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Reducing latency on the web with the Azure CDN - DevSum - SWAG
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Serving up content on the Internet is something our web sites do daily. But are we doing this in the fastest way possible? How are users in faraway countries experiencing our apps? Why do we have three webservers serving the same content over and over again? In this session, we’ll explore the Azure Content Delivery Network or CDN, a service which makes it easy to serve up blobs, videos and other content from servers close to our users. We’ll explore simple file serving as well as some more advanced, dynamic edge caching scenarios.
Maarten BalliauwFollow
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Reducing latency on the web with the Azure CDN - DevSum - SWAG
- Reducing latency on the web with the Azure CDN Maarten Balliauw @maartenballiauw
- Who am I? Maarten Balliauw Antwerp, Belgium Technical Evangelist, JetBrains Founder, MyGet AZUG Focus on web ASP.NET MVC, Azure, SignalR, ... MVP Azure & ASPInsider Big passion: Azure http://blog.maartenballiauw.be @maartenballiauw Shameless self promotion: Pro NuGet - http://amzn.to/pronuget2
- Agenda Why use a CDN? The Azure CDN Blob containers Cloud services Serving dynamic content over the CDN Conclusions
- Why use a CDN?
- How browsers work... Request fetching <html> Download CSS Download images Download JavaScript Download Google Analytics Finite # of concurrent requests per host (and in total)! Bundling/minification Use multiple hosts
- How browsers work... Browser # connections / host Max # connections Chrome 32 6 10 Firefox 26 6 17 IE 9 6 35 IE 10 8 16 IE 11 13 17 Safari 7 6 17 Android 4 6 17 IEMobile 9 6 60 http://www.browserscope.org/?category=network
- Why care? I use bundling and minification!
- Speed of light and TCP don’t like each other US East – US West = 7400 km or 25 ms at speed of light (299792,458 km/second in a vacuum) or 37 ms through fiber optics (66% of SoL, glass refraction index 1.5) TCP request/response, ACK request/response double that 37 ms, add some compute: ~90 ms US East to West Theoretical max. packet size is 64 kB usually +/- 1500 bytes (MTU) TCP slow start http://www.stevesouders.com/blog/2010/07/13/velocity -tcp-and-the-lower-bound-of-web-performance/
- Combine TCP slow start and fiber optics US East – US West ~90ms + TCP slow start 256 kB ~ 10 TCP roundtrips that 90 ms becomes 900 ms... http://www.stevesouders.com/blog/2010/07/13/velocity -tcp-and-the-lower-bound-of-web-performance/
- Cost of web load Serving static files costs CPU Full IIS pipeline for a tiny static file Serving static files costs I/O Files have to be copied from file stream to response stream Why do this? Why not let the server handle our dynamic content? Cookies! Request/response cycle adds the cookie Even for a 1 kB PNG
- So there are some problems on the Internet... Browsers / connections Speed of light / TCP slow start Cost of web load (CPU, I/O and cookies)
- “The Internet sucks and so does your server.” - Andy Cross - @andybareweb
- Workarounds! Browsers / connections Serve some content off a different hostname Speed of light / TCP slow start Move content closer to the user Cost of web load (CPU, I/O and cookies) Serve off a cookieless domain Move content off the web server and let someone else handle it
- The Azure CDN
- The Azure CDN Serve content from storage / cloud service Separate hostname (custom domain possible) Many locations around the globe DNS anycast to get content close to user
- CDN locations (April 1st, 2014) http://msdn.microsoft.com/en-US/library/azure/gg680302.aspx
- How it works: no CDN
- How it works: with CDN
- Demo Creating a CDN endpoint
- What did we just do? First request Second request (on same endpoint) yawn!
- How to use this in real life? Create one/more public blob containers Upload static files in there (CSS, images, scripts, ...) Update your application to the new URLs
- Demo An application with a CDN endpoint
- How to delete content from the CDN? Read a book or 2 and wait (7 days default...) Think about this upfront! If you know expiry, set the Cache-Control header (shorter = more updates) If you don’t, use versioning in query strings Better: use both
- Versioning Enable query strings on the CDN endpoint Use a query string with a meaningful version number CDN will keep a cache per URL per query string /foo/bar?v=1 /foo/bar?v=2 /foo/bar?v=3
- Cloud services will make life easier We had to “manually” upload content to storage May be good, may be cumbersome, depends! Would be nice if we could “deploy and forget” Set a cloud service as the CDN origin Will serve all content from /cdn URL Same cache-control rules as with storage
- Demo Using Cloud Services as the CDN origin
- Best-practices for content on the CDN Set headers! Cache-Control Content-Type Content-Encoding Version content! HTTP compression on origin = HTTP compression on CDN
- Serving dynamic content
- Defining “dynamic content” Content that is generated Parameters from query string, ASP.NET routing, ... And/or based on data Content that refreshes, but not too often Anything > a couple of minutes Examples Charts, images, generated documents, json, API’s, ...
- Demo Serving dynamic content
- Conclusions
- Conclusions Why use a CDN? The Azure CDN Blob containers Cloud services Serving dynamic content over the CDN What have we learned?
- Thank you! http://blog.maartenballiauw.be @maartenballiauw http://amzn.to/pronuget
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