Flipping out with Feature Flags & Toggles - PHP Yorkshire 2017

1. FLIPPING OUT WITH FEATURE FLAGS & TOGGLES PHP YORKSHIRE 2017 @MICHAELCULLUMUK
2. ME?
3. MICHAEL CULLUM @MICHAELCULLUMUK
4. BACK TO BASICS
5. CONDITIONALS <?php if (true) { oneAction(); } else { alternativeAction(); }
6. CONDITIONALS <?php if ($enabled) { oneAction(); } else { alternativeAction(); }
7. FEATURE FLAG <?php if (featureEnabled('twitter_seen')) { oneAction(); } else { alternativeAction(); }
8. WHAT’S IN A NAME?
9. SWIFT MAILER
10. SWIFT MAILER swiftmailer: disable_delivery: ~
11. SWIFT MAILER <?php if (isset($mailer[‘disable_delivery'])) { $transport = 'null'; $container->setParameter('swiftmailer.enabled', false); } else { $container->setParameter('swiftmailer.enabled', true); }
12. SWIFT MAILER <?php if (isset($mailer[‘disable_delivery'])) { $transport = 'null'; $container->setParameter('swiftmailer.enabled', false); } else { $container->setParameter('swiftmailer.enabled', true); }
13. ALTERNATIVE TO BRANCHING?
14. VARY BY: ENVIRONMENT USER
15. DIFFERENT SUBSET OF USERS
16. A/B TESTING
17. BOOKING.COM MODEL
18. TEST IN PRODUCTION
19. MONOLITHIC REPOSITORIES
20. TEST A MATRIX OF CHANGES
21. MANAGING YOUR FLAGS
22. RETRIEVING FEATURE FLAG VALUES
23. SPLIT IT OUT <?php interface FeatureFlags { function isEnabled(string $flag): boolean }
24. HARDCODED <?php function isEnabled(string $flag): boolean { if ($flag == 'profile') { return true; } return false; } if (isEnabled('profile')) { newProfileMagic(); }
25. HARDCODED <?php function isEnabled(string $flag): boolean { if ($flag == 'profile') { return true; } return false; } if (isEnabled('profile')) { newProfileMagic(); }
26. PARAMETERS IN CONFIG FILES <?php function isEnabled(string $flag): boolean { if ($flag == 'mailDelivery') { return $this->container->getParameter('swiftmailer.enabled', $flag); } elseif (isset($this->container->getParameter(sprintf('flag.%s', $flag)))) { return $this->container->getParameter(sprintf('flag.%s', $flag)); } return false; }
27. CACHE function isEnabled(string $flag): boolean { $cache = $this->cache; $flag = $cache->getItem(sprintf('flag.%s', $flag)); if (!$flag->isHit()) { $flag->get(); } return false; }
28. DATABASE
29. SETTING FEATURE FLAG VALUES
30. DATABASE
31. CODEBASE
32. USING THEM CLEANLY
33. TWIG {% if isFeatureEnabled('showCfpForm') %} {{ form(form) }} {% endif %}
34. TWIG <?php namespace AppBundle\Twig; class AppExtension extends \Twig_Extension { public function getFunctions() { return array( new \Twig_SimpleFunction('isEnabled', array($this, 'isEnabled')), ); } //.. }
35. COMPLEXITY <?php if ($container->getParameter('profileFeature')) { if ($container->getParameter('newProfileStyle')) { if ($container->getParameter('newProfileStyleButtons')) { enableButtons(); } if ($container->getParameter('myNewCoolProfilePic')) { renderPicture(); if ($container->getParameter('newProfileRenderEngine')) { tryDifferentRenderEngine(); } } renderNewProfiler(); } else { // Render the legacy profile } }
36. COMPLEXITY <?php if ($container->getParameter('profileFeature')) { if ($container->getParameter('newProfileStyle')) { if ($container->getParameter('newProfileStyleButtons')) { enableButtons(); } if ($container->getParameter('myNewCoolProfilePic')) { renderPicture(); if ($container->getParameter('newProfileRenderEngine')) { tryDifferentRenderEngine(); } } renderNewProfiler(); } else { // Render the legacy profile } }
37. COMPLEXITY <?php if ($container->getParameter('profileFeature')) { if ($container->getParameter('newProfileStyle')) { if ($container->getParameter('newProfileStyleButtons')) { enableButtons(); } if ($container->getParameter('myNewCoolProfilePic')) { renderPicture(); if ($container->getParameter('newProfileRenderEngine')) { tryDifferentRenderEngine(); } } renderNewProfiler(); } else { // Render the legacy profile } }
38. CONTROLLERS
39. CONTROLLERS - YAML profile: path: /profile/{user} defaults: _controller: DemoBundle:Profile:legacy _alt: DemoBundle:Default:new _flag: newProfile
40. CONTROLLERS - EVENT <?php public function onKernelRequest($event) { $flag = $event->getRequest->attributes->get('_flag'); $alternate = $event->getRequest->attributes->get('_alt'); if (isEnabled($flag)) { $event->getRequest->attributes->set(‘controller’, $alternate); } }
41. CONTROLLERS - EVENT <?php public function onKernelRequest($event) { $flag = $event->getRequest->attributes->get(‘_flag'); $alternate = $event->getRequest->attributes->get(‘_alt'); if (isEnabled($flag)) { $event->getRequest->attributes->set(‘_controller’, $alternate); } if (!isset($alternate) && isset($flag) && !isEnabled($flag)) { throw new NotFoundHttpException(); } }
42. CONTROLLERS - EVENT <?php public function onKernelRequest($event) { $flag = $event->getRequest->attributes->get(‘_flag'); $alternate = $event->getRequest->attributes->get(‘_alt'); if (isEnabled($flag)) { $event->getRequest->attributes->set(‘_controller’, $alternate); } if (!isset($alternate) && isset($flag) && !isEnabled($flag)) { throw new NotFoundHttpException(); } }
43. SERVICE FACTORIES
44. NON-GENERIC FACTORY <?php class ProfileFactory { public function create(): ProfileInterface { return isEnabled(‘newProfile’) ? $container->get(‘newProfile’) : $container->get(‘legacyProfile’); } }
45. GENERIC FLAGS FACTORY <?php class FlagsFactory { public function createService(string $flag, $service, $alternate) { return isEnabled($flag) ? $container->get($service) : $container->get($alternate); } }
46. GENERIC FLAGS FACTORY services: app.flagsFactory: class: AppBundle\FlagsFactory app.profileManager: class: AppBundle\Profile\ProfileManager factory: ['@app.flagsFactory', createService] arguments: - newProfile - legacyProfileManager - newProfileManager
47. REMOVE THEM LATER OR NOT?
48. ALLOWS YOU TO
49. BRANCHING WITHOUT CONFLICTS OR VCS
50. TEST IN PRODUCTION
51. SLOW ROLLOUT
52. FUNCTIONALITY ON DIFFERENT ENVIRONMENTS
53. A/B TESTING
54. CLEANLY
55. DATABASE OR CONFIGURATION FILES
56. AVOIDING LARGE CONDITIONALS
57. THANKS @MICHAELCULLUMUK
58. FLIPPING OUT WITH FEATURE FLAGS & TOGGLES PHP YORKSHIRE 2017 @MICHAELCULLUMUK