15 http://flic.kr/p/7GDRue Dependency Injection Monday, November 11, 13
16. 16 http://flic.kr/p/gzxjKu Duck Typing Monday, November 11, 13
17. Instrumentors 17 Monday, November 11, 13
18. excon 18 connection = Excon.new( 'http://nerd.jasonrclark.com', :instrumentor => SimpleInstrumentor ) Monday, November 11, 13
19. excon 19 class SimpleInstrumentor class << self attr_accessor :events def instrument(name, params = {}, &blk) puts "#{name} just happened." yield if block_given? end end end Monday, November 11, 13
20. 20 http://pixabay.com/en/elephant-foot-ten-foot-elephant-52536/ Monday, November 11, 13
21. Backends 21 Monday, November 11, 13
22. Delayed::Job 22 # without delayed_job @user.activate!(@device) # with delayed_job @user.delay.activate!(@device) Monday, November 11, 13
23. Delayed::Job 23 Monday, November 11, 13
24. Delayed::Job 24 ::Delayed.const_set(:Job, backend) Monday, November 11, 13
25. 25 newrelic_rpm def failed_jobs Delayed::Job.count( :conditions => 'failed_at is not NULL') end Monday, November 11, 13
26. Gem-Specific 26 Monday, November 11, 13
27. Resque 27 class SendMessageJob def self.perform(id, text) user = User.find(id) user.send_message(text) end end Resque.enqueue(SendMessageJob, 42, "Yo") Monday, November 11, 13
28. 28 Resque https://github.com/resque/resque/blob/master/docs/HOOKS.md class SendMessageJob def self.before_perform_log_it(*args) logger.debug("Messaging #{args}") end ... end Monday, November 11, 13
29. Where We've Been 29 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
30. Events 30 Monday, November 11, 13
31. What's Important? 31 Monday, November 11, 13
32. 32 Monday, November 11, 13
33. Surfacing Events 33 Monday, November 11, 13
34. 34 newrelic_rpm events = NewRelic::Agent.instance.events events.subscribe(:start_transaction) do set_transaction_custom_parameters end Monday, November 11, 13
35. 35 Resque Resque.after_fork do |job| ActiveRecord::Base.establish_connection end Monday, November 11, 13
36. 36 http://pixabay.com/en/elephant-foot-ten-foot-elephant-52536/ Monday, November 11, 13
37. Ordering? 37 Monday, November 11, 13
38. ActiveSupport::Notifications 38 activesupport Monday, November 11, 13
39. Where We've Been 39 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
40. Middleware 40 Monday, November 11, 13
41. 41 Rack::Cache ActionDispatch::Cookies YourApplication Web Request Monday, November 11, 13
42. 42 # [status, headers, response] def call(env) # ... before result = @app.call(env) # ... after result end Monday, November 11, 13
43. 43 # [status, headers, response] def call(env) # ... before result = @app.call(env) # ... after result end Monday, November 11, 13
44. http://flic.kr/p/SSGmF ActionDispatch::Static Rack::Lock <ActiveSupport::Cache::Strategy> Rack::Runtime Rack::MethodOverride ActionDispatch::RequestId Rails::Rack::Logger ActionDispatch::ShowExceptions ActionDispatch::DebugExceptions ActionDispatch::RemoteIp ActionDispatch::Reloader ActionDispatch::Callbacks ActiveRecord::ConnectionAdapters ActiveRecord::QueryCache ActionDispatch::Cookies ActionDispatch::Session::CookieStore ActionDispatch::Flash ActionDispatch::ParamsParser Rack::Head Rack::ConditionalGet Rack::ETag AgentSnoop::Middleware RpmTestApp::Application.routes Monday, November 11, 13
45. Who's There? 45 Monday, November 11, 13
46. 46 # [status, headers, response] def call(env) # ... before result = @app.call(env) # ... after result end Monday, November 11, 13
47. 47 class MyMiddleware def initialize(options=nil) # options == { :foo => 1 } end def call(worker, msg, queue) yield end end Monday, November 11, 13
48. 48 Sidekiq.configure_server do |config| config.server_middleware do |chain| chain.add MyMiddleware, :foo => 1 end end Monday, November 11, 13
49. Where We've Been 49 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
50. Lifecycle 50 Monday, November 11, 13
51. Forks and Daemons 51 http://flic.kr/p/79tE5Q Monday, November 11, 13
52. Forking 52 fork() state Monday, November 11, 13
53. fork() state fork() Forking 53 state Monday, November 11, 13
54. before_fork after_fork 54 Monday, November 11, 13
55. Add Threads 55 fork() Monday, November 11, 13
56. fork() Add Threads 56 Monday, November 11, 13
57. Enter the Lock 57 fork() @lock Monday, November 11, 13
58. @loick fork() Enter the Lock 58 @lock Monday, November 11, 13
59. 59 https://github.com/resque/resque/issues/1101 Forks + Threads + == Locks Resque Monday, November 11, 13
60. Load Up! 60 Monday, November 11, 13
61. unicorn 61 ♥ὑὑ~/myapp:unicorn_rails -c ./unicorn.rb unicorn_rails master unicorn_rails worker[0] unicorn_rails worker[1] unicorn_rails worker[2] unicorn_rails worker[3] Monday, November 11, 13
62. 62 loads gems forks after_fork starts loop forks after_fork starts loop loads gems preload_app true preload_app false unicorn Monday, November 11, 13
63. 63 loads gems forks after_fork starts loop forks after_fork starts loop loads gems preload_app true preload_app false unicorn Monday, November 11, 13
64. Where We've Been 64 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
65. Names and Paths 65 Monday, November 11, 13
66. Forced 66 Monday, November 11, 13
67. 67 Sequel.plugin :newrelic_instrumentation Monday, November 11, 13
68. 68 Sequel.plugin :newrelic_instrumentation => require 'sequel/plugins/newrelic_instrumentation' Monday, November 11, 13
69. 69 ~/source/newrelic/ruby_agent/lib: ls -la drwxr-xr-x Sep 19 14:46 . drwxr-xr-x Oct 10 11:19 .. drwxr-xr-x Oct 10 11:20 new_relic -rw-r--r-- Sep 19 14:46 newrelic_rpm.rb drwxr-xr-x Sep 19 14:46 sequel drwxr-xr-x Oct 7 08:53 tasks Monday, November 11, 13
70. 70 ~/source/newrelic/ruby_agent/lib: ls -la drwxr-xr-x Sep 19 14:46 . drwxr-xr-x Oct 10 11:19 .. drwxr-xr-x Oct 10 11:20 new_relic -rw-r--r-- Sep 19 14:46 newrelic_rpm.rb drwxr-xr-x Sep 19 14:46 sequel drwxr-xr-x Oct 7 08:53 tasks Monday, November 11, 13
71. 71 Sequel.plugin NewRelic::Sequel::Instrumentation Monday, November 11, 13
72. Generic 72 Monday, November 11, 13
73. 73 Monday, November 11, 13
74. 73 ActiveRecord Monday, November 11, 13
75. 73 ActiveRecord DataMapper Monday, November 11, 13
76. 73 ActiveRecord DataMapper HTTPClient Monday, November 11, 13
77. Qualify Yourself 74 Monday, November 11, 13
78. 75 newrelic_rpm module NewRelic module Agent class Thread < ::Thread ... end end end Monday, November 11, 13
79. elsewhere... 76 class Thread # Re-opened NewRelic::Agent::Thread # D'oh! end Monday, November 11, 13
80. 77 newrelic_plugin module NewRelic class Logger ... end end Monday, November 11, 13
81. 78 newrelic_rpm module NewRelic module Agent class AgentLogger LOG_LEVELS = { "debug" => Logger::DEBUG, ... } end end end Monday, November 11, 13
82. 79 newrelic_rpm module NewRelic module Agent class AgentLogger LOG_LEVELS = { "debug" => Logger::DEBUG, ... } end end end Monday, November 11, 13
83. 80 newrelic_rpm module NewRelic module Agent class AgentLogger LOG_LEVELS = { "debug" => ::Logger::DEBUG, ... } end end end Monday, November 11, 13
84. Where We've Been 81 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
85. Config 82 Monday, November 11, 13
86. yml 83 Monday, November 11, 13
87. yml + ERB 84 Monday, November 11, 13
88. yml + ERB 85 file = File.read("~/config/awesome_gem.yml") # Locals available in ERB default_awesome_key = "YEAH!" erb = ERB.new(file).result(binding) config = YAML.load(erb) Monday, November 11, 13
89. yml + ERB 86 ~/config/awesome_gem.yml development: name: <%= default_awesome_key %> license_key: <%= ENV["LICENSE_KEY"] %> Monday, November 11, 13
90. Ruby 87 Monday, November 11, 13
91. 88 unicorn worker_processes 5 preload_app true timeout 30 after_fork do |server, worker| defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection end Monday, November 11, 13
92. 89 on_worker_boot do ActiveSupport.on_load(:active_record) do ActiveRecord::Base.establish_connection end end Monday, November 11, 13
93. Great for Apps? What about Gems? 90 Monday, November 11, 13
94. 91 newrelic_rpm if defined?(::Puma) && ::Puma.respond_to?(:cli_config) config = ::Puma.cli_config config.options[:worker_boot] << Proc.new do NewRelic::Agent.after_fork(...) end end Monday, November 11, 13
95. 92 newrelic_rpm if defined?(::Puma) && ::Puma.respond_to?(:cli_config) config = ::Puma.cli_config config.options[:worker_boot] << Proc.new do NewRelic::Agent.after_fork(...) end end Monday, November 11, 13
96. Where We've Been 93 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
97. Docs 94 Monday, November 11, 13
98. README 95 Monday, November 11, 13
99. sinatra 96 Monday, November 11, 13
100. 97 Monday, November 11, 13
101. 98 Monday, November 11, 13
102. 99 Monday, November 11, 13
103. Expected Extensions? 100 Monday, November 11, 13
104. 101 Monday, November 11, 13
105. Don't Bury It 102 Monday, November 11, 13
106. 103 Monday, November 11, 13
107. 104 Monday, November 11, 13
108. Versioning 105 Monday, November 11, 13
109. 106 Monday, November 11, 13
110. Where We've Been 107 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
111. Where We've Been 108 Monday, November 11, 13
112. Where We've Been 108 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Monday, November 11, 13
113. Where We've Been 108 • Pass It On • Events • Middleware • Lifecycle • Names and Paths • Config • Docs Jason Clark @jasonrclark Ruby Agent Engineer Monday, November 11, 13