Abusing JavaScript to measure Web Performance, or, "how does boomerang work?"

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While building boomerang, we developed many interesting methods to measure network performance characteristics using JavaScript running in the browser. While the W3C's NavigationTiming API provides access to many performance metrics, there's far more you can get at with some creative tweaking and analysis of how the browser reacts to certain requests.

In this talk, I'll go into the details of how boomerang works to measure network throughput, latency, TCP connect time, DNS time and IPv6 connectivity. I'll also touch upon some of the other performance related browser APIs we use to gather useful information.

http://www.nywebperformance.org/events/78566362/

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Abusing JavaScript to measure Web Performance, or, "how does boomerang work?"

  1. 1. • Philip Tellis• .com• philip@lognormal.com• @bluesmoon• geek paranoid speedfreak• http://bluesmoon.info/ NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 1
  2. 2. I <3 JavaScriptNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 2
  3. 3. So much that I wore Mustache socks to my wedding NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 3
  4. 4. I’m a Speedfreak (the network kind)NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 4
  5. 5. We measure real user website performanceNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 5
  6. 6. This talk is (mostly) about how we abuse JavaScript to do it NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 6
  7. 7. Abusing JavaScript to Measure Web Performance Philip Tellis / philip@lognormal.com NY #WebPerf Meetup / 2012-09-13NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 7
  8. 8. First, a note about the code Note that in the code that follows, + new Date is equivalent to new Date().getTime() NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 8
  9. 9. 1 LatencyNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 9
  10. 10. Arrange the following in order of increasing signal latency overa fixed distance: • Electricity through copper • Smoke Signals • Light through Fibre • Pulsar NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 10
  11. 11. 1 Blinking Lights It takes about 16ms for light to get from SF to NYC (24ms through fibre) ... NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 11
  12. 12. 1 Blinking Lights It takes about 16ms for light to get from SF to NYC (24ms through fibre) Though it takes about 100ms to ping... why? NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 11
  13. 13. 1 HTTP NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 12
  14. 14. So to measure latency, we need to send 1 packet each way, and time it NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 13
  15. 15. 1 Network latency in JavaScript var ts, rtt, img = new Image; img.onload=function() { rtt=(+new Date - ts) }; ts = +new Date; img.src="/1x1.gif"; NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 14
  16. 16. 1 Notes • 1x1 gif is 35 bytes • including HTTP headers, is smaller than a TCP packet • Fires onload on all browsers • 0 byte image fires onerror • which is indistinguishable from network error NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 15
  17. 17. 2 TCP handshakeNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 16
  18. 18. 2 ACK-ACK-ACK NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 17
  19. 19. 2 Connection: keep-alive NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 18
  20. 20. 2 Network latency & TCP handshake in JavaScript var t=[], tcp, rtt; var ld = function() { t.push(+new Date); if(t.length > 2) // run 2 times done(); else { var img = new Image; img.onload = ld; img.src="/1x1.gif?" + Math.random() + ’=’ + new Date; } }; var done = function() { rtt=t[2]-t[1]; tcp=t[1]-t[0]-rtt; }; ld(); NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 19
  21. 21. Notice that we’ve ignored DNS lookup time here... how would you measure it? NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 20
  22. 22. Network Throughput 3NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 21
  23. 23. 3 Measuring Network Throughput data_length download_time NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 22
  24. 24. Should you fly a 747 or a 737? • A 747 seats 400+ passengers • A 737 seats about 150 • Both take about the same time to fly from SFO to BOS • A 747 takes longer to load and unload than 3 737s in parallel The best selling aircraft to date is the 737 NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 23
  25. 25. 3 Network Throughput in JavaScript // Assume global object // image={ url: ..., size: ... } var ts, rtt, bw, img = new Image; img.onload=function() { rtt=(+new Date - ts); bw = image.size*1000/rtt; // rtt is in ms }; ts = +new Date; img.src=image.url; NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 24
  26. 26. 3 Measuring Network Throughput If it were that simple, I wouldn’t be doing this talk. NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 25
  27. 27. 3 TCP Slow Start NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 26
  28. 28. 3 Measuring Network Throughput So to make the best use of bandwidth, we need resources that fit in a TCP window NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 27
  29. 29. 3 There is no single size that will tax all available networks http://www.yuiblog.com/blog/2010/04/08/analyzing-bandwidth-and-latency/ NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 28
  30. 30. 3 Network Throughput in JavaScript – Take 2 // image object is now an array of multiple images var i=0; var ld = function() { if(i>0) image[i-1].end = +new Date; if(i >= image.length) done(); else { var img = new Image; img.onload = ld; image[i].start = +new Date; img.src=image[i].url; } i++; }; NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 29
  31. 31. 3 Measuring Network Throughput Slow network connection, meet really huge image NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 30
  32. 32. 3 Network Throughput in JavaScript – Take 3 var img = new Image; img.onload = ld; image[i].start = +new Date; image[i].timer = setTimeout(function() { image[i].expired=true }, image[i].timeout); img.src=image[i].url; NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 31
  33. 33. 3 Network Throughput in JavaScript – Take 3 if(i>0) { image[i-1].end = +new Date; clearTimeout(image[i-1].timer); } NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 32
  34. 34. 3 Network Throughput in JavaScript – Take 3 if(i >= image.length || (i > 0 && image[i-1].expired)) { done(); } NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 33
  35. 35. 3 Measuring Network Throughput Are we done yet? NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 34
  36. 36. 3 Measuring Network Throughput Are we done yet? sure... NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 34
  37. 37. 3 Measuring Network Throughput Except network throughput is different every time you test it NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 35
  38. 38. Statistics to the Rescueflickr/sophistechate/4264466015/ NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 36
  39. 39. 3 Measuring Network Throughput The code for that is NOT gonna fit on a slide NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 37
  40. 40. But this is sort of what we see world-wide NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 38
  41. 41. And it’s different for different countries This is India NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 39
  42. 42. 4 DNSNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 40
  43. 43. 4 Measuring DNS time_with_dns − time_without_dns NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 41
  44. 44. 4 Measuring DNS in JavaScript var t=[], dns, ip, hosts=[’http://hostname.com/’, ’http://ip.ad.dr.ess/’]; var ld = function() { t.push(+new Date); if(t.length > hosts.length) done(); else { var img = new Image; img.onload = ld; img.src=hosts[t.length-1] + "/1x1.gif"; } }; var done = function() { ip=t[2]-t[1]; dns=t[1]-t[0]-ip; }; ld(); NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 42
  45. 45. 4 Measuring DNS • What if the IP changes? • What if DNS is cached? • What if you map DNS based on geo location? NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 43
  46. 46. 4 Wildcard DNS Entries *.foo.com → IP address NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 44
  47. 47. 4 Measuring DNS in JavaScript – take 2 var base_url="http://*.foo.com/", timers = {}, gen_url=""; function start() { var random = Math.random().toString(36), cache_bust = Math.random(), img = new Image(); gen_url = base_url.replace(/*/, random); img.onload = A_loaded; timers.start = +new Date; img.src = gen_url + "image-l.gif?t=" + cache_bust; } NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 45
  48. 48. 4 Measuring DNS in JavaScript – take 2 function A_loaded() { var cache_bust = Math.random(), img = new Image(); img.onload = B_loaded; timers.a_loaded = +new Date; img.src = gen_url + "image-l.gif?t=" + cache_bust; } I’ll let you figure out B_loaded NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 46
  49. 49. 4 Measuring DNS Full code in boomerang’s DNS plugin NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 47
  50. 50. 5 IPv6NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 48
  51. 51. 5 Measuring IPv6 support and latency 1 Try to load image from IPv6 host • If timeout or error, then no IPv6 support • If successful, then calculate latency and proceed 2 Try to load image from hostname that resolves only to IPv6 host • If timeout or error, then DNS server doesn’t support IPv6 • If successful, calculate latency NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 49
  52. 52. 5 Measuring IPv6 support and latency Full code in boomerang’s IPv6 plugin Note, only run this if you know IPv6 is supported by the client NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 50
  53. 53. 6 Other StuffNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 51
  54. 54. 6 Other Stuff We Measure • NavTiming – navtiming.js • navigation.connection.type – mobile.js • window.performance.memory – memory.js – Chrome 22 reporting now. • Number of DOM nodes and byte size of HTML – memory.js NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 52
  55. 55. And we try to do it fastNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 53
  56. 56. – .done()NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 54
  57. 57. Code/References • http://lognormal.github.com/boomerang/doc/ (BSD Licensed) • www.lognormal.com NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 55
  58. 58. • Philip Tellis• .com• philip@lognormal.com• @bluesmoon• geek paranoid speedfreak• http://bluesmoon.info/ NY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 56
  59. 59. Thank you Ask me about a discount codeNY #WebPerf Meetup / 2012-09-13 Abusing JavaScript to Measure Web Performance 57

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