meet a parallel, asynchronous php world
TRANSCRIPT
PHPDay 2015 – Verona, Italy, May 16th 2015
Meet a Parallel Asynchronous PHP World
STEVE @MARASPIN
http://www.mvlabs.it/
USE CASE
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AWESOME PHP MUM
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!
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!
GOING ENTERPRISE
TROUBLES ARISE
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~20s
WHY SO MUCH TIME?
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What do you want for lunch?
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What do you want for lunch?
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!
Solution #1: PHP Asynchronous Calls
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• Within PHP • Easy to use
Pros Cons
• Limited set of available commands
VARIETY WANTED
CHEFS TO THE RESCUE
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Simple Message Queue
Multiple Consumers / Workers
More Decoupling…
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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?
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
Solution #3: Job Server
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• Scales well • Decoupling • Possibly
resilient • Return Values
Pros Cons
• Extra software components
• Extra processes
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…
Solution #4: Exec & Co.
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• Very easy to implement
Pros Cons
• No return values
• Extra processes
PHP THREADS
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?
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
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
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
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
DIY TIMER
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
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
WHY A LOUSY OVEN?
WHEN WE COULD USE…
A REACTOR!
Reactor Pattern
event loop
(event1, callback1)
(event2, callback2)
on(event1) (callback1)
on(event2) (callback2)
Implements reactor pattern Formerly known as Node.PHP Non-blocking I/O Event Loop
http://reactphp.org
React
libev libevent
inotify epoll pol event ports kqueue select
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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
SUMMARIZING THINGS
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Parallel
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Asynchronous
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WHAT'S NEXT?
HACK ASYNC
http://docs.hhvm.com/manual/en/hack.async.php
Node.JS Galore
• https://github.com/chobie/php-uv
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Node.JS Galore
• https://github.com/JosephMoniz/node.php 199
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!
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 [email protected]