A 5 minute introduction to Erlang

1. Erlang in a (real) nutshell
Lu´ Ferreira
ıs
Universidade do Minho
Semana da Lei II
zamith.28@gmail.com
July 13, 2010

2. What is Erlang?
Distributed
Lu´ Ferreira
ıs Erlang in a (real) nutshell

3. What is Erlang?
Distributed
Concurrent
Lu´ Ferreira
ıs Erlang in a (real) nutshell

4. What is Erlang?
Distributed
Concurrent
Fault-tolerant
Lu´ Ferreira
ıs Erlang in a (real) nutshell

5. What is Erlang?
Distributed
Concurrent
Fault-tolerant
Functional based
Lu´ Ferreira
ıs Erlang in a (real) nutshell

6. Why use Erlang?
NO
Number-crunching applications
Graphics intesive systems
Lu´ Ferreira
ıs Erlang in a (real) nutshell

7. Why use Erlang?
NO
Number-crunching applications
Graphics intesive systems
YES
High-level, concurrent, robust, soft real-time system that will
scale
Make full use of multicore processors
Integrate with components written in other languages
Lu´ Ferreira
ıs Erlang in a (real) nutshell

8. Some of the essential characteristics
Low memory overhead per process/task
Lu´ Ferreira
ıs Erlang in a (real) nutshell

9. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
Lu´ Ferreira
ıs Erlang in a (real) nutshell

10. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Lu´ Ferreira
ıs Erlang in a (real) nutshell

11. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Lu´ Ferreira
ıs Erlang in a (real) nutshell

12. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Functional/single-assignment
Lu´ Ferreira
ıs Erlang in a (real) nutshell

13. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Functional/single-assignment
Asynchronous message passing (send and pray) - Any Erlang
value
Lu´ Ferreira
ıs Erlang in a (real) nutshell

14. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Functional/single-assignment
Asynchronous message passing (send and pray) - Any Erlang
value
OS independent
Lu´ Ferreira
ıs Erlang in a (real) nutshell

15. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Functional/single-assignment
Asynchronous message passing (send and pray) - Any Erlang
value
OS independent
Messages retrieved selectively from the mailbox
Lu´ Ferreira
ıs Erlang in a (real) nutshell

16. Some of the essential characteristics
Low memory overhead per process/task
Thousands of processes - Own memory space, heap and stack
No ”global” errors. Stop errors propagating
Predictable performance
Functional/single-assignment
Asynchronous message passing (send and pray) - Any Erlang
value
OS independent
Messages retrieved selectively from the mailbox
Message passing by copy of data
Lu´ Ferreira
ıs Erlang in a (real) nutshell

17. Sequential Erlang
Sort
sort([Pivot|T]) ->
sort([X||X <- T, X =< Pivot]) ++
[Pivot] ++ sort([X||X <- T, X >= Pivot]);
sort([]) -> [].
Lu´ Ferreira
ıs Erlang in a (real) nutshell

18. Concurrent Erlang
Area Server
-module(server).
-export([start/0]).
start() ->
register(server,spawn(fun() -> loop(0) end)).
loop(Tot) ->
receive
{Pid, {square, X}} ->
Pid ! X*X,
loop(Tot + X*X);
{Pid, {rectangle,[X,Y]}} ->
Pid ! X*Y,
loop(Tot + X*Y);
{Pid, areas} ->
Pid ! Tot,
loop(Tot)
end.
Lu´ Ferreira
ıs Erlang in a (real) nutshell

19. Concurrent Erlang
Area Client
-module(client).
-export([square/1]).
square(Val) ->
server ! {self(),{square,Val}},
receive
Area ->
io:format("Area: ~p~n",[Val])
end.
Lu´ Ferreira
ıs Erlang in a (real) nutshell

20. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes Exception handle
Hot code replacement try return(X) when
Generic behaviours is integer(X) ->
... try return error(X) of
Val -> {normal,Val}
catch
exit:Reason ->
{exit,Reason}
throw:Throw ->
{throw,Throw}
error:Error ->
{error,Error}
end.
Lu´ Ferreira
ıs Erlang in a (real) nutshell

21. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes Trap exits
Hot code replacement process flag(trap exits,
Generic behaviours true),
... P = spawn link(Node, Mod,
Func, Args),
receive
{’EXIT’, P, Why}->
Actions;
...
end
Lu´ Ferreira
ıs Erlang in a (real) nutshell

22. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes
Hot code replacement
Generic behaviours
...
worker
supervisor
Lu´ Ferreira
ıs Erlang in a (real) nutshell

23. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes
Hot code replacement
Generic behaviours
...
Lu´ Ferreira
ıs Erlang in a (real) nutshell

24. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes
Hot code replacement
Generic behaviours
...
Lu´ Ferreira
ıs Erlang in a (real) nutshell

25. Other features
Fault tolerance (catch/throw)
Trapping exits
Linked processes
Hot code replacement
Generic behaviours
...
Lu´ Ferreira
ıs Erlang in a (real) nutshell