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Speed up your site with Varnish
Varnish is a caching tool that can speed up websites by caching HTTP responses in memory and skipping Apache, PHP, and MySQL for subsequent requests of the same URL. It works by checking if a page is cached and either returning the cached version or passing the request to the backend server to handle and then cache the response. While it does not support SSL or user state directly, there are strategies like SSL termination, excluding certain pages, and using Edge Side Includes to handle dynamic content and user sessions. A case study showed Varnish improved response times from 500-800ms to under 100ms for a site with major traffic spikes.
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Speed up your site with Varnish
- 1. Speed up yoursite with Varnish PHP Cambridge, 21st March 2017 Simon Jones, Studio 24
- 2. Typical web applicationresponse Apache Database PHP Public internet Webserver Incoming web request Returning web response
- 3. • Can beslow • Each requests boots up Apache + PHP • Example memory footprint • 60MB per request • 100 concurrent users • = 6GB memory usage • Response time 300-900ms for a typical CMS application Problems
- 4. • CMS-level caching •E.g. cache content fragments to file / memcached • Still boots Apache, PHP and CMS application • Full-page caching • E.g. cache whole page to HTML • Faster, still boots Apache + PHP Caching options
- 6. Add Varnish Public internet Webserver Incoming webrequest (port 80) Returning web response Public internet Webserver Incoming web request (port 80) Returning web response Varnish Cache HTTP reverse proxy (port 8080)
- 7. How does Varnishwork? Public internet Webserver 1) Incoming web request (port 80) Varnish Cache Yes 4) Return HTTP response to user 3) Varnish returns page from memory 2) Varnish asks is this page cached? Public internet Webserver 1) Incoming web request (port 80) 6) Return HTTP response to user Varnish Cache 2) Varnish asks is this page cached? No 3) Pass through to webserver (port 8080) 4) Return HTTP response 5) Varnish caches page
- 8. • Caches HTTPresponse in memory • Skips Apache, PHP & MySQL • Each request for same URL = the same for all users (headers & contents) • Very, very fast How does Varnish work?
- 9. • Crossrail onstandard LAMP stack • Traffic spikes of 20,000 hits/day caused issues • Response time 500-800ms • Implemented Nginx + Varnish • Response time sub 100ms • Traffic peaks of 150,000 hits/day cause no issues Case study
- 10. • Use standardHTTP headers, Varnish will do the rest • Cache GET & HEAD only • Cache-Control: public, max-age=3600 • Cache-Control: private, no-cache, no-store HTTP responses
- 11. Downsides • Does notsupport SSL • Does not support unique user state (e.g. cookies)
- 12. • If POST,works fine • Exclude areas of your site (e.g. cart/*) • Use AJAX / JS / LocalStorage to manage functionality (e.g. Logged in message, cart contents) • Use Varnish ESI (Edge Side Includes) • Use Edgestash in Varnish Plus (mustache templates & JSON data) Strategies for dealing with state
- 13. Add SSL termination Publicinternet Webserver Incoming web request (port 443) Returning web response Varnish Cache HTTP reverse proxy After SSL termination (port 80) (port 8080)
- 14. • Hitch (TLSproxy) • Nginx (pass-thru requests) • Load balancer (terminates SSL) SSL termination options
- 15. Summary • Brilliant atdealing with high traffic spikes • Serves the same page for everyone • Use HTTP headers to control caching • Consider how to deal with unique content for users • SSL termination strategy
- 16. Resources • Varnish HTTPCache https://www.varnish-cache.org/ • Getting started with Varnish cache book https://info.varnish-software.com/getting-started-with-varnish-cache-oreilly-book • The Varnish book https://info.varnish-software.com/the-varnish-book • Hitch TLS proxy http://hitch-tls.org/
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