Get to know the browser better   and write faster web apps
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Get to know the browser better and write faster web apps

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Get to know the browser better   and write faster web apps Get to know the browser better and write faster web apps Presentation Transcript

  • © 2013 SAP Portals. All rights reserved. 1 Lior Bar-On, Senior Development Architect @ SAP Sept. 2013 Public
  • © 2013 SAP Portals. All rights reserved. 2 About Me   ‫שלי‬ ‫הבלוג‬(‫בעברית‬:)http://www.softwarearchiblog.com/ http://www.linkedin.com/in/liorbo
  • © 2013 SAP Portals. All rights reserved. 3 Agenda The Server The Network The Browser
  • © 2013 SAP Portals. All rights reserved. 4 The Network The Network The Server The Browser
  • © 2013 SAP Portals. All rights reserved. 5 A Web App that loads is a Miracle! Load HTML file DNS lookup Establish TCP Conn. (3-way handshake) HTTP request @Cold Connection HTML Parsing starts <script> tag => “Stop The World” ForEach Script file:  (Optional) DNS lookup  (Optional) 3-way handshake + TLS handshake (“4-way”)  (Optional) http request over a (cold) connection Continue HTML parsing…. t
  • © 2013 SAP Portals. All rights reserved. 6 TCP Congestion Control: Slow Start (sending 20KB of data) Cold Connection Warn Connection Segment = 1460 bytes Header = 40 bytes
  • © 2013 SAP Portals. All rights reserved. 7 An “Underwater Cable” won’t save ya!
  • © 2013 SAP Portals. All rights reserved. 8 How Does it works? Hardware improves all the time CPU / Memory Network Browsers Optimizations Client-Side Cache Keep Alive DNS pre-fetch TCO pre-connect Network Optimizations: Content Delivery Networks (CDNs) Developers can do much more!
  • © 2013 SAP Portals. All rights reserved. 9 Main Pain Point of Modern Networks: Latency “average” latency is typically ~200ms, +200ms for 3G access source
  • © 2013 SAP Portals. All rights reserved. 10 Tactics dealing with the Network Reduce the number of Roundtrips Lazy Loading Caching Domain Sharding Unification Minification
  • © 2013 SAP Portals. All rights reserved. 11 Tactic: Reduce number of Roundtrips / redirects Latency is paid for each roundtrip done. Eliminate (e.g. 404s, resources not being used) Unify (later) Lazy-Load (later) Redirects require a new HTTP request cycle Redirect = a significant waste e.g. redirect to “m.mysite.com” source: http archive
  • © 2013 SAP Portals. All rights reserved. 12 Tactic: Lazy Loading Load resources (scripts, ajax calls, (images)) only when they are needed. Dynamic JavaScript loading libraries:  LABjs  require.js  Lsjs  ControlJS Manually: $('head').append( ... );
  • © 2013 SAP Portals. All rights reserved. 13 Tactic: Caching Distinguish between “Cachable” vs. “Non-Cachable” HTTP Methods: Some Methods (GET, HEAD) will be cached by the “network” Unsafe Methods (POST, PUT, DELETE, OPTIONS) will not be cached by the “network” Use appropriate HTTP headers to define a proper caching policy Such as:  Cache-control / expires  If-Modified  ETags POST method can become cachable with proper headers, at least in theory
  • © 2013 SAP Portals. All rights reserved. 14 Domain Sharding Distribute resources over multiple hostname to increase connection parallelism Effectiveness is nowadays questionable (argument for, argument against) Even if you do:  Only on domains proven to require many files  Shard no more than once A new method rising: “Domain UnSharding”: Assembling large, unique resources to a single host can enjoy “connections warm-up”. Images, fonts and niche JavaScript libraries - are a good candidates example.com = 1.1.1.1 img.example.com = 1.1.1.1 DNS Browser consult 6 x example.com 6 x img.example.com Overall: 12 connections! << 1.1.1.1 >> Server connections:
  • © 2013 SAP Portals. All rights reserved. 15 Tactic: Unification Working with small source files is a good programming practice. So - crunch JavaScript and CSS files Yahoo’s YUI Compressor Google Closure Compiler CSSO (for CSS files) etc. source: http archive
  • © 2013 SAP Portals. All rights reserved. 16 Tactic: Unification (2) Sprites Create 1 image to replace many Not just for image files (e.g. howler.js) Data URIs Note: DataURI increase resource size by 37%
  • © 2013 SAP Portals. All rights reserved. 17 Tactic: Minification JavaScript Minification tools can reduce 50%-90% of the file’s size Being compressed into:
  • © 2013 SAP Portals. All rights reserved. 18 Tactic: Minification(2) CSS minification tools can reduce 30%-50% of the file’s size Optimize images size and compression - can save much size. Enabling GZIP compression on textual files (even if minified) can save you some network bytes. Bitmap Vector SVG JPG compression? PNG Bit depth? Lossy PNG ? ? ? Bitmap reduce size? ? ?
  • © 2013 SAP Portals. All rights reserved. 19 Real Life Experience
  • © 2013 SAP Portals. All rights reserved. 20 WebPageTest: Results
  • © 2013 SAP Portals. All rights reserved. 21 WebPageTest: Some Data provided
  • © 2013 SAP Portals. All rights reserved. 22 WebPageTest: Connection View
  • © 2013 SAP Portals. All rights reserved. 23 Inbound Alternative: Chrome Dev Tools
  • © 2013 SAP Portals. All rights reserved. 24 The Browser The Network The Server The Browser
  • © 2013 SAP Portals. All rights reserved. 25 The Web Browser source: statcounter
  • © 2013 SAP Portals. All rights reserved. 26 The Browser Internals - engines Browser Rendering Engine Safari (iOS, win or Mac) Webkit Chrome, Opera Blink (a recent fork of Webkit) Firefox Gecko Internet Explorer Trident Internet Explorer for Mac Tasman Browser JavaScript Engine ECMAScript 5.1 Support since Safari (iOS, win or Mac) javaScriptCore (aka Nitro) SF5.1* Chrome, Opera V8 Chrome13 Firefox SpiderMonkey JIT part called ionMoney (since FF18) FF4 Internet Explorer Chakra (since IE9) IE9*
  • © 2013 SAP Portals. All rights reserved. 27 Typical Browser HTML rendering flow HTML file DOM Tree (aka content model) 1: parse Style Tree (aka style ruleSet, CSSOM) CSS file 2: parse 2: load Render Tree (aka frame tree) 3: merge 3: merge Canvas 5: render Layout 4: layout / re-flow JavaScript file 2: update 2: update 2: load 6: draw on screen Source: d.baron
  • © 2013 SAP Portals. All rights reserved. 28 Problems that may occur with the Browser’s Rendering Model “Stop the World” on initial page load Doing Unnecessary work (“Layout trashing”, “Paint trashing”) Single thread The Browser is not well-known to developers
  • © 2013 SAP Portals. All rights reserved. 29 “Stop The World” blocks other downloads (images in IE, iframes); scripts are loaded and executed serially; blocks rendering during parse-execute
  • © 2013 SAP Portals. All rights reserved. 30 3 interaction milestones 0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result. 1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay. Normally, no special feedback is necessary during delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of operating directly on the data. 10 seconds is about the limit for keeping the user's attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect.
  • © 2013 SAP Portals. All rights reserved. 31 Tactics dealing with the Browser Postpone Script Execution Add styles before DOM Elements Be aware of DOM Tree’s Write Buffer Offload work to other threads
  • © 2013 SAP Portals. All rights reserved. 32 Tactic: Postpone Script Execution Either:  Move Script to the end of the file (after <body> tag)  Add Script Dynamically to <head> tag: $('head').append( ... );  Use “async” and “defer” attributes <script src=“…” async></script>  Simply, use require.js / LABjs / etc.
  • © 2013 SAP Portals. All rights reserved. 33 Tactic: Add styles before DOM Elements Inserting Style tree element is more expensive than inserting DOM element. We also want nice visualization on the screen early (perceived performance) Therefore:  Inside the <HEAD>, put all CSS files first.  Prefer jQuery’s data() over addClass()  Minimize use of CSSOM, e.g.: myStyle.insertRule(…) DOM Tree (aka content model) Style Tree (aka style ruleSet, CSSOM) Render Tree (aka frame tree) 3: merge 3: merge
  • © 2013 SAP Portals. All rights reserved. 34 2 Code Examples… Which Example looks Much better for performance?
  • © 2013 SAP Portals. All rights reserved. 35 Tactic: Be aware of DOM Tree’s Write Buffer A little theory: Flush will happen:  At DOM read operation, e.g. element.height  Every 16.6ms (to achieve 60fps) Style Tree DOM Tree Render Tree DOM API Read (B) Write Buffer Read (A) write Flush changes derived fromderived from
  • © 2013 SAP Portals. All rights reserved. 36 Tactic: Be aware of DOM Tree’s Write Buffer (2) R/W/R/W/R/W/R/W/R/W = ~250ms RRRRRRR/WWWWWW = ~20ms source
  • © 2013 SAP Portals. All rights reserved. 37 Another example Could be so much better as:
  • © 2013 SAP Portals. All rights reserved. 38 Tactic: offload work to other threads Browser has a single thread that executes JavaScript (per browser tab) When the thread is busy, the following is being blocked: Event handling (e.g. Click, Resize) setTimeout / setInterval Possibly rendering What can be done? SetTimeout(myFunc, 0); Use CSS Animations transform: translateZ(0); read more Use Web Workers for intensive calculations / network activity Heap Queue Stack Thread Closure Closure Closure Closure Closure Closure Closure Closure Closure Closure global variables Context (“window” object) public part private part pull push “document” object (DOM)
  • © 2013 SAP Portals. All rights reserved. 39 Chrome Dev Tools’ Timeline is your best friend
  • © 2013 SAP Portals. All rights reserved. 40 Thank You Lior Bar-On baronlior@gmail.com (Hebrew) Blog: http://www.softwarearchiblog.com/