%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2010. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
-module(gen).
%%%-----------------------------------------------------------------
%%% This module implements the really generic stuff of the generic
%%% standard behaviours (e.g. gen_server, gen_fsm).
%%%
%%% The standard behaviour should export init_it/6.
%%%-----------------------------------------------------------------
-export([start/5, start/6, debug_options/1,
call/3, call/4, reply/2]).
-export([init_it/6, init_it/7]).
-export([format_status_header/2]).
-define(default_timeout, 5000).
%%-----------------------------------------------------------------
-type linkage() :: 'link' | 'nolink'.
-type emgr_name() :: {'local', atom()} | {'global', term()}.
-type start_ret() :: {'ok', pid()} | 'ignore' | {'error', term()}.
-type debug_flag() :: 'trace' | 'log' | 'statistics' | 'debug'
| {'logfile', string()}.
-type option() :: {'timeout', timeout()}
| {'debug', [debug_flag()]}
| {'spawn_opt', [proc_lib:spawn_option()]}.
-type options() :: [option()].
%%-----------------------------------------------------------------
%% Starts a generic process.
%% start(GenMod, LinkP, Mod, Args, Options)
%% start(GenMod, LinkP, Name, Mod, Args, Options)
%% GenMod = atom(), callback module implementing the 'real' fsm
%% LinkP = link | nolink
%% Name = {local, atom()} | {global, term()}
%% Args = term(), init arguments (to Mod:init/1)
%% Options = [{timeout, Timeout} | {debug, [Flag]} | {spawn_opt, OptionList}]
%% Flag = trace | log | {logfile, File} | statistics | debug
%% (debug == log && statistics)
%% Returns: {ok, Pid} | ignore |{error, Reason} |
%% {error, {already_started, Pid}} |
%% The 'already_started' is returned only if Name is given
%%-----------------------------------------------------------------
-spec start(module(), linkage(), emgr_name(), module(), term(), options()) ->
start_ret().
start(GenMod, LinkP, Name, Mod, Args, Options) ->
case where(Name) of
undefined ->
do_spawn(GenMod, LinkP, Name, Mod, Args, Options);
Pid ->
{error, {already_started, Pid}}
end.
-spec start(module(), linkage(), module(), term(), options()) -> start_ret().
start(GenMod, LinkP, Mod, Args, Options) ->
do_spawn(GenMod, LinkP, Mod, Args, Options).
%%-----------------------------------------------------------------
%% Spawn the process (and link) maybe at another node.
%% If spawn without link, set parent to ourselves 'self'!!!
%%-----------------------------------------------------------------
do_spawn(GenMod, link, Mod, Args, Options) ->
Time = timeout(Options),
proc_lib:start_link(?MODULE, init_it,
[GenMod, self(), self(), Mod, Args, Options],
Time,
spawn_opts(Options));
do_spawn(GenMod, _, Mod, Args, Options) ->
Time = timeout(Options),
proc_lib:start(?MODULE, init_it,
[GenMod, self(), self, Mod, Args, Options],
Time,
spawn_opts(Options)).
do_spawn(GenMod, link, Name, Mod, Args, Options) ->
Time = timeout(Options),
proc_lib:start_link(?MODULE, init_it,
[GenMod, self(), self(), Name, Mod, Args, Options],
Time,
spawn_opts(Options));
do_spawn(GenMod, _, Name, Mod, Args, Options) ->
Time = timeout(Options),
proc_lib:start(?MODULE, init_it,
[GenMod, self(), self, Name, Mod, Args, Options],
Time,
spawn_opts(Options)).
%%-----------------------------------------------------------------
%% Initiate the new process.
%% Register the name using the Rfunc function
%% Calls the Mod:init/Args function.
%% Finally an acknowledge is sent to Parent and the main
%% loop is entered.
%%-----------------------------------------------------------------
init_it(GenMod, Starter, Parent, Mod, Args, Options) ->
init_it2(GenMod, Starter, Parent, self(), Mod, Args, Options).
init_it(GenMod, Starter, Parent, Name, Mod, Args, Options) ->
case name_register(Name) of
true ->
init_it2(GenMod, Starter, Parent, Name, Mod, Args, Options);
{false, Pid} ->
proc_lib:init_ack(Starter, {error, {already_started, Pid}})
end.
init_it2(GenMod, Starter, Parent, Name, Mod, Args, Options) ->
GenMod:init_it(Starter, Parent, Name, Mod, Args, Options).
%%-----------------------------------------------------------------
%% Makes a synchronous call to a generic process.
%% Request is sent to the Pid, and the response must be
%% {Tag, _, Reply}.
%%-----------------------------------------------------------------
%%% New call function which uses the new monitor BIF
%%% call(ServerId, Label, Request)
call(Process, Label, Request) ->
call(Process, Label, Request, ?default_timeout).
%% Local or remote by pid
call(Pid, Label, Request, Timeout)
when is_pid(Pid), Timeout =:= infinity;
is_pid(Pid), is_integer(Timeout), Timeout >= 0 ->
do_call(Pid, Label, Request, Timeout);
%% Local by name
call(Name, Label, Request, Timeout)
when is_atom(Name), Timeout =:= infinity;
is_atom(Name), is_integer(Timeout), Timeout >= 0 ->
case whereis(Name) of
Pid when is_pid(Pid) ->
do_call(Pid, Label, Request, Timeout);
undefined ->
exit(noproc)
end;
%% Global by name
call({global, _Name}=Process, Label, Request, Timeout)
when Timeout =:= infinity;
is_integer(Timeout), Timeout >= 0 ->
case where(Process) of
Pid when is_pid(Pid) ->
Node = node(Pid),
try do_call(Pid, Label, Request, Timeout)
catch
exit:{nodedown, Node} ->
%% A nodedown not yet detected by global,
%% pretend that it was.
exit(noproc)
end;
undefined ->
exit(noproc)
end;
%% Local by name in disguise
call({Name, Node}, Label, Request, Timeout)
when Node =:= node(), Timeout =:= infinity;
Node =:= node(), is_integer(Timeout), Timeout >= 0 ->
call(Name, Label, Request, Timeout);
%% Remote by name
call({_Name, Node}=Process, Label, Request, Timeout)
when is_atom(Node), Timeout =:= infinity;
is_atom(Node), is_integer(Timeout), Timeout >= 0 ->
if
node() =:= nonode@nohost ->
exit({nodedown, Node});
true ->
do_call(Process, Label, Request, Timeout)
end.
do_call(Process, Label, Request, Timeout) ->
%% We trust the arguments to be correct, i.e
%% Process is either a local or remote pid,
%% or a {Name, Node} tuple (of atoms) and in this
%% case this node (node()) _is_ distributed and Node =/= node().
Node = case Process of
{_S, N} when is_atom(N) ->
N;
_ when is_pid(Process) ->
node(Process)
end,
try erlang:monitor(process, Process) of
Mref ->
%% If the monitor/2 call failed to set up a connection to a
%% remote node, we don't want the '!' operator to attempt
%% to set up the connection again. (If the monitor/2 call
%% failed due to an expired timeout, '!' too would probably
%% have to wait for the timeout to expire.) Therefore,
%% use erlang:send/3 with the 'noconnect' option so that it
%% will fail immediately if there is no connection to the
%% remote node.
catch erlang:send(Process, {Label, {self(), Mref}, Request},
[noconnect]),
receive
{Mref, Reply} ->
erlang:demonitor(Mref, [flush]),
{ok, Reply};
{'DOWN', Mref, _, _, noconnection} ->
exit({nodedown, Node});
{'DOWN', Mref, _, _, Reason} ->
exit(Reason)
after Timeout ->
erlang:demonitor(Mref),
receive
{'DOWN', Mref, _, _, _} -> true
after 0 -> true
end,
exit(timeout)
end
catch
error:_ ->
%% Node (C/Java?) is not supporting the monitor.
%% The other possible case -- this node is not distributed
%% -- should have been handled earlier.
%% Do the best possible with monitor_node/2.
%% This code may hang indefinitely if the Process
%% does not exist. It is only used for featureweak remote nodes.
monitor_node(Node, true),
receive
{nodedown, Node} ->
monitor_node(Node, false),
exit({nodedown, Node})
after 0 ->
Tag = make_ref(),
Process ! {Label, {self(), Tag}, Request},
wait_resp(Node, Tag, Timeout)
end
end.
wait_resp(Node, Tag, Timeout) ->
receive
{Tag, Reply} ->
monitor_node(Node, false),
{ok, Reply};
{nodedown, Node} ->
monitor_node(Node, false),
exit({nodedown, Node})
after Timeout ->
monitor_node(Node, false),
exit(timeout)
end.
%%
%% Send a reply to the client.
%%
reply({To, Tag}, Reply) ->
Msg = {Tag, Reply},
try To ! Msg catch _:_ -> Msg end.
%%%-----------------------------------------------------------------
%%% Misc. functions.
%%%-----------------------------------------------------------------
where({global, Name}) -> global:safe_whereis_name(Name);
where({local, Name}) -> whereis(Name).
name_register({local, Name} = LN) ->
try register(Name, self()) of
true -> true
catch
error:_ ->
{false, where(LN)}
end;
name_register({global, Name} = GN) ->
case global:register_name(Name, self()) of
yes -> true;
no -> {false, where(GN)}
end.
timeout(Options) ->
case opt(timeout, Options) of
{ok, Time} ->
Time;
_ ->
infinity
end.
spawn_opts(Options) ->
case opt(spawn_opt, Options) of
{ok, Opts} ->
Opts;
_ ->
[]
end.
opt(Op, [{Op, Value}|_]) ->
{ok, Value};
opt(Op, [_|Options]) ->
opt(Op, Options);
opt(_, []) ->
false.
debug_options(Opts) ->
case opt(debug, Opts) of
{ok, Options} -> sys:debug_options(Options);
_ -> []
end.
format_status_header(TagLine, Pid) when is_pid(Pid) ->
lists:concat([TagLine, " ", pid_to_list(Pid)]);
format_status_header(TagLine, RegName) when is_atom(RegName) ->
lists:concat([TagLine, " ", RegName]);
format_status_header(TagLine, Name) ->
{TagLine, Name}.
