Erlang for Rubyists

given at the vienna.rb october 2013 meetup

1. (and Elixir) for Rubyists
2. Erlang is a programming language used to build massively scalable soft real-time systems with requirements on high availability.
9. BEAM OTP Process Node Message spawn
10. Operating System Operating System BEAM stdlib OTP Rails MRI ERTS STDLIB kernel Erlang Elixir JavaScript CoffeeScript Ruby Erlang/OTP
11. OS Process Erlang VM Erlang Node NOT Erlang Process Erlang Process Actor light-weight Thread NOT OS Process
12. Heap Mailbox Stack
13. **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" **********" One$.NET$4.0$Thread$$ (allocates$one$megabyte)$ One$Erlang$Process$(allocates$one$kilobyte)$ *$ @bryan_hunter
14. Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack
15. Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Message Heap Mailbox Stack
16. Heap Mailbox Stack Message
17. Mailbox Message 1 Message 2 Message 3 calculate something send message to P1 send message to P2 wait for incoming message calculate something send message to P1 wait for incoming message
18. wait for incoming message handle message by sending more messages and then waiting for answers from other processes send an answer message back
19. Who sends/receives messages? •other processes (obviously) •open files •open sockets •external programs (Ports) •Erlang VM notifications •a process you watched died •a remote node you watched died
20. Who sends/receives messages? •open files •“write this” •“read 15 bytes” -> “here are 15 bytes” •open sockets •“write this” •“some bytes just arrived” •external programs (Ports) •STDOUT/STDIN/STDERR
22. require  'actor' pong  =  nil ping  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000        pong  <<  (count  +  1)    end end pong  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000                ping  <<  (count  +  1)    end end ping  <<  1 sleep  1
23. defmodule  PingPong  do    def  start  do        :ok  =  :proc_lib.start_link(__MODULE__,  :init,  [:ping,  :pong])        :ok  =  :proc_lib.start_link(__MODULE__,  :init,  [:pong,  :ping])        :ping  <-­‐  1    end      def  init(my_name,  other_name)  do        Process.register(self(),  my_name)        :proc_lib.init_ack(:ok)        loop(my_name,  other_name)    end      def  loop(my_name,  other_name)  do        receive  do            count  -­‐>                other_name  <-­‐  (count  +  1)                if  count  >  1000  do                    IO.puts("#{my_name}  #{count}")                else                    loop(my_name,  other_name)                end        end    end end
24. -­‐module(pingpong). -­‐export([start/0,  init/2]).   start()  -­‐>    ok  =  proc_lib:start_link(?MODULE,  init,  [ping,  pong]),    ok  =  proc_lib:start_link(?MODULE,  init,  [pong,  ping]),    ping  !  1.   init(MyName,  OtherName)  -­‐>    true  =  erlang:register(MyName,  self()),    proc_lib:init_ack(ok),    loop(MyName,  OtherName).   loop(MyName,  OtherName)  -­‐>    receive        Count  -­‐>            OtherName  !  (Count  +  1),            case  Count  >  1000  of                true  -­‐>                    io:fwrite("~p  ~p~n",  [MyName,  Count]);                false  -­‐>                    loop(MyName,  OtherName)            end    end.
25. require  'actor' pong  =  nil ping  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000        pong  <<  (count  +  1)    end end pong  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000                ping  <<  (count  +  1)    end end ping  <<  1 sleep  1
26. require  'actor' pong  =  nil ping  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000        pong  <<  (count  +  1)    end end pong  =  Actor.spawn  do    loop  do        count  =  Actor.receive        break  puts(count)  if  count  >  1000        BCrypt::Password.create('secret',  cost:  50)  #  <-­‐-­‐  oh  well        ping  <<  (count  +  1)    end end ping  <<  1 sleep  1
27. calculate(something) calculate(something) calculate(something) calculate(something) calculate(something) calculate(something) calculate(something)
28. 2000 reductions left: calculate(something) 1000 reductions left: still calculating(something) 0 reductions left: suspend process run next process
29. 2000 reductions left: calculate(something) 1000 reductions left: still calculating(something) 0 reductions left: suspend process run next process green threads = cheap context switching
30. Supervisors
32. OTP Behaviours gen_server gen_fsm gen_event
35. Conn 1 Conn 2 Conn 3 Conn 4 Conn 5 Player 1 Player 2 Player 3 Player 4 Player 5 Table 1 Table 2 Game 1 Game 5
36. BERT Ernie bert-rpc.org
37. AT'SCALE'WITH'STYLE Erlang'<3'<3'<3'Ruby Mar$n&Rehfeld,&@klickmich
38. Distributed Erlang
39. Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack Heap Mailbox Stack
41. speakerrate.com/talks/26471 @MSch martin@apoch.io APOCH meetup.com/Vienna-BEAMers