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129 rivejä
4.1 KiB
129 rivejä
4.1 KiB
-module(gen_call).
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-export([gcall/3, gcall/4, greply/2]).
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-define(default_timeout, 5000).
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%% We trust the arguments to be correct, i.e
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%% Process is either a local or remote pid,
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%% or a {Name, Node} tuple (of atoms) and in this
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%% case this node (node()) _is_ distributed and Node =/= node().
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-define(get_node(Process), case Process of {_S, N} -> N; _ -> node(Process) end).
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gcall(Process, Label, Request) ->
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gcall(Process, Label, Request, ?default_timeout).
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gcall(Process, Label, Request, Timeout) ->
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%%-----------------------------------------------------------------
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%% Map different specifications of a process to either Pid or
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%% {Name,Node}. Execute the given Fun with the process as only
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%% argument.
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%% -----------------------------------------------------------------
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case where(Process) of
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undefined ->
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exit(noproc);
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PidOrNameNode ->
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%Node = ?get_node(PidOrNameNode),
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try do_call(PidOrNameNode, Label, Request, Timeout)
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catch
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exit:{nodedown, _Node} ->
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%% A nodedown not yet detected by global, pretend that it was.
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exit(noproc)
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end
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end.
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-dialyzer({no_improper_lists, do_call/4}).
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do_call(Process, Label, Request, Timeout) ->
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CurNode = node(),
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case ?get_node(Process) of
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CurNode ->
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Mref = erlang:monitor(process, Process),
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%% Local without timeout; no need to use alias since we unconditionally
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%% will wait for either a reply or a down message which corresponds to
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%% the process being terminated (as opposed to 'noconnection')...
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case self() of
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Process ->
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exit(calling_self);
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_ ->
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Process ! {Label, {self(), Mref}, Request},
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end,
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receive
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{Mref, Reply} ->
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erlang:demonitor(Mref, [flush]),
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{ok, Reply};
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{'DOWN', Mref, _, _, Reason} ->
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exit(Reason)
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after Timeout ->
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erlang:demonitor(Mref, [flush]),
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receive
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{[alias | Mref], Reply} ->
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{ok, Reply}
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after 0 ->
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exit(timeout)
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end
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end;
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_PNode ->
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Mref = erlang:monitor(process, Process, [{alias, demonitor}]),
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Tag = [alias | Mref],
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%% OTP-24:
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%% Using alias to prevent responses after 'noconnection' and timeouts.
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%% We however still may call nodes responding via process identifier, so
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%% we still use 'noconnect' on send in order to try to send on the
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%% monitored connection, and not trigger a new auto-connect.
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%%
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erlang:send(Process, {Label, {self(), Tag}, Request}, [noconnect]),
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receive
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{[alias | Mref], Reply} ->
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erlang:demonitor(Mref, [flush]),
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{ok, Reply};
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{'DOWN', Mref, _, _, noconnection} ->
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exit({nodedown, _PNode});
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{'DOWN', Mref, _, _, Reason} ->
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exit(Reason)
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after Timeout ->
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erlang:demonitor(Mref, [flush]),
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receive
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{[alias | Mref], Reply} ->
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{ok, Reply}
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after 0 ->
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exit(timeout)
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end
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end
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end.
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where({global, Name}) -> global:whereis_name(Name);
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where({local, Name}) -> whereis(Name);
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where({via, Module, Name}) -> Module:whereis_name(Name);
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where({Name, Node} = Process) ->
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CurNode = node(),
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case CurNode of
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Node ->
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whereis(Name);
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nonode@nohost ->
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exit({nodedown, Node});
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_ when is_atom(Name), is_atom(Node) ->
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Process;
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_ ->
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undefined
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end;
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where(Name) ->
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if
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is_pid(Name) ->
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Name;
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is_atom(Name) ->
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whereis(Name);
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true ->
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undefined
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end.
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%%
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%% Send a reply to the client.
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%%
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greply({_To, [alias | Alias] = Tag}, Reply) when is_reference(Alias) ->
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Alias ! {Tag, Reply}, ok;
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greply({_To, [[alias | Alias] | _] = Tag}, Reply) when is_reference(Alias) ->
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Alias ! {Tag, Reply}, ok;
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greply({To, Tag}, Reply) ->
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try To ! {Tag, Reply}, ok catch _:_ -> ok end.
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