A story of a Ruby programmer having to understand that learning Erlang is more than just syntax. Learn differences in paradigms, pitfalls and applied use cases for this incredibly powerful language

1. More than
Syntax

2. Patrick Huesler
@phuesler

3. More than
Syntax

4. web apis with
erlang
a ruby dev’s POV

5. snow
boarding

6. Surfing

7. WIPEOUT

8. erlang

9. I’m an erlang
beginner
so don’t believe everything
I say

10. this is not an
erlang
introduction

11. erlang
refresher

12. functional
language

13. runtime
system

14. open telecom platform
OTP

15. why
erlang?

17. seriously
concurrent

18. with built in
actors

19. because it is
distributed

20. fault
tolerant

22. hot
swaping

23. remote
shell

24. erlang at
wooga

28. technical
challenges

29. monthly active users
20,543,500
for Diamond Dash
http://www.appdata.com/apps/facebook/127995567256931-diamond-dash (03/10/2012)

30. daily active users
3,871,133
for Diamond Dash
http://www.appdata.com/apps/facebook/127995567256931-diamond-dash (03/10/2012)

31. backend traffic up to
6,500 RPS
for Monster World

32. what does mean that for a
Database?

33. read/write ratio?
write heavy

34. different
architectures

35. no
database
is faster than no database

36. stateful

37. Let’s use
S3
all the way

38. http://www.slideshare.net/wooga/from-0-to-1000000-daily-users-with-erlang

39. http://www.slideshare.net/wooga/from-0-to-1000000-daily-users-with-erlang

40. processes are
cheap
in erlang

41. erlang
Web APIs

42. rebar

43. $:rebar create-app appid=aloha

44. how to manage
dependencies
like rubygems does?

45. rebar

46. $: rebar get-deps
$: rebar compile
$: rebar get-deps compile

47. 1 % Compiler Options for rebar
2 {erl_opts, [
3 {src_dirs, ["src", "test"]},
4 debug_info
5 ]}.
6
7 % Dependencies
8 {deps, [
9 {elli, ".*", {git, "git://github.com/knutin/elli.git", "HEAD"}},
10 {etest, ".*", {git, "git://github.com/wooga/etest.git", "HEAD"}},
11 {etest_http, ".*", {git, "git://github.com/wooga/etest_http.git",
HEAD"}}
12 ]}.
13
14 % Which files to cleanup when rebar clean is executed.
15 {clean_files, ["ebin/*.beam"]}.

48. What
webserver
shall we use?

49. elli

50. 1 elli:start_link([
2 {callback, aloha_api},
3 {port, 3000}
4 ])

51. how do I do
Routing?

52. 1 Path = [<<"foo">>, <<"bar">>],
2 HTTPMethod = "GET",
3 Request = {HTTPMethod, Path},
4 RouteDefinitions = [{{"GET",[<<"foo">>,<<"bar">>]},
{my_handler, my_method, []}}],
5 case erl_route_url:match(Request, RouteDefinitions) of
6 {error, notfound} ->
7 io:format("path not found");
8 {ok, Params, {M,F,_}} ->
9 apply(M,F,Params)
10 end.

53. you’re doing it
wrong!!!

54. use
pattern
matching

55. 1 handle(Req, _Args) ->
2 Path = elli_request:path(Req),
3 handle(Req#req.method, Path, Req).
4
5 handle('GET',[<<"foo">>, <<"bar"], Req) ->
6 {ok, [], <<"kekahi mau pipi">>};
7
8 handle(_, _, _Req) ->
9 {404, [], <<"wipe out!">>}.

56. does it support
middleware?

57. 1 Config = [
2 {mods, [
3 {aloha_ware, []},
4 {mahalo_ware, []},
5 ]}
6 ],
7
8 elli:start_link([
9 {callback, aloha_api},
10 {port, 3000},
11 {callback_args, Config}
12 ]).

58. events
request_complete
request_throw
request_exit
request_error
request_parse_error
bad_request
client_closed
client_timeout
elli_startup

59. 1 handle_event(request_complete, [
2 Req,
3 ResponseCode,
4 ResponseHeaders,
5 ResponseBody,
6 Timings
7 ], Config) ->
8
9 TimingKeys = [
10 accepted,
11 request_start,
12 heades_end,
13 body_end,
14 user_start,
15 user_end,
16 request_end
17 ],
18 ok;

60. awesome
monitoring

61. 1 handle_event(request_throw, [
2 Req,
3 Exception,Stack
4 ], _Config) ->
5 ok;
6
7 handle_event(request_exit, [
8 Req,
9 Exit,
10 Stack
11 ], _Config) ->
12 ok;
13
14 handle_event(request_error, [
15 Req,
16 Error,
17 Stack
18 ], _Config) ->
19 ok;
20

62. how about
environments?

63. $: erl -pa deps/*/ebin ebin n
-config myconfig

64. 1 [
Config file
2 {aloha, [
3 {worker_port, 3333}
4 ]
5 },
6
7 {lager, [
8 {handlers, [
9 {lager_console_backend, debug},
10 {lager_file_backend, [
11 {"log/debug.log", debug, 10485760, "$D0", 5},
12 {"log/error.log", error, 10485760, "$D0", 5},
13 {"log/console.log", info, 10485760, "$D0", 5}
14 ]}
15 ]}
16 ]}
17 ].

65. how about
logging?

66. 1 error_logger:info_msg("alohan").
2 % prints alohanok
3
4 error_logger:warning_msg("freak set").
5 % prints freak set ahead nok
6
7 error_logger:error_msg("wipe outn").
8 % prints wipe outnok

67. sasl

68. =PROGRESS REPORT==== 8-Oct-2012::12:06:24 ===
supervisor: {local,sasl_safe_sup}
started: [{pid,<0.39.0>},
{name,overload},
{mfargs,{overload,start_link,
[]}},
{restart_type,permanent},
{shutdown,2000},
{child_type,worker}]
=PROGRESS REPORT==== 8-Oct-2012::12:06:24 ===
supervisor: {local,sasl_sup}
started: [{pid,<0.37.0>},
{name,sasl_safe_sup},
{mfargs,
{supervisor,start_link,
[{local,sasl_safe_sup},sasl,safe]}},

69. how about
unix style?

70. lager

71. 1 [
Config file
2 {aloha, [
3 {worker_port, 3333}
4 ]
5 },
6
7 {lager, [
8 {handlers, [
9 {lager_console_backend, debug},
10 {lager_file_backend, [
11 {"log/debug.log", debug, 10485760, "$D0", 5},
12 {"log/error.log", error, 10485760, "$D0", 5},
13 {"log/console.log", info, 10485760, "$D0", 5}
14 ]}
15 ]}
16 ]}
17 ].

72. 1 start(_StartType, _StartArgs) ->
2 ok = application:start(compiler),
3 ok = application:start(syntax_tools),
4 ok = application:start(lager),
5
6 % start mochiweb module reloader
7 reloader:start(),
8
9 elli:start_link([{callback, aloha_api}, {port, 3000}]),
10 aloha_sup:start_link().

73. 1 dev_start(App) -> dev_start(App, temporary).
2
3 dev_start(App, Type) ->
4 case application:start(App, Type) of
5 {error, {not_started, DepApp}} ->
6 dev_start(DepApp),
7 dev_start(App, Type);
8 ok -> ok;
9 {error, {already_started, App}} -> ok
10 end.

74. 1 lager:debug("alohan").
2 % prints alohanok
3
4 lager:warning("freak set").
5 % prints freak set ahead nok
6
7 lager:error("wipe outn").
8 % prints wipe outnok

75. how about
Unit
testing?

76. eunit

77. no
stacktrace
the easy way

78. etest

79. 1 -module(aloha_utils_test).
2 -compile(export_all).
3
4 % Include etest's assertion macros.
5 -include_lib("etest/include/etest.hrl").
6
7 before_suite() ->
8 %start up applications
9 ok.
10
11 before_test() ->
12 %load fixtures
13 ok.
14
15 test_hello() ->
16 ?assert_equal("kekahi mau pipi", aloha_utils:hello()).
17
18 after_test() ->
19 % tear down fixtures
20 ok.
21
22 after_suite() ->
23 % stop applications
24 ok.

80. $: ./deps/etest/bin/etest-runner

81. How about
http
testing?

82. 1 -module (aloha_api_test).
2 -compile (export_all).
3
4 % etest macros
5 -include_lib ("etest/include/etest.hrl").
6 % etest_http macros
7 -include_lib ("etest_http/include/etest_http.hrl").
8
9 before_suite() ->
10 application:start(aloha).
11
12 before_test() -> ok.
13
14 after_test() -> ok.
15
16 after_suite() ->
17 application:stop(aloha).
18
19 test_aloha() ->
20 Response = ?perform_get("http://localhost:3000/aloha"),
21 ?assert_status(200, Response),
22 ?assert_body("kekahi mau pipi", Response).

83. $: ./deps/etest/bin/etest-runner

84. how about
auto
reload?

85. Mochiweb
reloader

86. 1 start(_StartType, _StartArgs) ->
2 ok = application:start(compiler),
3 ok = application:start(syntax_tools),
4 ok = application:start(lager),
5
6 % start mochiweb module reloader
7 reloader:start(),
8
9 elli:start_link([{callback, aloha_api}, {port, 3000}]),
10 aloha_sup:start_link().

87. beware of
NIFs

89. how about
auto
compile?

90. guard

91. 1 # # -*- encoding : utf-8 -*-
2
3 guard 'shell' do
4 watch(%r{^src/.+.erl$}) do |m|
5 puts `rebar compile`
6 end
7 end

92. how ab bout
deploying to
heroku?

93. $: heroku create aloha-erl -s cedar

94. Heroku
buildpack

95. $: heroku config:add
BUILDPACK_URL=http://github.com/
heroku/heroku-buildpack-
erlang.git

96. procfile

97. web: erl -pa deps/*/ebin ebin
-noshell
-noinput
-config priv/config/
environments/development
-s aloha_app

98. 1 start(_StartType, _StartArgs) ->
2 ok = application:start(compiler),
3 ok = application:start(syntax_tools),
4 ok = application:start(lager),
5 reloader:start(),
6
7 {ok, DefaultPort} = application:get_env(aloha, worker_port),
8 Port = get_port(DefaultPort),
9
10 elli:start_link([{callback, aloha_api}, {port, Port}]),
11 aloha_sup:start_link().
12
13 get_port(Default) ->
14 Key = "PORT",
15 case os:getenv(Key) of
16 false -> Default;
17 Val -> list_to_integer(Val)
18 end.

99. foreman

100. $: foreman start

101. deploy

102. $: git push heroku master

103. -----> Heroku receiving push
-----> Fetching custom git buildpack... done
-----> Erlang app detected
-----> Installing Rebar from buildpack
-----> Building with Rebar
==> build_1us6u0b7p5agc (get-deps)
Pulling etest from {git,"git://github.com/wooga/etest.git","HEAD"}
......
Compiled src/aloha_api.erl
-----> Discovering process types
Procfile declares types -> web
-----> Compiled slug size: 6.3MB
-----> Launching... done, v19
http://aloha-erl.herokuapp.com deployed to Heroku
To git@heroku.com:aloha-erl.git
4bf3f39..198ba04 master -> master

104. $:curl aloha-erl.herokuapp.com/
aloha

105. aloha-erl.herokuapp.com

106. that’s it folks
mahalo

107. thanks to
• https://twitter.com/wooga
• https://twitter.com/knutin
• https://twitter.com/hukl
• https://twitter.com/hungryblank
• https://twitter.com/guillermoo
•https://twitter.com/klickmich
• Andreas hasselberg
• Johannes Huning

108. Resources
• https://github.com/phuesler/aloha_erl
• http://vimeo.com/45212367
• https://github.com/knutin/elli
• https://github.com/wooga/etest
• https://github.com/wooga/etest_http
• https://github.com/basho/lager
• https://github.com/mochi/mochiweb/blob/master/src/reloader.erl
• https://github.com/heroku/heroku-buildpack-erlang

109. media
• Erlang: The Movie - YouTube
• bomb: http://www.flickr.com/photos/7969902@N07/511234695/