The Basic Loop
-module(translate).
-export([loop/0]).
loop() ->
receive
"casa" ->
io:format("house~n"),
loop();
"blanca" ->
io:format("white~n"),
loop();
_ ->
io:format("I don't understand.~n"),
loop()
end.
Spawning a Process
Pid = spawn(fun translate:loop/0).
Sending Messages
Pid ! "casa".
Pid ! "blanca".
Pid ! "loco".
Receiving Messages
translate_service.erl
Translator = spawn(fun translate_service:loop/0)
translate_service:translate(Translator, "blanca").
translate_service:translate(Translator, "casa")
3 Idioms for Concurrency
I don't care
spawn(Fun) -> pid()
spawn(Node, Fun) -> pid()
spawn(Module, Function, Args) -> pid()
spawn(Node, Module, Function, Args) -> pid()
Let it crash
spawn_link(Fun) -> pid()
spawn_link(Node, Fun) -> pid()
spawn_link(Module, Function, Args) -> pid()
spawn_link(Node, Module, Function, Args) -> pid()
Let me know
process_flag(trap_exit, true),
spawn_link(...)
process_flag(trap_exit, true),
link(...)
Linked Processes
When a linked process dies, it sends a termination signal to its linkees
-module(roulette).
-export([loop/0]).
loop() ->
receive
3 -> io:format("bang.~n"),
exit({roulette,die,at,erlang:time()});
_ -> io:format("click~n"), loop()
end.
Linked Processes
c(roulette).
Gun = spawn(fun roulette:loop/0).
erlang:is_process_alive(Gun).
Linked Processes - Monitor
Let's you know if a process dies
-module(coroner).
-export([loop/0]).
loop() ->
process_flag(trap_exit, true),
receive
{monitor, Process} ->
link(Process),
io:format("Monitoring process.~n"),
loop();
{'EXIT', From, Reason} ->
io:format("The shooter ~p died with reason ~p.",
[From, Reason]),
io:format("Start another one.~n"),
loop()
end.
Linked Processes - Monitor
Let's you know if a process dies
-module(coroner).
Revolver=spawn(fun roulette:loop/0).
Coroner=spawn(fun coroner:loop/0).
Coroner ! {monitor, Revolver}.
Linked Processes - Monitor
Can also re-spawn a process
-module(doctor).
-export([loop/0]).
loop() ->
process_flag(trap_exit, true),
receive
new ->
io:format("Creating and monitoring process.~n"),
register(revolver, spawn_link(fun roulette:loop/0)),
loop();
{'EXIT', From, Reason} ->
io:format("The shooter ~p died with reason ~p.",
[From, Reason]),
io:format(" Restarting. ~n"),
self() ! new,
loop()
end.
Assignment
Keep working on the Assignment
