Servers with Event Machine - David Troy - RailsConf 2011
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EventMachine allows Ruby programs to handle many concurrent connections without blocking or threads. It uses an asynchronous model where callbacks are invoked in response to I/O events like incoming connections or data. EventMachine provides a high performance non-blocking TCP server that handles all I/O with callbacks rather than blocking. It can be used to build scalable I/O intensive applications like email servers that handle thousands of concurrent connections in a single Ruby process. The key is to never block the EventMachine reactor loop.
![require 'socket'
inbound server = TCPServer.new(2202)
list of clients clients = []
buffer per buffers = {}
client IO.select returns while true
sockets = [server] + clients
readable/writable readable, writable = IO.select(sockets)
sockets readable.each do |sock|
begin
if sock == server
clients << server.accept_nonblock
else
client, buf = sock, buffers[sock] ||= ''
read in available data,
buf << client.read_nonblock(1024)
process if full line received if buf =~ /^.+?r?n/
client.write "You said: #{buf}"
Non-Blocking I/O
client.close
buffers.delete(client)
clients.delete(client)
end
Alternative to end
rescue Errno::EAGAIN, Errno::EWOULDBLOCK
threads: simply don’t # socket would block, try again later
end
block end
end](https://image.slidesharecdn.com/serverswitheventmachine-davidtroy-railsconf2011-110526142302-phpapp02/85/Servers-with-Event-Machine-David-Troy-RailsConf-2011-14-320.jpg)
![EventMachine
Geo Firehose LISTEN
8192
(one connection - Port 80)
250, 500, 1000 Connections
twittervision.com/
Apache
stream
RewriteRule ^/stream(.*)$ http://127.0.0.1:8192%{REQUEST_URI} [P,QSA,L]](https://image.slidesharecdn.com/serverswitheventmachine-davidtroy-railsconf2011-110526142302-phpapp02/85/Servers-with-Event-Machine-David-Troy-RailsConf-2011-24-320.jpg)
Servers with Event Machine - David Troy - RailsConf 2011
- 1. Building Scalable Servers With EventMachine and Rails Dave Troy Chief Executive Officer [email protected] @davetroy facebook.com/davetroy
- 3. EventMachine
- 4. EventMachine DRY
- 5. EventMachine DRY DRAG
- 6. EventMachine DRY DRAG (Don’t Repeat Aman Gupta)
- 8. EventMachine scalable non-blocking i/o in ruby
- 9. About Me Aman Gupta San Francisco, CA Been maintaining EventMachine for 18 months (last 4 releases) Ruby Hero 2009 amqp, REE patches, perftools.rb, gdb.rb, memprof github.com/tmm1 @tmm1
- 10. What is EventMachine? Implementation of the Reactor pattern similar to Python’s Twisted also node.js, libev Ruby VM Support Ruby 1.8 (MRI) Ruby 1.9 (YARV) c++ reactor Rubinius JRuby java reactor + simple Pure Ruby version
- 11. What is I/O? Generally Network I/O mysql query responses http responses memcache results Most web applications are I/O bound, not CPU bound Basic idea behind EM: Instead of waiting on a response from the network, use that time to process other requests
- 12. What can I use EM for? Scaling I/O heavy applications handle 5-10k concurrent connections with a single ruby process Any type of network I/O http requests sending emails custom tcp proxies data access redis couchdb mysql postgres casandra memcached
- 13. Simple TCP Server TCPServer#accept require 'socket' server = TCPServer.new(2202) to accept while client = server.accept connections from msg = client.readline new clients client.write "You said: #{msg}" client.close TCPSocket#read* end blocks, so you can require 'socket' only handle one server = TCPServer.new(2202) client at a time while true Thread.new(server.accept){ |client| Common Solution: msg = client.readline client.write "You said: #{msg}" use a thread per client.close client } end
- 14. require 'socket' inbound server = TCPServer.new(2202) list of clients clients = [] buffer per buffers = {} client IO.select returns while true sockets = [server] + clients readable/writable readable, writable = IO.select(sockets) sockets readable.each do |sock| begin if sock == server clients << server.accept_nonblock else client, buf = sock, buffers[sock] ||= '' read in available data, buf << client.read_nonblock(1024) process if full line received if buf =~ /^.+?r?n/ client.write "You said: #{buf}" Non-Blocking I/O client.close buffers.delete(client) clients.delete(client) end Alternative to end rescue Errno::EAGAIN, Errno::EWOULDBLOCK threads: simply don’t # socket would block, try again later end block end end
- 15. EM does Non-Blocking I/O handles low module EchoServer level sockets def post_init for you @buf = '' end inbound/ def receive_data(data) @buf << data outbound if @buf =~ /^.+?r?n/ buffers for send_data "You said: #{@buf}" close_connection_after_writing maximal end throughput end end efficient i/o with writev/readv require 'eventmachine' EM.run do EM.start_server '0.0.0.0', 2202, EchoServer epoll & kqueue end support
- 16. So, what’s a Reactor? while reactor_running? expired_timers.each{ |timer| timer.process } new_network_io.each{ |io| io.process } end reactor is simply a single threaded while loop, called the “reactor loop” your code “reacts” to incoming events if your event handler takes too long, other events cannot fire lesson: never block the reactor while reactor_running? while true no sleep(1) end no long loops (100_000.times) # reactor is blocked! no blocking I/O (mysql queries) end no polling (while !condition)
- 17. Writing Asynchronous Code synchronous ruby code uses return values ret = operation() do_something_with(ret) evented async code uses blocks instead operation{ |ret| do_something_with(ret) } different from how you usually use ruby blocks. the block is stored and invoked later (it’s asynchronous) puts(1) puts(1) 1.times{ puts(2) } operation{ puts(3) } puts(3) puts(2)
- 18. Receiving Email Using ActionMailer port 25 postfix (smtp) (spool) fork process Action pgsql Mailer ActiveRecord (db)
- 19. Receiving Email Using LMTP port 25 postfix (smtp) (spool) port 8081 (lmtp) EM pgsql (w/Rails) ActiveRecord (db)
- 20. Receiving Email — Scalably via LMTP postfix postfix message (spool) (spool) systems EM EM EM EM (w/Rails) (w/Rails) (w/Rails) (w/Rails)
- 24. EventMachine Geo Firehose LISTEN 8192 (one connection - Port 80) 250, 500, 1000 Connections twittervision.com/ Apache stream RewriteRule ^/stream(.*)$ http://127.0.0.1:8192%{REQUEST_URI} [P,QSA,L]
- 25. replyz.com Does Anybody Know...? mailstrom.co mailstrom.410labs.com Power Tools for Your Inbox shortmail.com Email, simplified.
- 26. Some Other Handy Stuff... • start_tls: secure any TCP connection • Timers: Periodic, Once, Scheduled • epoll, kqueue, threadpool_size • set_effective_user (listen on protected ports) • teh docs: http://eventmachine.rubyforge.org/EventMachine.html
- 27. So, Some Stuff To Remember... • EventMachine: awesome for I/O, events • Code is Data, Data is Code • Often Working with State Machines • Don’t peg the CPU. No really, don’t. • TEBWTDI • Testing can be interesting
- 28. Dave Troy Chief Executive Officer [email protected] @davetroy facebook.com/davetroy Tomorrow @ BohConf! http://emrubyconf.com/