Steve Maraspin gave a presentation on asynchronous and parallel PHP. He began by demonstrating how blocking I/O calls can slow down PHP applications and presented several approaches to address this issue including asynchronous calls, message queues, job servers, forking processes, stream_select, libevent, and React. He discussed the pros and cons of each approach and provided code examples. He concluded by discussing additional asynchronous options for PHP like Hack and Node.js and thanked the audience.

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

2. STEVE @MARASPIN

4. http://www.mvlabs.it/

5. USE CASE

6. 6

7. 7

8. AWESOME PHP MUM

9. How does it work?
9

10. We have a client…
10

11. 11
What do you
want for lunch?

12. 12

13. 13
Cool. BRB!

14. PHP Makes I/O Requests…
14

15. PHP awaits for I/O…
15

16. I/O Ready
16

17. Content Delivered
17

18. DELICIOUS LUNCH!

19. GOING ENTERPRISE

20. TROUBLES ARISE

21. 21

22. 22

23. 23
~20s

24. WHY SO MUCH TIME?

25. 25

26. 26

27. 27

28. 28

29. 29

30. 30

31. 31
What do you
want for lunch?

32. 32

33. 33

34. 34

35. 35
What do you
want for lunch?

37. Gotta look for
a better strategy…
37

38. 38
What do
you want for
lunch?

39. 39
What do
you want for
lunch?

40. 40
What do
you want for
lunch?

41. 41

42. 42

43. 43

44. 44

45. 45

46. 46

47. 47

48. 48

49. 49
curl_multi_add_handle

50. 50
curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

51. 51
curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

52. 52
curl_multi_exec
curl_multi_info_read
curl_multi_getcontent

53. 53

54. 54
~20s
~2s

55. 55
Ordered Results

56. 56
No More!

57. Solution #1:
PHP Asynchronous Calls
57

58. 58
• Within PHP
• Easy to use
Pros Cons
• Limited set of
available
commands

59. VARIETY WANTED

60. CHEFS TO THE RESCUE

61. 61

62. Simple Message Queue

63. Multiple Consumers / Workers

64. More Decoupling…

65. JACK OF ALL TRADES

66. 66
Useful if already within stack & simple system – please take a look: http://antirez.com/news/88

67. 67

68. 68
lPush

69. 69
brPop

70. 70

71. 71

72. 72
batch_basic_publish / basic_publish

73. 73
basic_consume

74. 74

75. 75
What do
you want for
lunch?

76. 76
What do
you want for
lunch?

77. 77
What do
you want for
lunch?

78. 78

79. 79

80. 80

81. 81

82. 82
?

83. Solution #2:
Message Queues
83

84. 84
• Scales well
• Can be made
resilient
• Decoupling
Pros Cons
• Extra software
components
• Lack of Feedback
to invoking
process

85. 85

86. 86
http://gearman.org/

87. 87
addTaskBackground

88. 88
addFunction

89. 89

90. 90
addTaskBackground

91. 91
addTask

92. 92

93. 93
~20s

94. 94
OK, so just
prepare …

95. 95

96. 96

97. 97

98. 98

99. 99

100. 100

101. 101

102. 102

103. 103
OK, so just
prepare …
We need multiple (parallel) workers if we wish to improve performance

104. Solution #3:
Job Server
104

105. 105
• Scales well
• Decoupling
• Possibly
resilient
• Return Values
Pros Cons
• Extra
software
components
• Extra
processes

106. PHP FAMILY BUSINESS

107. 107
What do
you want for
lunch?
What do
you want for
lunch?
What do
you want for
lunch?

108. 108

109. 109

110. 110

111. 111

112. 112
Background exec

113. 113

114. 114
What do
you want for
lunch?

115. 115
?
?
?
Same problem as before…

116. Solution #4:
Exec & Co.
116

117. 117
• Very easy to
implement
Pros Cons
• No return
values
• Extra
processes

118. PHP THREADS

119. pthreads
"pthreads requires a build of PHP
with ZTS (Zend Thread Safety)
enabled"
119

120. pthreads
"pthreads requires a build of PHP
with ZTS (Zend Thread Safety)
enabled"
120

121. MUM GOT DAUGHTER(S)

122. 122

123. 123
pcntl_fork

124. 124
pcntl_waitpid

125. 125

126. 126
What do
you want for
lunch?
What do
you want for
lunch?

127. 127

128. 128

129. 129
What do
you want for
lunch?

130. Solution #5:
Forking processes
130

131. 131
• 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

132. 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

133. 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

134. 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
 …

136. 136
What do
you want for
lunch?

137. 137

138. 138
What do
you want for
lunch?

139. 139

140. 140
What do
you want for
lunch?

141. 141

142. 142

143. 143

144. 144

145. 145

146. 146

147. 147

148. 148

149. 149

150. 150

151. EVENTS

153. DIY TIMER

154. I/O Multiplexing
154

156. PHP stream_select
156
Runs the equivalent of the select() system call
on the given arrays of streams with a timeout
specified by tv_sec and tv_usec

157. 157

158. 158

159. 159

160. Solution #6:
stream_select
160

161. 161
• Within PHP
• Removes I/O
wait overhead
Pros Cons
• Cumbersome
within large
projects
• Performances
could be better

162. 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
162

163. 163

164. 164

165. Solution #7:
libevent
165

166. 166
• Within PHP
• More
performant
than select
Pros Cons
• Cumbersome
within large
projects
• Might behave
differently within
different OSs

167. WHY A LOUSY OVEN?

168. WHEN WE COULD USE…

169. A REACTOR!

170. Reactor Pattern

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

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

174. React
libevlibevent
inotifyepollpolevent portskqueueselect

175. 175

176. 176
Out of loop: Ignored!

177. 177

178. HTTP
Socket
Stream
Event Loop

179. 179

180. 180
Promise

181. 181

182. 182
Streams

183. 183

184. 184

185. 185
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"

186. 186
Libev uninstalled…

187. 187

188. 188

189. 189

190. Solution #8:
React
190

191. 191
• Wrapper
around many
event handlers
• Good
abstractions
Pros Cons
• Still in 0.x
• New
paradigm

192. SUMMARIZING THINGS

193. 193
Parallel

194. 194
Asynchronous

195. 195

196. WHAT'S NEXT?

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

198. Node.JS Galore
• https://github.com/chobie/php-uv
198

199. Node.JS Galore
• https://github.com/JosephMoniz/node.php
199

200. 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
200

201. THANK YOU!

202. 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
202

203. Stefano Maraspin
@maraspin
s.maraspin@mvlabs.it