A Chat About Erlang

Transcript

1. A Chat About Erlang Bryce Kerley Miami Ruby Brigade February 18, 2013 Monday, February 18, 13
2. Administrativia Please check on on the Meetup iPhone or Android app. Monday, February 18, 13
3. Who Am I? Consulting Engineer Basho Technologies bryce@basho.com @bonzoesc Monday, February 18, 13
4. Disclaimer The thoughts, views, and opinions in this presentation are mine, and not my employer’s. Monday, February 18, 13
5. Hello World io:format("Hello World\n"). Monday, February 18, 13
6. What is Erlang? Functional Distributed Reliable Monday, February 18, 13
7. 1> X = 5. 5 2> Y = X. 5 3> 5 = Y. 5 4> Y = 6. ** exception error: no match Erlang is Functional Monday, February 18, 13
8. 5 3> 5 = Y. 5 4> Y = 6. ** exception error: no match 5> Z = fun(N) -> N * 2 end. #Fun<erl_eval.6.80247286> 6> Z. #Fun<erl_eval.6.80247286> 7> Z(5). 10 Erlang is Functional Monday, February 18, 13
9. Erlang is Distributed > ./bin/riak attach Attaching to riak_ee-1.2.1rc2/dev/dev1 (^D to exit) (dev1@127.0.0.1)1> nodes(). ['dev2@127.0.0.1','dev3@127.0.0.1','dev4@127.0.0.1', 'dev5@127.0.0.1','dev6@127.0.0.1'] Monday, February 18, 13
10. Erlang is Reliable Illustration by Fred Hébert, from “Learn You Some Erlang for Great Good!” Monday, February 18, 13
11. Monday, February 18, 13
12. What is Erlang? Functional Distributed Reliable Monday, February 18, 13
13. What is Ruby? Object-Oriented Functional Rich Syntax Flexible Monday, February 18, 13
14. What is Ruby bad at? Multitasking Garbage collection Predictability Monday, February 18, 13
15. What is Erlang good at? Multitasking Garbage collection Predictability Monday, February 18, 13
16. Hello World io:format("Hello World\n"). Monday, February 18, 13
17. Hello World io:format("Hello World\n"). module Monday, February 18, 13
18. Hello World io:format("Hello World\n"). module function Monday, February 18, 13
19. Hello World io:format("Hello World\n"). module function string Monday, February 18, 13
20. Hello World io:format("Hello World\n"). module function string newline Monday, February 18, 13
21. Hello World io:format("Hello World\n"). module function string newline end statement Monday, February 18, 13
22. Syntax handle_event(_Event,  _StateName,  StateData)  -­‐>        {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 Monday, February 18, 13
23. Syntax handle_event(_Event,  _StateName,  StateData)  -­‐>        {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function Monday, February 18, 13
24. Syntax handle_event(_Event,  _StateName,  StateData)  -­‐>        {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function arguments Monday, February 18, 13
25. Syntax handle_event(_Event,  _StateName,  StateData)  -­‐>        {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function arguments symbol Monday, February 18, 13
26. Syntax handle_event(_Event,  _StateName,  StateData)  -­‐>        {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function arguments symbol tuple Monday, February 18, 13
27. Pattern Matching More useful than equality More powerful than method overloading describe_error(Desc,  [],  [trashed])  -­‐>   {obserror,  Desc}; describe_error(Desc,  [],  Stack)  -­‐>   {obserror,  format("~s.  Stack  ~w",  [Desc,  Stack])}; describe_error(Desc,  Rest,  Stack)  -­‐>   {obserror,  format("~s.    Rest:  ~w  Stack  ~w",  [Desc,  Rest,  Stack])}. Monday, February 18, 13
28. Data Types •List •Tuple •Integer •Float •Atom (symbol) •Bit String Monday, February 18, 13
29. Data Types •Fun: anonymous function, closure •Reference: unique ID •Port identifier: pointer to an I/O port •Pid: pointer to an Erlang process Monday, February 18, 13
30. Synthetic Data Types •Binary: a Bit String with a multiple of 8 bits •String: a List of Integers •Record: a Tuple enforced by the compiler •IO List: a List of Integers, Binaries, and IO Lists; or a Binary •Boolean: the atoms true and false Monday, February 18, 13
31. Environment •Process: similar to a thread •Module: collection of functions •Macro: preprocessor facility (like C) Monday, February 18, 13
32. Process Monday, February 18, 13
33. Process •No shared memory Monday, February 18, 13
34. Process •No shared memory •Asynchronous messaging Monday, February 18, 13
35. Process •No shared memory •Asynchronous messaging •Garbage collected independently Monday, February 18, 13
36. Process •No shared memory •Asynchronous messaging •Garbage collected independently •Fast to create, fast to destroy Monday, February 18, 13
37. Process •No shared memory •Asynchronous messaging •Garbage collected independently •Fast to create, fast to destroy •Low overhead Monday, February 18, 13
38. Open Telecom Platform Illustration by Fred Hébert, from “Learn You Some Erlang for Great Good!” Monday, February 18, 13
39. Behaviors Similar to Ruby mixins Think Enumerable You implement callbacks Behavior supplies the rest Monday, February 18, 13
40. gen_server Generic server Has state Takes synchronous calls, returns responses Takes asynchronous casts Monday, February 18, 13
41. gen_server You Write It Does init turns arguments into state handle_call synchronous, respond and new state handle_cast asynchronous, new state handle_info timeout, new state terminate clean up code_change just upgraded, new state Monday, February 18, 13
42. gen_server State: whatever you want Last argument Last element in response tuple handle_call(all_vnodes_status,  _From,  State)  -­‐>        Reply  =  get_all_vnodes_status(State),        {reply,  Reply,  State}; https://github.com/basho/riak_core/blob/1276e4e926b7007262f7631a27cdb4ecf6cbcaaf/src/riak_core_vnode_manager.erl#L260-L262 Monday, February 18, 13
43. Other Behaviors gen_fsm: finite state machine gen_event: event dispatch and handling supervisor: keep trees of servers, fsms, events, etc. alive Monday, February 18, 13
44. rebar Think Rake Generate scaffolds Run build tasks Monday, February 18, 13
45. Riak Open-source database Built with Erlang, OTP, rebar, webmachine Great for sanity checking implementation Monday, February 18, 13
46. riak_core Distributed system framework powering Riak Nice starting point Monday, February 18, 13
47. What is Erlang bad at? Prolog syntax Opinionated rules No Rails-tier web frameworks Monday, February 18, 13
48. What is Ruby good at? Friendly syntax Few rules, lots of customizability Great frameworks Monday, February 18, 13
49. Should I Use Erlang? Monday, February 18, 13
50. Should I Use Erlang? Yes* Monday, February 18, 13
51. Should I Use Erlang? Yes* *If it makes sense Monday, February 18, 13
52. Use Cases Social network Real-time chat Code sharing site Monday, February 18, 13
53. Learn You Some Erlang http://learnyousomeerlang.com http://nostarch.com/erlang Monday, February 18, 13
54. Links http://bit.ly/erlang-miamirb http://erlang.org/ http://learnyousomeerlang.com/ https://github.com/basho/rebar/ https://github.com/basho/rebar_riak_core/ Monday, February 18, 13