Introduction To Distributed Erlang
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The document provides an introduction to distributed Erlang and its core principles, focusing on the development of a social networking games platform using Erlang/OTP for back-end scalability. Key topics include message passing, process communication, and global process registry, along with practical examples of client-server interactions and process group management. It emphasizes the ease of using Erlang for concurrency, the need for immutability, and the mechanisms for node connectivity and discovery.
![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.](https://image.slidesharecdn.com/introductiontodistributederlang-100107101322-phpapp01/85/Introduction-To-Distributed-Erlang-8-320.jpg)
![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.](https://image.slidesharecdn.com/introductiontodistributederlang-100107101322-phpapp01/85/Introduction-To-Distributed-Erlang-9-320.jpg)
Introduction To Distributed Erlang
- 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!