%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1997-2009. 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%
%%
%%----------------------------------------------------------------------
%% Purpose : Interface function to relay calls (esp. trace calls)
%% to processes on other nodes. Some of the calls
%% are conditionally relayed.
%%----------------------------------------------------------------------
-module(pman_relay).
%%-compile(export_all).
-export([start/1,
ok_to_trace/1,
trac/3]).
-include("assert.hrl").
%% --------------------------------------------------------------
%% DISTRIBUTION
%% --------------------------------------------------------------
%% (???) Process dictionary alert!!!
%%
%% Since we are not allowed to do erlang:trace/3 on remote
%% processe we create a help process at the remote node to
%% do the job for us
%% ---------------------------------------------------------------
start(P) when is_pid(P), node(P)/=node() ->
%% Remote supervision, relaying necessary
put(relay, spawn_link(node(P), pman_relay_server, init, [self()]));
start(_) ->
%% Local supervision, no relaying
ignore.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% ok_to_trace/1 - Tests wheter we can actually start tracing
%% a process.
%%
%% Arguments:
%% Pid Pid of the process to trace (on local or remote node)
%%
%% Returns
%% true If it is OK to trace the process
%% false If the process is already traced, or some other
%% condition prevents it from being traced.
ok_to_trace(Pid) when node(Pid) == node()->
%% Local trace, no relaying
case catch erlang:trace(Pid, false, [send]) of
1 ->
true;
_Otherwise ->
false
end;
ok_to_trace(Pid) ->
%% Remote trace, relaying necessary
PidRelay = get(relay),
PidRelay ! {ok_to_trace, self(), Pid},
receive
{ok_to_trace, PidRelay} ->
true;
{not_ok_to_trace, PidRelay} ->
false;
_Otherwise ->
?ALWAYS_ASSERT("Unexpected message from relay process")
after
5000 ->
false
end.
%% ---------------------------------------------------------------
%% Possibly send a request to do tracing to a remote node.
%% ---------------------------------------------------------------
trac(Pid, How, Flag) when node(Pid) == node() ->
%% Local trace, no relaying necessary
case catch erlang:trace(Pid, How, Flag) of
1 -> ok;
_ -> pman_win:format("** Illegal trace request ** \n", [])
end;
trac(Pid, How, Flag) ->
%% Remote trace, relaying necessary
get(relay) ! {self(), erlang, trace, [Pid, How, Flag]}.
