1 hour dive into Erlang/OTP

1. 1 hour dive into Erlang/OTP @jvalduvieco @jordillonch

2. Problem domain

3. Lots of users

4. Lots of users

5. 24x7x365

6. 24x7x365

7. Lots of critical concurrent transactions

8. Lots of critical concurrent transactions

9. Hardware or software breaks

10. Hardware or software breaks

11. Lots of code changes

12. Lots of code changes

13. Unscalable Unmaintainable } code

14. Unscalable Unmaintainable } code

15. Maintenance/Debug in production system

16. Maintenance/Debug in production system

17. Does it sound to you?

18. The Erlang solution

19. Simplicity...

20. Minimize defensive programming

21. Typeless variables

22. Develop by contract

23. t-shirt function size If

25. function

26. does

27. not

28. fit

29. on

30. your

31. t-shirt

32. it

33. is

34. too

35. long!

36. Single responsibility principle

37. No shared state between entities

38. High Concurrency

39. High Concurrency High concurrency

40. Light threads

41. Light threads hundreds of thousands of threads in one machine with a good cpu scheduler

42. Light threads hundreds of thousands of threads in one machine with a good cpu scheduler Lt Lt Lt

43. Message passing Lt Lt Lt

44. Message passing A shared nothing architecture that communicates through message passing Lt Lt Lt

45. Message passing A shared nothing architecture that communicates through message passing Lt Lt Lt

46. Process Mailbox Lt Lt Lt

47. Process Mailbox Every process has a mailbox with incoming messages, process take on convenience Lt Lt Lt

48. No shared state Lt S Lt S Lt S

49. No shared state Every process its own internal state stored in a variable avoiding lock contention Lt S Lt S Lt S

50. Soft realtime

51. Soft realtime You have no strict guarantees on latency but language is designed to have low latency

52. High availability

53. High availability High availability

54. Supervised processes Pa Pb

55. Supervised processes processes can be monitored by other processes, handling its termination Pa Pb

56. Fail early Pa Pb S

57. Fail early Fail as soon as possible and let someone handle bad data, someone will restart you Pa Pb S

58. Fail early Fail as soon as possible and let someone handle bad data, someone will restart you Pa Pb2 S

59. Hot code update Pb Pa v1 S Pc

60. Hot code update processes code and data can be replaced without loosing service Pb Pa v1 S Pc

61. Hot code update processes code and data can be replaced without loosing service Pb Pa v1 v2 S Pc

62. Distribution Node Node P P P P P P P P P P P P

63. Distribution Processes run on nodes and can be located wherever they are Node Node P P P P P P P P P P P P

64. How does it look like?

66. Show me the code!

67. Demo 1

68. Hands on

69. The shell

70. Type on your console: erl

71. You should see: Erlang R16B (erts-5.10.1) [source] [64-bit] [smp:2:2] [async-threads:10] [hipe] [kernel- poll:false] [dtrace] Eshell V5.10.1 (abort with ^G) 1

72. Variables

73. Variables start Uppercase

74. Variables are immutable

75. Can contain any type

76. You can do things like...

77. 1 Foo = 1. 1 2 Foo = 2. ** exception error: no match of right hand side value 2

78. Foo

79. is

80. bounded

81. to

82. 1 1 Foo = 1. 1 2 Foo = 2. ** exception error: no match of right hand side value 2

83. Foo

84. is

85. bounded

86. to

87. 1 1 Foo = 1. 1 Foo

88. ==

90. ? 2 Foo = 2. ** exception error: no match of right hand side value 2

91. 1 Foo = 1. 1 2 Bar = 2. 2 3 Foo = Bar. ** exception error: no match of right hand side value 2

92. This is GREAT!

93. Now you have your basic error checking system implemented

94. Advanced types

95. [List]

96. [1,2,3,4,5,6]

98. Iterate sequentially

99. 1 MyList = [1,2,3,4]. [1,2,3,4] 2 [Head|Tail] = MyList. [1,2,3,4] 3 Head. 1 4 Tail. [2,3,4]

102. Do something to all or some items on a list (list comprehensions)

103. 1 MyList = [1, 2, 3, 4]. [1,2,3,4] 2 [X + 2 || X - MyList, X 2]. [5,6]

104. [Strings]

105. A list

107. 1 MyString = Erlang is not Ruby. Erlang is not Ruby

108. 1 MyString = Erlang is not Ruby. Erlang is not Ruby 2 [Head2|Tail2] = MyString. Erlang is not Ruby 3 Head2. 69 ASC

109. =

110. “E” 4 Tail2. rlang is not Ruby

111. {Tuples}

112. {1,2,3}

113. Basic data container

114. random access

115. matcheable

117. 1 Mytuple = {1,2,3,4}. {1,2,3,4} 2 A = 1. 1 3 B = 2. 2 4 {A,B,C,D} = {1,2,3,4}. {1,2,3,4} 5 C. 3 6 D. 4

118. 1 Mytuple = {1,2,3,4}. {1,2,3,4} 2 A = 1. 1 A

119. and

120. B

121. are 3 B = 2. bounded

122. variables 2 4 {A,B,C,D} = {1,2,3,4}. {1,2,3,4} 5 C. 3 6 D. 4

123. 1 Mytuple = {1,2,3,4}. {1,2,3,4} 2 A = 1. 1 A

124. and

125. B

127. variables 2 4 {A,B,C,D} = {1,2,3,4}. {1,2,3,4} 5 C. pattern

128. matching 3 A==1? 6 D. B==2? 4

129. 1 Mytuple = {1,2,3,4}. {1,2,3,4} 2 A = 1. 1 A

130. and

131. B

133. variables 2 4 {A,B,C,D} = {1,2,3,4}. C

134. and

135. D

136. are

137. {1,2,3,4} unbounded

138. 5 C. pattern

139. matching variables 3 A==1? 6 D. B==2? 4

140. functions

141. functions are types

142. single exit point

144. foo_bar_func(Foo, Bar) - Result = Foo + Bar, Result.

145. This

146. is

147. a

148. arity

149. 2

150. function

151. (2

152. parameters) foo_bar_func(Foo, Bar) - Result = Foo + Bar, Result.

153. This

154. is

155. a

156. arity

157. 2

158. function

159. (2

160. parameters) foo_bar_func(Foo, Bar) - Result = Foo + Bar, Result. means

161. that

162. more

163. code

164. is

165. to

166. come

167. This

168. is

169. a

170. arity

171. 2

172. function

173. (2

175. that

176. more

177. code

178. is

179. to

180. come means

181. the

182. function

183. code

184. has

185. ended

186. This

187. is

188. a

189. arity

190. 2

191. function

192. (2

194. that

195. more

196. code

197. is

198. to

199. come Single

200. exit

201. point Returns

202. Result means

203. the

204. function

205. code

206. has

207. ended

208. 1 FooBar = fun(Foo, Bar) - 1 Foo + Bar 1 end. #Funerl_eval.12.82930912 2 Result = FooBar(1, 2). 3

209. atoms

210. A constant with name

211. lowercase

213. 1 ok. ok 2 ko. ko 3 ok =:= ko. false 4 ok =:= ok. true

214. 1 MyFuncOK = fun() - {ok, 33} end. #Funerl_eval.20.82930912 2 MyFuncFail = fun() - {error, bad_arg} end. #Funerl_eval.20.82930912 3 {ok, Result} = MyFuncOK(). {ok,33} 4 {ok, Result2} = MyFuncFail(). ** exception error: no match of right hand side value {error,bad_arg}

215. atoms 1 MyFuncOK = fun() - {ok, 33} end. #Funerl_eval.20.82930912 2 MyFuncFail = fun() - {error, bad_arg} end. #Funerl_eval.20.82930912 3 {ok, Result} = MyFuncOK(). {ok,33} 4 {ok, Result2} = MyFuncFail(). ** exception error: no match of right hand side value {error,bad_arg}

216. atoms 1 MyFuncOK = fun() - {ok, 33} end. #Funerl_eval.20.82930912 2 MyFuncFail = fun() - {error, bad_arg} end. #Funerl_eval.20.82930912 } 3 {ok, Result} = MyFuncOK(). {ok,33} error 4 {ok, Result2} = MyFuncFail(). checking ** exception error: no match of right hand side value {error,bad_arg}

217. atoms 1 MyFuncOK = fun() - {ok, 33} end. #Funerl_eval.20.82930912 2 MyFuncFail = fun() - {error, bad_arg} end. #Funerl_eval.20.82930912 } 3 {ok, Result} = MyFuncOK(). {ok,33} error 4 {ok, Result2} = MyFuncFail(). checking ** exception error: no match of right hand side value {error,bad_arg} do

218. they

219. match?

220. modules

221. basic name spacing

222. public/private functions

224. On your ${EDITOR} create cool_func.erl -module(cool_func). -export([foo_bar_func/2]). foo_bar_func (Foo, Bar) - Result = Foo + Bar, {ok, Result}.

225. On erlang shell type: 1 c(cool_module). {ok,cool_module} 2 {ok, Result3} = cool_module:sum(33, 44). {ok,77} 3 Result3. 77

226. Too easy? Let’s add some pattern matching on parameters!

227. area({square, Side}) - {ok,Side * Side}; area({circle, Radius}) - % almost :-) {ok, 3 * Radius * Radius}; area({triangle, A, B, C}) - S = (A + B + C)/2, {ok, math:sqrt(S*(S-A)*(S-B)*(S-C))}; area(Other) - {error, invalid_object}.

228. area({square, Side}) - {ok,Side * Side}; means

229. that

230. there

231. is

232. area({circle, Radius}) - another

233. matching

234. % almost :-) posibility {ok, 3 * Radius * Radius}; area({triangle, A, B, C}) - S = (A + B + C)/2, {ok, math:sqrt(S*(S-A)*(S-B)*(S-C))}; area(Other) - {error, invalid_object}.

235. area({square, Side}) - {ok,Side * Side}; means

236. that

237. there

238. is

239. area({circle, Radius}) - another

240. matching

241. % almost :-) posibility {ok, 3 * Radius * Radius}; area({triangle, A, B, C}) - S = (A + B + C)/2, {ok, math:sqrt(S*(S-A)*(S-B)*(S-C))}; area(Other) - {error, invalid_object}. mymodule:area({square, 10}). mymodule:area({circle, 10}). mymodule:area({triangle, 2, 2, 3.5}).

242. Want more? Let’s add some recursion!

243. Want more? Let’s add some recursion! Erlang does not use loops

244. factorial(0) - 1; factorial(N) - N * factorial(N-1).

245. OTP

246. Oh, This is Perfect!

247. OTP is a set of rock solid architecture patterns, practices and tools

248. Improves the design, fault tolerance and deployment of your app

249. Erlang is just a language, OTP makes it great for the real world

251. Basic architecture patterns

252. Supervisor S P P P S P P

253. Supervisor S P P P S P P

254. Supervisor spawns processes and handles its death

255. gen_server P P gs P

256. gen_server P P gs P

257. Generic single threaded server

258. gen_fsm P P gf{S} P

259. gen_fsm P P gf{S} P

260. Generic Finite State Machine

261. gen_event P P P em P P P

262. gen_event P P P em P P P

263. Event handler, you can subscribe to events

264. More on OTP... • File hierarchy • Applications • Releases • Basic abstraction libraries (logging, system...)

265. Let’s see a gen_server in action!

266. Introducing Simple Key Value Store

267. A server that is able to store {Key, Value} and retrieve them by Key

268. Demo II

269. skvs diagram S P gs ets

270. skvs diagram S P gs ets

271. Starting skvs Go to skvs source directory Compile ./rebar compile Start the Erlang node erl -pa ebin Start the app application:start(skvs).

272. Some commands Set a value skvs_server:set(“Key”,”Value”). skvs_server:set(“Key2”,”Value2”). Get a value skvs_server:get(“Key2”).

273. Code on client: skvs_server.erl start_link() - gen_server:start_link({local, skvs}, skvs_server, [], []). get(Key) - gen_server:call(skvs, {get, Key}). set(Key,Value) - gen_server:call(skvs, {set, Key, Value}). set_fire_and_forget(Key,Value) - gen_server:cast(skvs, {set, Key, Value}).

274. Code on client: skvs_server.erl start

275. gen_server start_link() - gen_server:start_link({local, skvs}, skvs_server, [], []). get(Key) - gen_server:call(skvs, {get, Key}). set(Key,Value) - gen_server:call(skvs, {set, Key, Value}). set_fire_and_forget(Key,Value) - gen_server:cast(skvs, {set, Key, Value}).

277. gen_server start_link() - gen_server:start_link({local, skvs}, skvs_server, [], []). get(Key) - gen_server:call(skvs, {get, Key}). sync

278. call

279. to

280. server set(Key,Value) - (waits

281. for

282. reply) gen_server:call(skvs, {set, Key, Value}). set_fire_and_forget(Key,Value) - gen_server:cast(skvs, {set, Key, Value}).

284. gen_server start_link() - gen_server:start_link({local, skvs}, skvs_server, [], []). get(Key) - gen_server:call(skvs, {get, Key}). sync

285. call

286. to

287. server set(Key,Value) - (waits

288. for

289. reply) gen_server:call(skvs, {set, Key, Value}). set_fire_and_forget(Key,Value) - gen_server:cast(skvs, {set, Key, Value}). async

290. call

291. to

292. server (fire

294. forget)

295. Callback code: skvs_server.erl %% Client Callbacks on server %% Sync calls, expects response handle_call({set, Key, Value}, _From,State) - {reply, set_value(Key,Value), State}; handle_call({get, Key}, _From, State) - {reply, get_value(Key), State}. %% Async calls, do not expect response handle_cast({set, Key, Value}, State) - set_value(Key,Value), {noreply, State}.

296. Callback code: skvs_server.erl %% Client Callbacks on server %% Sync calls, expects response handle_call({set, Key, Value}, _From,State) - {reply, set_value(Key,Value), State}; handle_call({get, Key}, _From, State) - {reply, get_value(Key), State}. %% Async calls, do not expect response handle_cast({set, Key, Value}, State) - set_value(Key,Value), {noreply, State}. return

297. value

298. Callback code: skvs_server.erl %% Client Callbacks on server %% Sync calls, expects response handle_call({set, Key, Value}, _From,State) - {reply, set_value(Key,Value), State}; handle_call({get, Key}, _From, State) - {reply, get_value(Key), State}. %% Async calls, do not expect response handle_cast({set, Key, Value}, State) - set_value(Key,Value), {noreply, State}. Survives

299. between

300. return

301. value requests

302. Actual work...: skvs_server.erl %% Private functions set_value(Key, Value) - % Insert Key, Value into ETS. % Fail early {ok,Result}=case ets:insert(data_store,{Key,Value}) of true - {ok, {Key,Value}}; {error, Reason} - {error, Reason} end, Result.

303. Actual work...: skvs_server.erl %% Private functions set_value(Key, Value) - % Insert Key, Value into ETS. % Fail early {ok,Result}=case ets:insert(data_store,{Key,Value}) of true - {ok, {Key,Value}}; {error, Reason} - {error, Reason} end, ETS

304. is

305. a

306. Key

307. value

308. store

309. Result. in

310. RAM

311. Use cases

312. Gaming Industry

313. Gaming Industry

314. Messaging / IM

315. Messaging / IM

316. Payments

317. Payments

318. Databases

319. Databases

320. Others

321. Others

322. Some day...

323. Every highly interactive website? ;)

324. Pay Hello Ouch! Every highly interactive website? ;) Would you... Hey NO! ! Hi Buf

325. Internet of things

326. And now what?

327. Install Erlang/OTP! https://www.erlang-solutions.com/downloads/download-erlang-otp

328. Use a great IDE • IntelliJ + Erlang (plugin) • Sublime Text + SublimErl • Emacs

329. Read some books

330. RTFM • http://www.erlang.org/doc.html • http://erldocs.com/

331. Join mailing lists • Ofﬁcial Erlang mailing list • http://erlang.org/mailman/listinfo/erlang- questions • Join Barcelona Erlang user group on google groups

332. Find know-how • Check http://www.erlang-factory.com/ videos • Search for Erlang conferences on slideshare • Pray for an http://erlangcamp.com/ near your city

333. Read some code

334. This is the result of 6 months of fun learning Erlang/OTP

335. We are looking for awesome projects http://es.linkedin.com/in/jvalduvieco http://es.linkedin.com/in/jllonch

336. Thank you! https://github.com/jvalduvieco/betabeers_201303

337. Thank you! https://github.com/jvalduvieco/betabeers_201303 we

338. hope

339. you

340. feel

341. like

342. him

343. :) (we

344. did)

345. Erlang, The Movie http://www.youtube.com/watch?v=uKfKtXYLG78

346. Images sources http://diromero.wordpress.com/2011/10/07/home-automation/ http://iffergan.com/ http://technode.com/2012/05/14/internet-of-things-not-just-a-concept-for-fund-raising/ http://modernherstory.wordpress.com/2011/05/18/open-minds-open-hearts/ http://www.i-m.co/eviemouse/problemsolved/ http://strategicsalesmarketingosmg.wordpress.com/2012/06/25/who-are-twitter-users/ http://www.secureworks.com/it_security_services/advantage/soc/ http://labourlist.org/2011/11/my-biggest-worry-about-labour%E2%80%99s-future/broken-chain/ http://prothemedesign.com/how-to/why-you-should-keep-wordpress-and-your-plugins-up-to-date/attachment/matrix-code- update/ http://thegapbetweentwoworlds.com/category/career-transition http://www.wingweb.co.uk/Images/697/KC-10_Extender_SR-71_Blackbird http://www.tonywoodtraining.com/2010/11/29/motivation-to-exercise-and-eat-right/ http://portalmie.com/blog/6/2011/09/kushimoto-diving-park-tokushima-revista-no-7/ http://www.bcsagroup.com/ http://www.losemyaccent.com/tag/hand/ http://articulo.mercadolibre.com.ar/MLA-450970296-cortaplumas-victorinox-huntsman-15-usos-navaja-origen-suizo-_JM http://openclipart.org/detail/4112/ http://blog-en.coaching-go.com/2012/02/learn-to-say-no-and-know-how-to-say-yes/ok-2/ http://en.wikipedia.org/wiki/File:We_Can_Do_It!.jpg http://triniblog.wordpress.com/tag/laberintos/ http://www.catskillsnyrealestate.com/Want-More-Info-Catskill-Real-Estate.php http://www.thelovelyplanet.net/lush-green-images-planet-earth/ http://www.growthmax.com/how-exactly-does-growthmax-plus-make-you-grow-taller/ http://www.ayurvedalive.in/keep-your-eyes-healthy-beautiful http://my.mmosite.com/510619/blog/item/lord_of_the_rings_online.html http://sciﬁstorm.org/2010/03/24/lord-of-the-rings-blu-ray-review/ http://www.123rf.com/photo_15612022_3d-cartoon-bug.html http://www.airliners.net/photo/1134244/L/ http://www.muypymes.com/2009/12/04/moleskine-mucho-mas-que-una-agenda-personal http://learnyousomeerlang.com/the-hitchhikers-guide-to-concurrency http://planetpooks.com/one-more-reason-to-love-hermiones-handbag/

1 hour dive into Erlang/OTP

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