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PHPDay 2015 – Verona, Italy, May 16th 2015
Meet a Parallel
Asynchronous PHP World

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STEVE @MARASPIN

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http://www.mvlabs.it/

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USE CASE

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AWESOME PHP MUM

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How does it work?
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We have a client…
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What do you
want for lunch?

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Cool. BRB!

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PHP Makes I/O Requests…
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PHP awaits for I/O…
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I/O Ready
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Content Delivered
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DELICIOUS LUNCH!

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GOING ENTERPRISE

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TROUBLES ARISE

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~20s

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WHY SO MUCH TIME?

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What do you
want for lunch?

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What do you
want for lunch?

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Gotta look for
a better strategy…
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What do
you want for
lunch?

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What do
you want for
lunch?

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What do
you want for
lunch?

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curl_multi_add_handle

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curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

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curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

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curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

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~20s
~2s

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Ordered Results

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No More!

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Solution #1:
PHP Asynchronous Calls
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• Within PHP
• Easy to use
Pros Cons
• Limited set of
available
commands

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VARIETY WANTED

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CHEFS TO THE RESCUE

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Simple Message Queue

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Multiple Consumers / Workers

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More Decoupling…

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JACK OF ALL TRADES

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Useful if already within stack & simple system – please take a look: http://antirez.com/news/88

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lPush

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brPop

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batch_basic_publish / basic_publish

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basic_consume

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What do
you want for
lunch?

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What do
you want for
lunch?

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What do
you want for
lunch?

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?

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Solution #2:
Message Queues
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• Scales well
• Can be made
resilient
• Decoupling
Pros Cons
• Extra software
components
• Lack of Feedback
to invoking
process

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http://gearman.org/

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addTaskBackground

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addFunction

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addTaskBackground

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addTask

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~20s

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OK, so just
prepare …

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OK, so just
prepare …
We need multiple (parallel) workers if we wish to improve performance

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Solution #3:
Job Server
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• Scales well
• Decoupling
• Possibly
resilient
• Return Values
Pros Cons
• Extra
software
components
• Extra
processes

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PHP FAMILY BUSINESS

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What do
you want for
lunch?
What do
you want for
lunch?
What do
you want for
lunch?

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Background exec

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What do
you want for
lunch?

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?
?
?
Same problem as before…

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Solution #4:
Exec & Co.
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• Very easy to
implement
Pros Cons
• No return
values
• Extra
processes

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PHP THREADS

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pthreads
"pthreads requires a build of PHP
with ZTS (Zend Thread Safety)
enabled"
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pthreads
"pthreads requires a build of PHP
with ZTS (Zend Thread Safety)
enabled"
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MUM GOT DAUGHTER(S)

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pcntl_fork

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pcntl_waitpid

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What do
you want for
lunch?
What do
you want for
lunch?

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What do
you want for
lunch?

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Solution #5:
Forking processes
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• Within PHP
• Allows for
parallelism
• Exploits available
CPU cores
Pros Cons
• Feedback (besides exit
status) difficult to get
• Parallelism bound to #
of available CPU cores
• Not to be used within
Apache or web servers
in general

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Latency Comparison Numbers
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns
Mutex lock/unlock 25 ns
Main memory reference 100 ns
Send 1K bytes over 1 Gbps network 10,000 ns
Read 4K randomly from SSD* 150,000 ns
Read 1 MB sequentially from memory 250,000 ns
Round trip within same datacenter 500,000 ns
Read 1 MB sequentially from SSD* 1,000,000 ns
Disk seek 10,000,000 ns
Read 1 MB sequentially from disk 20,000,000 ns
Send packet CA->Netherlands->CA 150,000,000 ns
Let's consider these numbers…
Source: https://gist.github.com/jboner/2841832

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Latency Comparison Numbers
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns
Mutex lock/unlock 25 ns
Main memory reference 100 ns
Send 1K bytes over 1 Gbps network 10,000 ns
Read 4K randomly from SSD 150,000 ns
Read 1 MB sequentially from memory 250,000 ns
Round trip within same datacenter 500,000 ns
Read 1 MB sequentially from SSD 1,000,000 ns
Disk seek 10,000,000 ns
Read 1 MB sequentially from disk 20,000,000 ns
Send packet CA->Netherlands->CA 150,000,000 ns
We got an I/O issue!
Source: https://gist.github.com/jboner/2841832

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Blocking I/O happens when…
 Sending an e-mail
 Communicating with Databases
 Communicating with other
services
 Reading/writing data on Disk
 Reading/writing data on Network
 …

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What do
you want for
lunch?

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What do
you want for
lunch?

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What do
you want for
lunch?

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EVENTS

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DIY TIMER

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I/O Multiplexing
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PHP stream_select
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Runs the equivalent of the select() system call
on the given arrays of streams with a timeout
specified by tv_sec and tv_usec

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Solution #6:
stream_select
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• Within PHP
• Removes I/O
wait overhead
Pros Cons
• Cumbersome
within large
projects
• Performances
could be better

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Libevent
• API providing a mechanism to execute
a callback when a specific event
occurs on a file descriptor or after a
timeout
• supports /dev/poll, kqueue(2), event
ports, POSIX select(2), Windows
select(), poll(2), and epoll(4)
notification mechanisms
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Solution #7:
libevent
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• Within PHP
• More
performant
than select
Pros Cons
• Cumbersome
within large
projects
• Might behave
differently within
different OSs

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WHY A LOUSY OVEN?

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WHEN WE COULD USE…

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A REACTOR!

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Reactor Pattern

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event loop
(event1, callback1)
(event2, callback2)
on(event1)  (callback1)
on(event2)  (callback2)

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 Implements reactor pattern
 Formerly known as Node.PHP
 Non-blocking I/O
 Event Loop
http://reactphp.org

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React
libevlibevent
inotifyepollpolevent portskqueueselect

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Out of loop: Ignored!

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HTTP
Socket
Stream
Event Loop

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Promise

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Streams

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https://bugs.php.net/bug.php?id=64696
"epoll" itself (used by Libevent on Linux)
doesn't support regular files. Epoll expects
whether sockets, or pipes"

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Libev uninstalled…

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Solution #8:
React
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• Wrapper
around many
event handlers
• Good
abstractions
Pros Cons
• Still in 0.x
• New
paradigm

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SUMMARIZING THINGS

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Parallel

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Asynchronous

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WHAT'S NEXT?

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HACK ASYNC
http://docs.hhvm.com/manual/en/hack.async.php

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Node.JS Galore
• https://github.com/chobie/php-uv
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Node.JS Galore
• https://github.com/JosephMoniz/node.php
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Interesting resources…
• Ratchet
http://socketo.me/
• Cooperative Multitasking using coroutines
https://nikic.github.io/2012/12/22/Cooperative-
multitasking-using-coroutines-in-PHP.html
• Recoil
https://github.com/recoilphp/recoil
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THANK YOU!

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Picture Credits
Spider: https://www.flickr.com/photos/janajermakova/10616495683/
Table: https://www.flickr.com/photos/turnstonefurniture/5731379672/
Gnocchi: https://www.flickr.com/photos/cookingetc/6864270056/
Skeptical Dog: https://www.flickr.com/photos/jacobyarborough/13564967155/
Kitchen Accident: https://www.flickr.com/photos/aleksiaaltonen/4803518904/
Variety: https://www.flickr.com/photos/gammaman/6135388116/
Chefs: https://www.flickr.com/photos/lesroches/8700412835/
Man in Kitchen: https://www.flickr.com/photos/paullew/4542993694/
Family: https://www.flickr.com/photos/gareth1953/5173076989/
Organize: https://www.flickr.com/photos/7502393@N04/472028888/
Timer: https://www.flickr.com/photos/lucidscience/5079439604/
Oven: https://www.flickr.com/photos/bonedaddy/2889601088
Presentation: https://www.flickr.com/photos/oecd_development_centre/10168550803/
Reactor: https://www.flickr.com/photos/mandj98/2468396121/
Stirring: https://www.flickr.com/photos/nicoleabalde/7191104180/
Table Ready: https://www.flickr.com/photos/thefalcondale/6940598837/
Other pictures by Steve Maraspin, or from Fotolia Archives
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Stefano Maraspin
@maraspin
s.maraspin@mvlabs.it