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-module(erlbal_n).
-export([make_request/2, start_bal/0, stop_bal/1, start_server/5, stop_server/2, list_servers/1]).
start_server(Balancer, Node, Fun, LoadFun, INITSTATE) when is_function(Fun, 2) andalso is_function(LoadFun, 0) andalso is_list(INITSTATE) ->
PID = spawn(Node, fun() -> server_loop(Fun, LoadFun, INITSTATE) end),
Balancer ! {add_node, PID}.
stop_server(Balancer, PID) ->
Balancer ! {del_node, PID},
PID ! die.
list_servers(Balancer) ->
Balancer ! {list_nodes, self()},
receive Nodes -> Nodes end.
server_loop(Fun, LoadFun, STATE) ->
receive
{request, From, Serverlist, ARGS} ->
{Ret, NEWSTATE} = Fun(ARGS, STATE),
From ! Ret,
updatestates(Serverlist, self(), NEWSTATE),
server_loop(Fun, LoadFun, NEWSTATE);
{load, From} ->
From ! LoadFun(),
server_loop(Fun, LoadFun, STATE);
{update, NEWSTATE} ->
server_loop(Fun, LoadFun, NEWSTATE);
die ->
ok
end.
updatestates([], _, _) ->
ok;
updatestates([H|T], H, NEWSTATE) ->
updatestates(T, H, NEWSTATE);
updatestates([H|T], P, NEWSTATE) ->
H ! {update, NEWSTATE},
updatestates(T, P, NEWSTATE).
start_bal() ->
spawn(fun() -> bal_loop([]) end).
stop_bal(Balancer) ->
Balancer ! die.
bal_loop(Serverlist) ->
receive
{add_node, PID} ->
bal_loop(Serverlist ++ [PID]);
{del_node, PID} ->
bal_loop(Serverlist -- [PID]);
{list_nodes, From} ->
From ! Serverlist,
bal_loop(Serverlist);
{request, From, ARGS} ->
if
length(Serverlist) > 0 ->
PID = bal_worker(Serverlist),
PID ! {request, From, Serverlist, ARGS},
bal_loop(Serverlist);
true ->
bal_loop(Serverlist)
end;
die ->
ok
end.
bal_worker([H|T]) ->
H ! {load, self()},
receive
N ->
bal_worker(T, N, H)
end.
bal_worker([], _, PID) ->
PID;
bal_worker([H|T], Best, PID) ->
H ! {load, self()},
receive
N ->
if
N > Best ->
bal_worker(T, N, H);
true ->
bal_worker(T, Best, PID)
end
end.
make_request(Balancer, ARGS) when is_list(ARGS)->
Balancer ! {request, self(), ARGS},
receive Ret -> Ret end.
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