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Building high traffic http front-ends. theo schlossnagle. зал 1
- 1. High-performance Robust HTTP Front-ends / tips, tricks and expectations Saturday, April 23, 2011
- 2. Who am I? @postwait on twitter Author of “Scalable Internet Architectures” Pearson, ISBN: 067232699X Contributor to “Web Operations” O’Reilly, ISBN: Founder of OmniTI, Message Systems, Fontdeck, & Circonus I like to tackle problems that are “always on” and “always growing.” I am an Engineer A practitioner of academic computing. IEEE member and Senior ACM member. On the Editorial Board of ACM’s Queue magazine. 2 Saturday, April 23, 2011
- 3. Agenda • Why only HTTP? • HTTP-like protocols • Performance • Availability Saturday, April 23, 2011
- 4. HTTP • Why only HTTP... it’s what we do. • User-based, immediate, short-lived transactions occupy my life. • So, not just HTTP. • HTTPS • SPDY (... we’ll get to this) Saturday, April 23, 2011
- 5. Performance • ATS (Apache Traffic Server) • supports SSL • battle-hardened codebase • very multi-code capable • Varnish • VCL adds unparalleled flexibility • no SSL! • nginx • I don’t see much of this out on the edge Saturday, April 23, 2011
- 6. Performance Expectations • from a single server, you should be able to: • support 500k concurrent users • this is only 40k sockets/core • push in excess of 100k requests/second • this is only 9k requests/core*second • push close to 10 gigabits • this is why 10G was invented Saturday, April 23, 2011
- 7. Performance Achievements • Good load balancers achieve this performance • with dual socket Westmere processors, we’re able to achieve in software on general purpose hardware what was only possible in hardware ASICs. • ATS and Varnish can do this today. Saturday, April 23, 2011
- 8. The Basic Rules: Content • You must serve content from cache • Your cache should fit in memory • If it does not, it should spill to SSD, not spinning media. Saturday, April 23, 2011
- 9. The Basic Rules: CPU • You must cache SSL sessions • SSL key negotiation is expensive. • SSL encryption is not* • Common cases must not cause state on the firewall. • It’s hard enough to serve 150k requests/second. • You will spend too much time in kernel in iptables, ipf, or pf. • allow port 80 and port 443. • enable SYN flood prevention * crypto obviously costs CPU; symmetric crypto is relatively cheap Saturday, April 23, 2011
- 10. The Basic Rules: Network • You must not run a stateful firewall in front • too expensive • too little value • You must be directly behind capable router(s) • expect anywhere from 1MM to 20MM packets per second • we need to run BGP for availability Saturday, April 23, 2011
- 11. Availability • We learned in the performance section: • 1 machine / 10Gbps uplink performs well enough • We need redundancy: • Linux HA? • VRRP/HSRP? • CARP? • No... Saturday, April 23, 2011
- 12. Availability: Constraints • Client TCP sessions are relatively short lived. • The web is a largely idempotent place. • Clients are capable of retrying on failure. • This means: • forget stateful failover. • focus on availability for new connections. Saturday, April 23, 2011
- 13. Availability: Setup • You are behind a capable router (it was a rule) • Use routing protocols (BGP) to maintain availability. BGP 10.1.0.0/24 10.1.1.0/24 10.1.0.0/23 10.1.0.0/23 Saturday, April 23, 2011
- 14. Working Stacks • Linux (OS/TCP stack) • Illumos (OS/TCP stack) • Varnish (HTTP) • ATS (HTTP/HTTPS) • Quagga (BGP) • Quagga (BGP) Saturday, April 23, 2011
- 15. Future! • This stuff is fast. • In the end, we’re not looking for faster servers, we’re looking for improved user experience. • Enter SPDY • Google’s multi-channel HTTP super-protocol • Allows multiplexing of concurrent HTTP(like) request/response on a single TCP session. • Defeats slow startup • Allows for content prioritization on server Saturday, April 23, 2011
- 16. Future: my thoughts • SPDY is relatively simple to implement on the server • SPDY is very very hard to leverage on the server • If ATS implemented SPDY in and out • and provided a robust configuration language to leverage it ... the future would be today. Saturday, April 23, 2011
- 17. Thank you. • Thank you Олег Бунин • Thanks to the Varnish and ATS developers. • Спасибо. Saturday, April 23, 2011