Slides from my talk at the Vancouver Erlang Meetup Group on November 9th 2009. See: http://www.meetup.com/erlang-vancouver/events/11730648/

1. Introduction to Distributed
Erlang
Basic principles and a little more

2. About us
Developing a new breed of platform for social
networking games
Scalability is a must
Back-end developed with Erlang/OTP
And lots of other good stuff
Front-end developed with Flex 4

3. About me
More stickers than a 40 years old RV!

4. Agenda and non-agenda
Quick recap of message passing
Core principles of Erlang remoting
Global registry and process groups
Nothing on Erlang syntax {<<"sorry">>}
Nothing on custom networking nor OTP
OTP is what you'll use in reality

5. Why Erlang for concurrency?
Immutability painted all over it
Designed to handle thousands of processes
Spawned (not started nor forked)
Processes communicate asynchronously
Passing messages by value

6. Message sending
As easy as:
Pid ! Message
Sends a message to a process inbox
Like with mail delivery:
Not sure if the letter reached its destination
Needs a letter back if a response is needed

7. RSVP
Add address on the envelope for a response

8. RSVP (client)
Client is also
Server's public
API
send(Sid, Message) ->
Sid!{self(), Message},
receive
{From, Response} ->
io:format("Client ~p from ~p~n",
[Response, From])
after
1000 -> bail
end.

9. RSVP (server)
start() ->
spawn(fun()-> serve() end).
serve() ->
receive
{From, Message} ->
io:format("Server ~p from ~p~n",
[Message, From]),
From!{self(), {ack, Message}},
serve()
end.

10. Process registration
Allows process naming:
register(my_pid, Pid).
Frees application from passing Pids around:
my_pid ! Message.

11. RPC strikes back
Call MFA on single or multiple nodes
Declined in zillions of variations:
Blocking or not
Parallelized, including pmap
Makes code location aware
Heterogeneous styles:
Pid ! Message
rpc:call(N,M,F,A)

12. Node connectivity
Triggered by:
rpc:call ...
net_adm:ping(node@host)
Nodes shake hands and share information
Processes, registrations...
Transitive mechanism
Node 1 ➟ Node 2 and Node 2 ➟ Node3
then: Node 1 ➟ Node 3

13. Erlang Port Mapper Daemon

14. Erlang's magic cookie
Passed on startup:
erl -sname n1 -setcookie=secret
Proper node and host naming required
Coarse grained security
Party time or bust!

15. Global process registry
Location transparency:
global:register_name(gbs, Sid).
global:whereis_name(gbs) ! Message.
Wired-in name conflict resolution
Still need to ping nodes

16. Process group (1/3)
Distributed named process group
Processes join and leave:
pg2:create(mypg2).
pg2:join(mypg2, Sid).
pg2:leave(mypg2, Sid).

17. Process group (2/3)
pg2 can be used to send messages to:
all processes:
pg2:get_members(mypg2)
local processes:
pg2:get_local_members(mypg2)
closest / random process:
pg2:get_closest_pid(mypg2)

18. Process group (3/3)
Also: pg (experimental)

19. Ping pong pang relief
net_adm:world and net_adm:world_list
Ease node discovery on hosts
Requires hosts list
Node discovery with nodefinder
UDP multicast
S3 list for AWS

20. Probing further

21. Thank you!