Introduction to Unicorn - Paul Grayson

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Transcript

1. Introduction to Unicorn, a Rack HTTP server Paul Grayson, 6 June 2012
2. Background - Rack • Rack is an interface between web servers and application code. • It is all Ruby: app is accessed via a method • Rails 3 is on Rack • [show example Rack app]
3. Background - sockets • HTTP connection life cycle 1.Server listens on a TCP port 2.Client connects 3.Server accepts the connection 4.HTTP Request/response etc.
4. Background - processes • Processes – Independent program copies – Copy-on-write saves RAM – Processes may share system resources ...such as sockets. Process 1 Process 2 sockets open files streams local variables execution state local variables execution state
5. Traditional Rack servers (Mongrel, Thin) • Multiple processes & ports • A proxy distributes clients 1 2 3 4
6. Traditional Rack servers (Mongrel, Thin) • Multiple processes & ports • A proxy distributes clients 1 2 3 4
7. Traditional Rack servers (Mongrel, Thin) • Multiple processes & ports • A proxy distributes clients 1 2 3 4
8. Traditional Rack servers (Mongrel, Thin) • Multiple processes & ports • A proxy distributes clients 1 2 3 4
9. Traditional Rack servers (Mongrel, Thin) Slow requests will slow down other clients! 1 2 3 4
10. Traditional Rack servers (Mongrel, Thin) Slow requests will slow down other clients! 2 3 4 1
11. Traditional Rack servers (Mongrel, Thin) Slow requests will slow down other clients! 2 4 1 3
12. [show thin example]
13. Unicorn • Multiple processes, ONE shared socket • Unicorns accept connections when idle 1 2 3 4 Next! Next!
14. Unicorn 1 3 4 2 • Multiple processes, ONE shared socket • Unicorns accept connections when idle
15. Unicorn 3 4 2 1 Next! • Multiple processes, ONE shared socket • Unicorns accept connections when idle
16. Unicorn 3 4 1 2 • Multiple processes, ONE shared socket • Unicorns accept connections when idle
17. Unicorn 4 2 1 3 Next! • Multiple processes, ONE shared socket • Unicorns accept connections when idle
18. Unicorn 4 1 2 3 • Multiple processes, ONE shared socket • Unicorns accept connections when idle
19. Unicorn 1 2 3 4 • Multiple processes, ONE shared socket • Unicorns accept connections when idle
20. [show unicorn example]
21. Unicorn – painless restarts with no downtime • Based on obscure UNIX signals: USR2: start new copy WINCH: gracefully stop workers QUIT: graceful shutdown – Lots of other signals, e.g. reopening logs • Write your own scripts to do it • [show example]
22. Unicorn does not solve all problems • Use something in front of ruby for – slow clients – static files • Unicorn will occasionally die, so monitor it (because it is Ruby?) • Rails still uses a lot of memory
23. 32-bit server, >200MB RAM per unicorn Conclusion: a decent server setup nginx buffering, static files unicorn unicorn unicorn unicorn monit, etc.