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Embracing the Network — DIBI Conf, March 2016

Embracing the Network — DIBI Conf, March 2016

This version of the talk was originally presented at DIBI Conf in Edinburgh, Scotland on the 18th March 2016.

The network is intrinsically unreliable. More so, the network is out of your control as a developer. Therefore, we must design systems which embrace the unpredictability of the network and defend against it all costs. How can you prioritise the delivery of your core content? What best-practices can you use to optimise your assets? How can we design interfaces which adapt and respond to changing network conditions? And finally, how are new APIs such as ServiceWorker changing the way we think about the network?

During this talk Patrick will share his experiences delivering high-performance websites to millions of users over the past 3 years at The Guardian and Financial Times. Which – most importantly – are resilient to the network.

Patrick Hamann

March 26, 2016

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  1. Embracing the network Patrick Hamann — DIBI, March 2016

    Modern techniques for building resilient front ends !
  2. https://en.wikipedia.org/wiki/Fallacies_of_distributed_computing 1. The network is reliable. 2. Latency is zero.

    3. Bandwidth is infinite. 4. The network is secure. 5. Topology doesn't change. 6. There is one administrator. 7. Transport cost is zero. 8. The network is homogeneous. 
 The fallacies of distributed computing 
  3. Multiple points of failure Dmytrii Shchadei — http://www.slideshare.net/metrofun/reduce-mobile-latency " #

    # # $ Internal latency Firewalls, Load Balancers, Servers % Internet routing latency CDNs, ISPs, Caches, Proxies Control plane latency ~600ms on average UK 3G connection ~200ms
  4. Baking in the assumption that everything can and will fail

    leads you to think differently about how you solve problems. 
 SAM NEWMAN — BUILDING MICROSERVICES, O’REILLY 2015 http://shop.oreilly.com/product/0636920033158.do
  5. A single point of failure (SPOF) is a part of

    a system that, if it fails, will stop the entire system from working. SPOFs are undesirable in any system with a goal of high availability or reliability, be it a business practice, software application, or other industrial system. https://en.wikipedia.org/wiki/Single_point_of_failure
  6. User Timing API http://www.w3.org/TR/resource-timing/ window.performance.mark(“fonts-loaded“); <script> window.performance.mark("css-start"); </script>
 <link rel="stylesheet"

    href="/main.css" /> <link rel="stylesheet" href="/fonts.css" /> <script> performance.mark("css-end"); performance.measure("css-loading", "css-start", "css-end"); </script>
  7. • Test 1st and 3rd party dependencies for SPOFs •

    Use network shaping to simulate mobile conditions • Monitor metrics contextual to your business • Mark and measure your custom events • Alert if metrics pass their thresholds/budgets
  8. Delay User perception 0 - 100ms Instant 100 - 300ms

    Small perceptible delay 300 - 1000ms Machine is working 1000+ ms Likely mental context switch 10,000+ ms Task is abandoned
  9. • Respond within a 1000ms • Avoid loading spinners •

    Consider using skeleton screens • Re-use familiar UI patterns within error messaging • Use human friendly copy, especially in error states • Visualise the state of the network
  10. Loading fonts https://tabatkins.github.io/specs/css-font-rendering/ Chrome Opera Safari Firefox IE Timeout 3s

    3s no timeout 3s 0 Fallback Yes Yes n/a Yes Yes Swap Yes Yes n/a Yes Yes
  11. CSS Font Rendering Controls Module https://tabatkins.github.io/specs/css-font-rendering/ @font-face { font-family: 'MyShinyFont';

    src: url('http://fonts.ft.com/async.woff2'); font-display: swap; } @font-face { font-family: 'MyBlockingFont'; src: url: url('http://fonts.ft.com/blocking.woff2'); font-display: block; }
  12. Cache only self.addEventListener('install', function(event) { event.waitUntil( caches.open(cacheName).then(function(cache) { return cache.addAll([

    ‘http://fonts.ft.com/fonts.css', 'http://fonts.ft.com/serif', 'http://fonts.ft.com/sans-serif' ]); }) ); }); https://jakearchibald.com/2014/offline-cookbook
  13. Cache only https://jakearchibald.com/2014/offline-cookbook self.addEventListener('fetch', function(event) { // If this is

    a request for font file if (/fonts\.ft\.com/.test(event.request)) { // If a match isn't found in the cache, the response // will look like a connection error event.respondWith(caches.match(event.request)); } });
  14. Stale-while-revalidate self.addEventListener('fetch', function(event) { // Get stale from cache event.respondWith(

    caches.open(cacheName).then(function(cache) { return cache.match(event.request).then(function(response) { // If in cache relvalidate var network = fetch(event.request).then(function(response){ if(response.status < 400) { cache.put(event.request, response.clone()); } }); // Return stale or network if none return response || network; }); }) ); }); https://jakearchibald.com/2014/offline-cookbook
  15. Stale-if-error self.addEventListener('fetch', function(event) { // Always fetch response from the

    network event.respondWith( fetch(event.request).then(function(response) { // If we received an error response if(!response.ok) { // If we received an error response return caches.match(event.request) } else { // Response was healthy so update cached version cache.put(event.request, response.clone()); return response; } }) ); });
  16. Timeout race function timeout(delay) { return new Promise(function(resolve, reject) {

    setTimeout(function() { resolve(new Response('', { status: 408, statusText: 'Request timed out.' })); }, delay); }); } self.addEventListener('fetch', function(event) { // Attempt to fetch with timeout event.respondWith(Promise.race([timeout(2000), fetch(event.request)])); });
  17. • Pre-fetch and cache critical resources • Serve stale and

    revalidate • Serve stale if error • Always use timeouts • Queue and batch requests • Treat the network as an enhancement!
  18. Background sync navigator.serviceWorker.ready.then(function(registration) { regitration.periodicSync.register({ tag: 'get-latet-news', // default: ''

    minPeriod: 12 * 60 * 60 * 1000, // default: 0 powertState: 'avoid-draining', // default: 'auto' networkState: 'avoid-cellular' // default: 'online' }).then(function(periodicsyncReg) { // success }, function() { // failure }); });