Marrying front with back end

from PHPBenelux 2014

Transcript

1. Marrying front with back end @BastianHofmann
2. Let's talk about... In the next hour I want to talk a bit about
3. Application architecture application architecture and with that I mean how to structure your code
4. Code and component re-use how you can re-use code and components
5. Rapid Development so that you can develop new features quickly without breaking the rest of your application or accumulation lots of technical debt
6. Handling large code-bases especially if your code base becomes larger and larger, developed by big, growing teams
7. Frameworks to the rescue Normally if faced with these problems people say: don't reinvent the wheel, let's look what's already out there, let's use some framework (or some libraries), or if you have a bad case of the not-invented-here syndrom in your company, you are going to develop your own
8. ? languages? one/their own product? agency? long lived, short lived projects? large codebases? frameworks?
9. But I want to be a bit opinionated here: ...
10. Most Web Frameworks are incomplete
11. they oftentimes either care about your backend on the server and serve html pages or apis
12. or they care about your frontend in the client
13. webserver HTML browser JS so the normal flow of a web application is that some server code serves some html (and maybe some apis) to the browser, in the browser there is some (or a lot of) javascript that manipulates the DOM
14. webserver HTML browser JS Ajax and either links to other pages served by the server or does ajax requests back to the server. this concept is mostly true for either traditional apps as well as single page applications
15. webserver HTML browser JS Ajax but the code in both worlds, server and client, is seldom connected
16. de duplication ode duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplication code duplicatio code duplicat code duplic code dup code du code cod co co which leads to lot of code duplication in templates, validation logic, models and lots of boiler plate code for communication between server and client, marshalling data
17. So? so, how can we change this? before i answer this question
18. A few words about me ...
19. I work at ResearchGate, the social network for scientists and researchers
20. ResearchGate gives science back to the people who make it happen. We help researchers build reputation and accelerate scientific progress. On their terms. ‟ the goal is to give...
21. over 3 million users
22. here some impressions of the page
23. you may have read about us in the news recently
24. have this, and also work on some cool stuff
25. have this, and also work on some cool stuff
26. have this, and also work on some cool stuff
27. we are hiring
28. Questions? Ask by the way, if you have any questions throughout this talk, if you don't understand something, just raise your hand and ask.
29. http://speakerdeck.com/u/bastianhofmann the slides will be available on speakerdeck
30. if we take a small peek into a possible future of web application development
31. Meteor http://www.meteor.com or meteor, that try to bridge the gap between server and client. but they are still very alpha, good for prototyping, writing small apps, trying things out, but personally I wouldn't create a big million lines of code web application with 40+ developers yet
32. What about existing applications? and regardless of that, most of you have existing applications
33. Legacy Code with lots of legacy code
34. Incremental Refactoring the way to make the architecture of your existing application better and connect your backend with your frontend code is incremental refactoring, since you hopefully can't afford to sit down, stop development for 6 months and rewrite everything
35. many roads of course like always there are many ways to go about that, which totally depends on you existing code
36. or what i'm going to talk about for the reminder of the talk, what we did at RG
37. status quo so RG: when we started about over a year ago, the status quo was:
38. webserver loadbalancer pgsql memcached mongodb services classic web application, with some soa elements
39. webserver web application was written in php
40. self-written framework, Large, old codebase, some architecture and code smells, but also some nicely done things
41. MVC mvc-like, one page, one controller, one template
42. complicated routing
43. PHP templates templating done in with php scripts on the server
44. on the frontend yui3, but every page was built with custom modules, not much reuse of existing modules but very basic ones (also some legacy pages with yui2, prototype.js and scriptaculous)
45. Duplication and only some Code re- use overall ...
46. We can do better so we sat down and thought ...
47. Components let's rethink the way we are building pages or our whole application and separate it into small components
48. so looking at a page (that's what our profile looked like over a year ago), you can identify lots of small components nested into each other on a page
49. Self contained our goal was that each component is ...
50. Can be addressed and rendered separately and ...
51. Server JS Browser JSON HTML HTML so it should have it's own url, and for seo reasons can just be included in a page rendered to a browser by the server or can be fetched separately or nested within other components by the apps javascript, where we only wanted to transport the data to the client and render it into html there
53. JS is part of the component the javascript to bind on dom events and manipulate the components should be part of the component
54. CSS can be part of the component
55. Share code between server and client and we wanted to share as much code between server and client as possible (considering our heterogeneous architectur, js client, php server)
56. Templates, Validation, Entities,... e.g. ..
57. It needs to be fast of course ... concerning performance as well as development speed and productivity
58. We called them Widgets
59. PHP Controller Mustache Template JavaScript view class Widget Providing data Handling browser events Displaying data CSS so to sum it up an widget contains
60. so if we go back to our page
61. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Institution Menu we see, that it's actually kind of a tree structure, for the sake of this presentation i simplified it slightly, actually our profile consists of over 200 components
62. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Server Request Response Institution i said earlier, that all these components have their own URL. So they can be requested and rendered by the client seperately. For better user experience on the first load or SEO reasons these components can also be bundled together and rendered in a single page load on the backend.
63. LeftColumn Image Menu Server Request Response if we want to fetch the left column separately it looks like this
64. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Institution Menu so you have this tree
65. Widget Requirement this tree structure is achieved through so called widget requirements, why they are called requirements
66. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution that means the profile widget requires: publications, aboutMe, leftColumn and institution
67. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution and Publications requires several publicationItem widgets and leftColumn the Image and the Menu widget
68. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution
69. Remember: self contained remember all these 200 components are supposed to be self contained
70. Do not fetch data directly so something you shouldn't do is fetching this data directly on you server when composing a page or a subpage
71. Sssssssllllooooowww because that would be really slow
72. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Account Account Account Account Account Publication1 Publication2 Publication3 Institution if we take our simplified example, a lot of components need the account of the user that's displayed, while that could be solved with in memory caching, a list of publications each need the publication entity, if we display 20 publications, that would mean 20 database queries, doing it in one query would be much faster though, and you have lot's of stuff like this
73. Require stuff so instead of fetching stuff directly, it's way better to require stuff (that's also why building up the widget tree was done with widget "requirements"
74. http://www.infoq.com/presentations/Evolution-of-Code- Design-at-Facebook/ this concept is actually not that new, one small company who is doing this very much is for example facebook, who also did a very good talk about this a few years back
75. so how does it work? around all your components that just state data (or widget) requirements you need an instance called a preparer
76. Widget Widget Widget Widget Preparer Resolver Resolver Services Connector Interfaces Connector Implementations
77. Widget Widget Widget Widget Preparer Fetch Requirements Resolver Resolver Services Connector Interfaces Connector Implementations the preparer iterates over all components and fetches their requirments
78. Widget Widget Widget Widget Preparer Resolver Resolver Services Connector Interfaces Connector Implementations Batch requirements and pass them to resolvers it batches them together as intelligently as possible, passes the requirements to resolvers
79. Widget Widget Widget Widget Preparer Resolver Resolver Services Connector Interfaces Connector Implementations Call Services as effective as possible (Multi-GET,...) which call the services/storages/etc as effective as possible, or just execute some service class methods
80. Widget Widget Widget Widget Preparer Resolver Resolver Services Connector Interfaces Connector Implementations Attach fetched data to Requirements and pass them back to the preparer the fetched data is attached to the requirements, passed back to the preparer
81. Widget Widget Widget Widget Preparer Resolver Resolver Services Connector Interfaces Connector Implementations Distribute fetched data to the widgets that required it who in turn distributes the fetched data to the components
82. class Widget { /** @var Request */ public $request; public $account; public $scienceDisciplines; public function collect() { return new RequirementCollection([ new EntityRequirement( 'account', Account::class, ['id' => $this->request->get('id')] ), ], function() { return new RequirementCollection([ new ServiceRequirement( 'scienceDisciplines', AccountService::class, 'getScienceDisciplines', ['account' => $this->account] ) ]); }); } } in code... you can imagine if you are not careful this can become some kind of a callback hell
83. Request Cache nice thing is you can cache this stuff intelligently in memory of your current request
84. Multi-GET or use stuff like multi-get
85. Futures or futures / promises
86. class Widget { /** @var Request */ public $request; public $account; public $scienceDisciplines; public function collect() { return new RequirementCollection([ new EntityRequirement( 'account', Account::class, ['id' => $this->request->get('id')] ), ], function() { return new RequirementCollection([ new ServiceRequirement( 'scienceDisciplines', AccountService::class, 'getScienceDisciplines', ['account' => $this->account] ) ]); }); } } as you are seeing here
87. Data dependencies within a widget but oftentimes we have .. so it gets a bit more complex
88. => Callbacks we can use ... for that
89. public function collect() { return new RequirementCollection([ new EntityRequirement( 'account', Account::class, ['id' => $this->request->get('id')] ), ], function() { return new RequirementCollection([ new ServiceRequirement( 'scienceDisciplines', AccountService::class, 'getScienceDisciplines', ['account' => $this->account] ) ]); }); } in code... you can imagine if you are not careful this can become some kind of a callback hell
90. PHP 5.5 Generators http://php.net/manual/de/language.generators.overview.php that's why i'm very excited about generators in php 5.5.
91. <?php function someGenerator() { yield 'start of the generator'; for ($i = 1; $i <= 4; $i++) { // Note that $i is preserved between yields. if ($i % 2 === 0) { yield $i; } } if (rand(1, 2) === 1) { // this closes the generator return; } yield anotherFunction(); // this is also executed } function anotherFunction() { return 'result from another function'; } foreach (someGenerator() as $value) { echo "$value\n"; } start  of  the  generator 2 4 result  from  another  function start  of  the  generator 2 4
92. public function collect() { yield [ new EntityRequirement( 'account', Account::class, ['id' => $this->request->get('id')] ), ]; yield [ new ServiceRequirement( 'scienceDisciplines', AccountService::class, 'getScienceDisciplines', ['account' => $this->account] ) ]; } because then you can write it like this:
93. PHP 5.4 Traits http://us1.php.net/trait that's why i'm very excited about generators in php 5.5.
94. yield [ serviceRequirement( 'job', JobService::getCall()->getById(248) ) ];
95. trait ServiceRequirementFactory { /** @return $this */ public static function getCall() { return new ServiceRequirementFactoryProxy( ! ! ! static::class ! ! ! ); } }
96. class ServiceRequirementFactoryProxy { private $className; public function __construct($className) { $this->className = $className; } public function __call($name, $arguments) { return [ 'serviceClass' => $this->className, 'methodName' => $name, 'arguments' => $arguments ]; } }
97. Data dependencies between Widgets also oftentimes you may have... if only for performance reasons,
98. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution e.g. for a list of publications that you got from a solr search, you may not want to go to the database again to fetch each publication in each list item, but since a list item is supposed to be renderable separately as well, it needs this logic in there
99. Prefills what you can do then is prefilling this data from the parent widget
100. class PublicationKeywordSearch { public $publications; public $publicationListItems = []; public function collect() { yield [ serviceRequirement( 'publications', PublicationService::getCall()->getByKeywords( ['virology', 'cancer'], 10, 0 ) ) ]; foreach ($this->publications as $publication) { yield new WidgetRequirement( 'publicationListItems', PublicationItem::CLASS, [ ! ! ! ! ! ! ! ! 'publicationId' => $publication->getId(), ! ! ! ! ! ! ! ! 'publication' => $publication ! ! ! ! ! ! ! ] ); } } } in code
101. class PublicationItem { public $publicationId; public $publication; public function collect() { yield new RequestDataRequirement('publicationId'); yield [ new EntityRequirement( 'publication', Publication::class, ['id' => $this->publicationId] ) ]; } } that means if the subwidget has a requirment like this, the preparer would directly put the prefilled data in there instead of passing it on to the resolvers
102. Whoa, this looks awfully complicated to debug you're right, it takes a bit of time to get used to program this way, but everyone who joined our company in the last few months since we are doing it says after a week or so, that they actually can't imagine working any other way again (i'll talk more about the benefits later)
103. but still it's complex, so a good thing is taking a bit of effort to make it as transparent as possible to see what happens in your application (which is a very good thing anyways). we have a debug toolbar that shows all the component on the page
104. and you can also drill down into all the iterations the preparer did
108. So that was the backend
109. we now have the date for all the components on our page
110. Rendering so we have now all the data fetched together on our server lets render it now
111. HTML i said earlier we want our widget tree to be renderable on the server side as html
112. JSON and just put out as json and then be rendered on the client side by our javascript
113. Templates and of course we want to reuse our templates
114. Mustache } http://mustache.github.com/ so we decided to use mustache templates, we are actually using twitters mustache implementation called hogan
115. <div id="{{widgetId}}"> <h3> Publications <a href="javascript:" class="js-showAll"> ({{count}}) </a> </h3> <ul> {{#publicationItems}} <li>{{{.}}}</li> {{/publicationItems}} </ul> {{#showLegalFooter}} {{{legalFooter}}} {{/showLegalFooter}} </div> that's what a template may look like
116. Helper Methods there is also a php implementation of mustache, but it's not the fastest and one thing is, that mustache oftentimes relies on small helper functions
117. •nl2br •truncate •pluralize •wordwrap •highlight •... like ... if you now use a php implementation on the server and a js implementation on the client, we have to develop these functions twice ... not a good idea
118. http://pecl.php.net/package/v8js V8js that why we actually execute javascript through a php extension that makes the v8 js library available on the server. so we are executing the same code on the server and on the client to render the same templates. suprise: it's acutally really really fast
119. JavaScript so we handled templates and rendering, the backend controllers that provide the data, on the javascript side in the client each component can have a view object to bind on DOM events
120. WidgetViews
121. <div id="{{widgetId}}"> <h3> Publications <a href="javascript:" class="js-showAll"> ({{count}}) </a> </h3> <ul> {{#publicationItems}} <li>{{{.}}}</li> {{/publicationItems}} </ul> {{#showLegalFooter}} {{{legalFooter}}} {{/showLegalFooter}} </div> remember this template
122. YUI.add('views.publicationList', function (Y) { Y.views.publicationList = Y.Base.create(Y.WidgetView, { events : { '.js-showALl' : { click : 'showALl' } }, showAll : function () { var node = this.get('container'); node.addClass('loading'); Y.loadWidget(‚/publications/all', { keywords : this.data.keywords }, function (widget) { widget.render({ replace : node }); }); } }); }); here is an example
123. if you think about this a bit more, every component having it's own template, javascript and maybe css
124. http://twitter.github.io/flight/ twitter, check out flight.js
125. http://facebook.github.io/react/ by the way: if you’ll have a look at react: it is strikingly similar
126. http://www.youtube.com/watch?v=fqULJBBEVQE .. this is exactly what web components is about. they have their own html, css, js and are even more sandboxed through a shadow dom to limit interactions between different components. an example for webcomponents are the browser controls for videos or forms by the way.
127. http://www.polymer-project.org/
128. <polymer-element name="tk-element" attributes="owner color"> <template> <span>This is <strong>{{owner}}</strong>'s tk-element.</span> <span id="el" style="color: {{color}}">Not ready...</span> </template> <script> Polymer('tk-element', { owner: "Bastian", color: "red", ready: function() { this.$.el.innerText = this.owner + " is ready!"; } }); </script> </polymer-element>
129. <!DOCTYPE html> <html> <head> <script src="bower_components/platform/platform.js"> </script> <link rel="import" href="elements/tk-element.html"> </head> <body> <tk-element color="blue"></tk-element> </body> </html>
130. Benefits
131. Enables developers to only focus on their components
132. Rapid prototyping
133. Easier Refactoring even if the implementation of one component is very ugly and crude, at least it's encapsulated (hopefully tested) and you can either leave it or revisit this component later on
134. Error Handling also error handling can be really simplified and end-user friendly
135. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution so going back to our widget tree
136. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu EXCEPTION Institution if an exception occurs in one of our components while fulfilling a requirement that is not optional
137. Profile Publications Publication Publication Publication LeftColumn Image Menu Institution we just deactivate this component and the rest of the page is still functional
138. Experiments (A/B Testing) also this approach simplifies testing, and with that i mean A/B testing
139. we are doing this excessively, and have over 90 or so experiments with sometimes over 20 variants running. the way we can do this quickly and easily is by just switching components for the different variants
140. Caching of Components also you can cache the components easily in a varnish
141. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu <esi:include src="..." /> Institution because every component has it's own url you can just render out a esi placeholder instead of the widget to tell varnish to fetch it separately and provided it has caching headers, get it out of the cache
142. Easy re-using of components
144. Load components asynchronously the same way you can also load components of the widget tree asynchronously
145. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu <div id="placeholder"></div> <script>loadWidget('/aboutMe', function(w) { w.render({ replace : '#placeholder' }); })</script> Institution so instead of rendering the widget you render a placeholder dom element and a script tag that loads the widget with an ajax request and then renders it on the client side
146. BigPipe https://www.facebook.com/note.php? note_id=389414033919 even more sophisticated: something facebook calls bigpipe (we call it nozzle)
147. if you look at your widget tree you can mostly identify larger parts, which are widgets itself
148. Profile Menu Header LeftColumn RightColumn like this, so what you can do to dramatically increase the perceived load time is prioritizing the rendering
149. so our http request looks like this, first you compute and render the important parts of the page, like the top menu and the profile header as well as the rest of the layout, for the left column and right column which are expensive to compute you just render placeholders and then flush the content to the client so that the browser already renders this
150. still in the same http request you render out the javascript needed to make the already rendered components work, so people can use the menu for example
151. still in the same http request you then compute the data for the left column and render out some javascript that takes this data and renders it into the components template client side and then replaces the placeholder with the rendered template
152. still in the same request you then can do this with the right column -> flush content as early as possible, don't wait for the whole site to be computed
153. pushState and if you are at that, when you switch pages, you can also just load the differences between and use pushState to change the url (if supported) to make your app faster
154. Profile Publications Publication Publication Publication AboutMe LeftColumn Image Menu Institution
155. Profile Questions Question Question Question AboutMe LeftColumn Image Menu Institution
156. Conclusion?
157. Think about your architecture
158. Refactor and make it better continuously
159. Frontend and backend are part of the same application
160. Don't rewrite your whole codebase in one go
161. https://joind.in/10279
162. http://twitter.com/BastianHofmann http://lanyrd.com/people/BastianHofmann http://speakerdeck.com/u/bastianhofmann mail@bastianhofmann.de thanks, you can contact me on any of these platforms or via mail.
163. Start of an opensource implementation https://github.com/P2EE