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Rails Four &
The Future!
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Rails Four
For you and for me!
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Aaron Patterson
@tenderlove
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HI!! :-)
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AT&T, AT&T logo and all AT&T related marks are trademarks of AT&T Intellectual Property and/or AT&T affiliated companies.
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Aloha Ruby Conference
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SPAM!!!
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Dog the Bounty Hunter
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Magnum P.I.
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Proof!
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WWFMD
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No content
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Gorbachev
Puff-Puff
Thunderhorse
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No content
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No content
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No content
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No content
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@gorbypuff
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Rails Four
For you and me!!!
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The Web!
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Not a TV Psychic
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Ruby
Rails
Web
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Concurrency
In Ruby
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Parallelization
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P56N
(possibly misspelled)
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GIL
Global Interpreter Lock
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Alternatives:
JRuby / Rubinius
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Good News!
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GIL was removed!
In Ruby 1.9
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Bad News.
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GIL was replaced
with GVL
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Is MRI useless?
For P32N
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def fib(n)
if n < 3
1
else
fib(n-1) + fib(n-2)
end
end
4.times { fib(34) }
Recursive Fib()
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[aaron@higgins git]$ time ruby test.rb
real 0m5.727s
user 0m5.706s
sys 0m0.011s
[aaron@higgins git]$
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def fib(n)
if n < 3
1
else
fib(n-1) + fib(n-2)
end
end
4.times.map {
Thread.new { fib(34) }
}.each(&:join)
Threaded Fib()
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[aaron@higgins git]$ time ruby test.rb
real 0m5.753s
user 0m5.732s
sys 0m0.014s
[aaron@higgins git]$
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❤ Use JRuby or Rubinius
❤ Use multiple processes
What do we do?
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Slow Server
server = WEBrick::GenericServer.new(:Port => 28561,
:MaxClients => 4)
server.start do |socket|
{ } until socket.gets == "\r\n"
socket.print "HTTP/1.0 200 OK\r\n"
socket.print "\r\n"
sleep 0.5
socket.print "Hello World"
socket.close
end
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Slow Server
server = WEBrick::GenericServer.new(:Port => 28561,
:MaxClients => 4)
server.start do |socket|
{ } until socket.gets == "\r\n"
socket.print "HTTP/1.0 200 OK\r\n"
socket.print "\r\n"
sleep 0.5
socket.print "Hello World"
socket.close
end
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Client
require 'net/http'
uri = URI('http://localhost:28561')
4.times {
puts Net::HTTP.get_response uri
}
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$ time ruby client.rb
Hello World
Hello World
Hello World
Hello World
real 0m2.029s
user 0m0.017s
sys 0m0.012s
$
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$ time ruby client.rb
Hello World
Hello World
Hello World
Hello World
real 0m2.029s
user 0m0.017s
sys 0m0.012s
$
4 * 0.5
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require 'net/http'
uri = URI('http://localhost:28561')
4.times.map {
Thread.new {
puts Net::HTTP.get_response(uri).body
}
}.each &:join
Threaded Client
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$ time ruby client.rb
Hello World
Hello World
Hello World
Hello World
real 0m0.525s
user 0m0.016s
sys 0m0.009s
$
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$ time ruby client.rb
Hello World
Hello World
Hello World
Hello World
real 0m0.525s
user 0m0.016s
sys 0m0.009s
$
0.525!
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❤ Release GVL
❤ Wait until data is ready (select())
❤ Acquire GVL
IO#read
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rb_thread_blocking_region()
GVL Magic
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What does it
mean?
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Fibonacci
As A Service
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FAAS
(the next big thing)
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A Blocked VM is a
Blocked VM
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Threads Matter
Even with a GVL
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Thread Safety
In Rails
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Delete
config.threadsafe!
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Why delete?
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Always be
thread safe!
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Always be
thread safe!
My
Opinion!
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Simplify
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Is it safe to
remove?
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What did it do?
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threadsafe!
❤ Preload frameworks (enable)
❤ Cache classes (enable)
❤ Dependency loading (disable)
❤ Allow concurrency (enable)
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Loading Code isn’t
Thread-safe*
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Preload
Frameworks
EN
A
B
LED
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Cache classes
EN
A
B
LED
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Dependency
Loading
D
ISA
B
LED
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Allow Concurrency
EN
A
B
LED
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Get Lock
Read from Socket
Process Stuff
Write to Socket
Release Lock
Rack::Lock
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Thread 2 Get Lock
Read from Socket
Process Stuff
Write to Socket
Release Lock
Thread 1
Rack::Lock
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Thread 2 Get Lock
Read from Socket
Process Stuff
Write to Socket
Release Lock
Rack::Lock
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Thread 2
Get Lock
Read from Socket
Process Stuff
Write to Socket
Release Lock
Rack::Lock
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Rack::Lock with
Processes
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Rack::Lock with
Threads
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Best Case:
Extra Overhead
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Worst Case:
1 req at a time
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IMPACT
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Boot time
increases (in prod)
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Fewer middleware
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Multi-Proc servers
stay the same
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Threaded servers
Just Work™
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Bug Fixes
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100% Caching
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Locking ||=
def some_method
@value ||= some_calculation
end
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check then act
Is nil?
Calculate
Return
Set
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check then act
Is nil?
Calculate
Return
Thread 1
Set
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check then act
Is nil?
Calculate
Return
Thread 1
Set
Thread 2
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check then act
Is nil?
Calculate
Return
Thread 1 Set
Thread 2
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check then act
Is nil?
Calculate
Return
Set
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Fix #1 (eager init)
class Foo
class << self
def hard_calculation
@calc
end
end
@calc = fib(34)
end
p Foo.hard_calculation
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Fix #2 (locking)
class Foo
@lock = Mutex.new
class << self
def hard_calculation
@lock.synchronize do
@calc ||= fib(34)
end
end
end
end
p Foo.hard_calculation
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Fix #2 (locking)
class Foo
@lock = Mutex.new
class << self
def hard_calculation
@lock.synchronize do
@calc ||= fib(34)
end
end
end
end
p Foo.hard_calculation
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Fix #2 (locking)
class Foo
@lock = Mutex.new
class << self
def hard_calculation
@lock.synchronize do
@calc ||= fib(34)
end
end
end
end
p Foo.hard_calculation
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Move methods to
instances
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Move to object
class Foo
def initialize
@calc = fib(34)
end
def hard_calculation
@calc
end
end
Foo.new.hard_calculation
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Lazy Object
class Foo
include Mutex_m
def hard_calculation
synchronize do
@calc ||= fib(34)
end
end
end
Foo.new.hard_calculation
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Maintain API
class Foo
include Mutex_m
def hard_calculation
synchronize do
@calc ||= fib(34)
end
end
Instance = new
def self.hard_calculation
Instance.hard_calculation
end
end
Foo.hard_calculation
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Hash.new { }
class Foo
def initialize
@cache = Hash.new { |h,k|
h[k] = []
}
end
def some_value(key)
@cache[key]
end
end
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Fix #1 (lock)
class Foo
include Mutex_m
def initialize
super
@cache = Hash.new { |h,k|
h[k] = []
}
end
def some_value(key)
synchronize { @cache[key] }
end
end
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Fix #2 thread_safe
https://github.com/headius/thread_safe
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What about the
App Level?
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Thread Safety
In Web Apps
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Avoid shared data
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Most people don’t
type “Thread.new”
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Look for things
that are global.
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Global Variables
$so_global = {}
$so_global[:foo] ||= “bar”
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Constants
SET_TWICE = 10
SET_TWICE = 10
ALSO_GLOBAL = {}
ALSO_GLOBAL[:foo] ||= “bar”
Warning
No Warning
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Class methods
class MyModel
def self.some_cache
@foo ||= fib(34)
end
end
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Avoid global data
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Add locks
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Streaming
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Template
Rendering Today
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Templates Results
are Buffered
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Clients are blocked
while Rails works
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The entire page
must fit in memory
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Rack Encourages
Buffering
class MyApplication
def call(env)
[200, {}, [‘my page’]]
end
end
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We can do I/O and
CPU in parallel.
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So why buffer?
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ActionController::Live
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Example
class BrowserController < ApplicationController
include ActionController::Live
def index
100.times do
response.stream.write "hello!\n"
end
response.stream.close
end
end
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Example
class BrowserController < ApplicationController
include ActionController::Live
def index
100.times do
response.stream.write "hello!\n"
end
response.stream.close
end
end
Mix in
Stream
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response.stream
acts like
an I/O object
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Everything
Is a File
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How does it work?
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Our API
def index
response.status = 200
response.headers[‘X-Whatever’] = ‘<3’
response.stream.write ‘hello’
response.stream.write ‘ world’
response.stream.close
end
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Rack API
def call(env)
return [200,
{‘X-Whatever’ => ‘<3’},
[‘hello world’]]
end
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Wrapped Request
class Response
attr_accessor :status
attr_reader :headers, :stream
def initialize
@status = 200
@headers = {}
@stream = StringIO.new
end
end
def call(env)
res = Response.new
controller.response = res
controller.index
[res.status, res.headers, res.stream]
end
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Threaded action
def call(env)
res = Response.new
controller.response = res
Thread.new { controller.index }
[res.status, res.headers, res.stream]
end
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Block until write
def call(env)
res = Response.new
controller.response = res
Thread.new { controller.index }
res.stream.await
[res.status, res.headers, res.stream]
end
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Block until write
def call(env)
res = Response.new
controller.response = res
Thread.new { controller.index }
res.stream.await
[res.status, res.headers, res.stream]
end
Block
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Blocking Buffer
class Buffer
def initialize
@latch = Latch.new
@buffer = Queue.new
end
def await # wait for write
@latch.await
end
def write(str)
@latch.release
@buffer << str
end
end
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Blocking Buffer
class Buffer
def initialize
@latch = Latch.new
@buffer = Queue.new
end
def await # wait for write
@latch.await
end
def write(str)
@latch.release
@buffer << str
end
end
`call` blocks here
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Blocking Buffer
class Buffer
def initialize
@latch = Latch.new
@buffer = Queue.new
end
def await # wait for write
@latch.await
end
def write(str)
@latch.release
@buffer << str
end
end
`write` unblocks
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What can we do?
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Rails Internals
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Streaming ERB
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View Source
# encoding: utf-8
require 'erb'
doc = ERB.new '<%= hello %> world'
puts doc.src
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Source
#coding:UTF-8
_erbout = '';
_erbout.concat(( hello ).to_s);
_erbout.concat " world";
_erbout.force_encoding(__ENCODING__)
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Control Output
class MyERB < ERB
def set_eoutvar(compiler, eoutvar = '_erbout')
compiler.put_cmd = "#{eoutvar}.write"
compiler.insert_cmd = "#{eoutvar}.write"
compiler.pre_cmd = []
compiler.post_cmd = []
end
end
doc = MyERB.new '<%= hello %> world', nil, nil, '$stdout'
puts doc.src
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Source
#coding:UTF-8
$stdout.write(( hello ).to_s);
$stdout.write " world"
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$ ruby test.rb
hello world
$
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Web Apps
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Infinite Streams
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Server Sent Events
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SSE Response
HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Type: text/event-stream
Transfer-Encoding: chunked
event: ping
data: {"ping":"2012-10-06T21:44:41-07:00"}
event: reload
data: {"changed":["/Users/aaron/git/lolwut/app/views/
users/"]}
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SSE Response
HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Type: text/event-stream
Transfer-Encoding: chunked
event: ping
data: {"ping":"2012-10-06T21:44:41-07:00"}
event: reload
data: {"changed":["/Users/aaron/git/lolwut/app/views/
users/"]}
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SSE Response
HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Type: text/event-stream
Transfer-Encoding: chunked
event: ping
data: {"ping":"2012-10-06T21:44:41-07:00"}
event: reload
data: {"changed":["/Users/aaron/git/lolwut/app/views/
users/"]}
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SSE Response
HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Type: text/event-stream
Transfer-Encoding: chunked
event: ping
data: {"ping":"2012-10-06T21:44:41-07:00"}
event: reload
data: {"changed":["/Users/aaron/git/lolwut/app/views/
users/"]}
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Client Side
jQuery(document).ready(function() {
setTimeout(function() {
var source = new EventSource('/control');
// if we get a reload command, reload the page
source.addEventListener('reload', function(e) {
window.location.reload();
});
}, 1);
});
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Client Side
jQuery(document).ready(function() {
setTimeout(function() {
var source = new EventSource('/control');
// if we get a reload command, reload the page
source.addEventListener('reload', function(e) {
window.location.reload();
});
}, 1);
});
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Client Side
jQuery(document).ready(function() {
setTimeout(function() {
var source = new EventSource('/control');
// if we get a reload command, reload the page
source.addEventListener('reload', function(e) {
window.location.reload();
});
}, 1);
});
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Client Side
jQuery(document).ready(function() {
setTimeout(function() {
var source = new EventSource('/control');
// if we get a reload command, reload the page
source.addEventListener('reload', function(e) {
window.location.reload();
});
}, 1);
});
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Real-Time Browser
Communication
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Puma
Browser
FS-Events
FS Events
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Puma
Browser
FS-Events
FS Events
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Puma
Browser
FS-Events
FS Events
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Puma
Browser
FS-Events
FS Events
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Puma
Browser
Console
DRB
DB Events
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Puma
Browser
Console
DRB
DB Events
Socket
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Other Input Sources
❤ Embedded systems (sausage box)
❤ Telephony (twilio)
❤ Other users (chat systems)
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Thread Safety
P72N
Streaming
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Cores are
increasing.
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We need to utilize
the entire machine
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High latency clients
are increasing.
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Patience is
decreasing.
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Lie.
Using cached data
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Cheat.
Updating partial parts of the page
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Steal.
Move computations to client side via JS
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Lie.
Cheat.
Steal.
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Be Good
Engineers
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THANK YOU
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Questions?