%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2011. 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%
%%
%%
%% This module implements (as a process) the state machine documented
%% in Appendix A of RFC 3539.
%%
-module(diameter_watchdog).
-behaviour(gen_server).
%% towards diameter_service
-export([start/2]).
%% gen_server callbacks
-export([init/1,
handle_call/3,
handle_cast/2,
handle_info/2,
terminate/2,
code_change/3]).
%% diameter_watchdog_sup callback
-export([start_link/1]).
-include_lib("diameter/include/diameter.hrl").
-include("diameter_internal.hrl").
-define(DEFAULT_TW_INIT, 30000). %% RFC 3539 ch 3.4.1
-record(watchdog,
{%% PCB - Peer Control Block; see RFC 3539, Appendix A
status = initial :: initial | okay | suspect | down | reopen,
pending = false :: boolean(),
tw :: 6000..16#FFFFFFFF | {module(), atom(), list()},
%% {M,F,A} -> integer() >= 0
num_dwa = 0 :: -1 | non_neg_integer(),
%% number of DWAs received during reopen
%% end PCB
parent = self() :: pid(),
transport :: pid(),
tref :: reference(), %% reference for current watchdog timer
message_data}). %% term passed into diameter_service with message
%% start/2
start({_,_} = Type, T) ->
{ok, Pid} = diameter_watchdog_sup:start_child({Type, self(), T}),
Pid.
start_link(T) ->
{ok, _} = proc_lib:start_link(?MODULE,
init,
[T],
infinity,
diameter_lib:spawn_opts(server, [])).
%% ===========================================================================
%% ===========================================================================
%% init/1
init(T) ->
proc_lib:init_ack({ok, self()}),
gen_server:enter_loop(?MODULE, [], i(T)).
i({T, Pid, {ConnT, Opts, SvcName, #diameter_service{applications = Apps,
capabilities = Caps}
= Svc}}) ->
{M,S,U} = now(),
random:seed(M,S,U),
putr(restart, {T, Opts, Svc}), %% save seeing it in trace
putr(dwr, dwr(Caps)), %%
#watchdog{parent = monitor(Pid),
transport = monitor(diameter_peer_fsm:start(T, Opts, Svc)),
tw = proplists:get_value(watchdog_timer,
Opts,
?DEFAULT_TW_INIT),
message_data = {ConnT, SvcName, Apps}}.
%% handle_call/3
handle_call(_, _, State) ->
{reply, nok, State}.
%% handle_cast/2
handle_cast(_, State) ->
{noreply, State}.
%% handle_info/2
handle_info(T, State) ->
case transition(T, State) of
ok ->
{noreply, State};
#watchdog{status = X} = S ->
?LOGC(X =/= State#watchdog.status, transition, X),
{noreply, S};
stop ->
?LOG(stop, T),
{stop, {shutdown, T}, State}
end.
%% terminate/2
terminate(_, _) ->
ok.
%% code_change/3
code_change(_, State, _) ->
{ok, State}.
%% ===========================================================================
%% ===========================================================================
%% transition/2
%%
%% The state transitions documented here are extracted from RFC 3539,
%% the commentary is ours.
%% Service or watchdog is telling the watchdog of an accepting
%% transport to die after reconnect_timer expiry or reestablished
%% connection (in another transport process) respectively.
transition(close, #watchdog{status = down}) ->
{{accept, _}, _, _} = getr(restart), %% assert
stop;
transition(close, #watchdog{}) ->
ok;
%% Service is asking for the peer to be taken down gracefully.
transition({shutdown, Pid}, #watchdog{parent = Pid,
transport = undefined,
status = S}) ->
down = S, %% sanity check
stop;
transition({shutdown = T, Pid}, #watchdog{parent = Pid,
transport = TPid}) ->
TPid ! {T, self()},
ok;
%% Parent process has died,
transition({'DOWN', _, process, Pid, _Reason},
#watchdog{parent = Pid}) ->
stop;
%% Transport has accepted a connection.
transition({accepted = T, TPid}, #watchdog{transport = TPid,
parent = Pid}) ->
Pid ! {T, self(), TPid},
ok;
%% Transport is telling us that its impending death isn't failure.
transition({close, TPid, _Reason}, #watchdog{transport = TPid}) ->
stop;
%% STATE Event Actions New State
%% ===== ------ ------- ----------
%% INITIAL Connection up SetWatchdog() OKAY
%% By construction, the watchdog timer isn't set until we move into
%% state okay as the result of the Peer State Machine reaching the
%% Open state.
%%
%% If we're accepting then we may be resuming a connection that went
%% down in another watchdog process, in which case this is the
%% transition below, from down to reopen. That is, it's not until we
%% know the identity of the peer (ie. now) that we know that we're in
%% state down rather than initial.
transition({open, TPid, Hosts, T} = Open,
#watchdog{transport = TPid,
status = initial,
parent = Pid}
= S) ->
case okay(getr(restart), Hosts) of
okay ->
open(Pid, {TPid, T}),
set_watchdog(S#watchdog{status = okay});
reopen ->
transition(Open, S#watchdog{status = down})
end;
%% DOWN Connection up NumDWA = 0
%% SendWatchdog()
%% SetWatchdog()
%% Pending = TRUE REOPEN
transition({open = P, TPid, _Hosts, T},
#watchdog{transport = TPid,
status = down}
= S) ->
%% Store the info we need to notify the parent to reopen the
%% connection after the requisite DWA's are received, at which
%% time we eraser(open).
putr(P, {TPid, T}),
set_watchdog(send_watchdog(S#watchdog{status = reopen,
num_dwa = 0}));
%% OKAY Connection down CloseConnection()
%% Failover()
%% SetWatchdog() DOWN
%% SUSPECT Connection down CloseConnection()
%% SetWatchdog() DOWN
%% REOPEN Connection down CloseConnection()
%% SetWatchdog() DOWN
transition({'DOWN', _, process, TPid, _},
#watchdog{transport = TPid,
status = initial}) ->
stop;
transition({'DOWN', _, process, Pid, _},
#watchdog{transport = Pid}
= S) ->
failover(S),
close(S),
set_watchdog(S#watchdog{status = down,
pending = false,
transport = undefined});
%% Any outstanding pending (or other messages from the transport) will
%% have arrived before 'DOWN' since the message comes from the same
%% process. Note that we could also get this message in the initial
%% state.
%% Incoming message.
transition({recv, TPid, Name, Pkt}, #watchdog{transport = TPid} = S) ->
recv(Name, Pkt, S);
%% Current watchdog has timed out.
transition({timeout, TRef, tw}, #watchdog{tref = TRef} = S) ->
set_watchdog(timeout(S));
%% Timer was canceled after message was already sent.
transition({timeout, _, tw}, #watchdog{}) ->
ok;
%% State query.
transition({state, Pid}, #watchdog{status = S}) ->
Pid ! {self(), S},
ok.
%% ===========================================================================
monitor(Pid) ->
erlang:monitor(process, Pid),
Pid.
putr(Key, Val) ->
put({?MODULE, Key}, Val).
getr(Key) ->
get({?MODULE, Key}).
eraser(Key) ->
erase({?MODULE, Key}).
%% encode/1
encode(Msg) ->
#diameter_packet{bin = Bin} = diameter_codec:encode(?BASE, Msg),
Bin.
%% okay/2
okay({{accept, Ref}, _, _}, Hosts) ->
T = {?MODULE, connection, Ref, Hosts},
diameter_reg:add(T),
okay(diameter_reg:match(T));
%% Register before matching so that at least one of two registering
%% processes will match the other. (Which can't happen as long as
%% diameter_peer_fsm guarantees at most one open connection to the same
%% peer.)
okay({{connect, _}, _, _}, _) ->
okay.
%% The peer hasn't been connected recently ...
okay([{_,P}]) ->
P = self(), %% assert
okay;
%% ... or it has.
okay(C) ->
[_|_] = [P ! close || {_,P} <- C, self() /= P],
reopen.
%% set_watchdog/1
set_watchdog(#watchdog{tw = TwInit,
tref = TRef}
= S) ->
cancel(TRef),
S#watchdog{tref = erlang:start_timer(tw(TwInit), self(), tw)}.
cancel(undefined) ->
ok;
cancel(TRef) ->
erlang:cancel_timer(TRef).
tw(T)
when is_integer(T), T >= 6000 ->
T - 2000 + (random:uniform(4001) - 1); %% RFC3539 jitter of +/- 2 sec.
tw({M,F,A}) ->
apply(M,F,A).
%% open/2
open(Pid, {_,_} = T) ->
Pid ! {connection_up, self(), T}.
%% failover/1
failover(#watchdog{status = okay,
parent = Pid}) ->
Pid ! {connection_down, self()};
failover(_) ->
ok.
%% close/1
close(#watchdog{status = down}) ->
ok;
close(#watchdog{parent = Pid}) ->
{{T, _}, _, _} = getr(restart),
T == accept andalso (Pid ! {close, self()}).
%% send_watchdog/1
send_watchdog(#watchdog{pending = false,
transport = TPid}
= S) ->
TPid ! {send, encode(getr(dwr))},
?LOG(send, 'DWR'),
S#watchdog{pending = true}.
%% recv/3
recv(Name, Pkt, S) ->
try rcv(Name, S) of
#watchdog{} = NS ->
rcv(Name, Pkt, S),
NS
catch
throw: {?MODULE, throwaway, #watchdog{} = NS} ->
NS
end.
%% rcv/3
rcv(N, _, _)
when N == 'CER';
N == 'CEA';
N == 'DWR';
N == 'DWA';
N == 'DPR';
N == 'DPA' ->
false;
rcv(_, Pkt, #watchdog{transport = TPid,
message_data = T}) ->
diameter_service:receive_message(TPid, Pkt, T).
throwaway(S) ->
throw({?MODULE, throwaway, S}).
%% rcv/2
%% INITIAL Receive DWA Pending = FALSE
%% Throwaway() INITIAL
%% INITIAL Receive non-DWA Throwaway() INITIAL
rcv('DWA', #watchdog{status = initial} = S) ->
throwaway(S#watchdog{pending = false});
rcv(_, #watchdog{status = initial} = S) ->
throwaway(S);
%% DOWN Receive DWA Pending = FALSE
%% Throwaway() DOWN
%% DOWN Receive non-DWA Throwaway() DOWN
rcv('DWA', #watchdog{status = down} = S) ->
throwaway(S#watchdog{pending = false});
rcv(_, #watchdog{status = down} = S) ->
throwaway(S);
%% OKAY Receive DWA Pending = FALSE
%% SetWatchdog() OKAY
%% OKAY Receive non-DWA SetWatchdog() OKAY
rcv('DWA', #watchdog{status = okay} = S) ->
set_watchdog(S#watchdog{pending = false});
rcv(_, #watchdog{status = okay} = S) ->
set_watchdog(S);
%% SUSPECT Receive DWA Pending = FALSE
%% Failback()
%% SetWatchdog() OKAY
%% SUSPECT Receive non-DWA Failback()
%% SetWatchdog() OKAY
rcv('DWA', #watchdog{status = suspect} = S) ->
failback(S),
set_watchdog(S#watchdog{status = okay,
pending = false});
rcv(_, #watchdog{status = suspect} = S) ->
failback(S),
set_watchdog(S#watchdog{status = okay});
%% REOPEN Receive DWA & Pending = FALSE
%% NumDWA == 2 NumDWA++
%% Failback() OKAY
rcv('DWA', #watchdog{status = reopen,
num_dwa = 2 = N,
parent = Pid}
= S) ->
open(Pid, eraser(open)),
S#watchdog{status = okay,
num_dwa = N+1,
pending = false};
%% REOPEN Receive DWA & Pending = FALSE
%% NumDWA < 2 NumDWA++ REOPEN
rcv('DWA', #watchdog{status = reopen,
num_dwa = N}
= S) ->
S#watchdog{num_dwa = N+1,
pending = false};
%% REOPEN Receive non-DWA Throwaway() REOPEN
rcv(_, #watchdog{status = reopen} = S) ->
throwaway(S).
%% failback/1
failback(#watchdog{parent = Pid}) ->
Pid ! {connection_up, self()}.
%% timeout/1
%%
%% The caller sets the watchdog on the return value.
%% OKAY Timer expires & SendWatchdog()
%% !Pending SetWatchdog()
%% Pending = TRUE OKAY
%% REOPEN Timer expires & SendWatchdog()
%% !Pending SetWatchdog()
%% Pending = TRUE REOPEN
timeout(#watchdog{status = T,
pending = false}
= S)
when T == okay;
T == reopen ->
send_watchdog(S);
%% OKAY Timer expires & Failover()
%% Pending SetWatchdog() SUSPECT
timeout(#watchdog{status = okay,
pending = true}
= S) ->
failover(S),
S#watchdog{status = suspect};
%% SUSPECT Timer expires CloseConnection()
%% SetWatchdog() DOWN
%% REOPEN Timer expires & CloseConnection()
%% Pending & SetWatchdog()
%% NumDWA < 0 DOWN
timeout(#watchdog{status = T,
pending = P,
num_dwa = N,
transport = TPid}
= S)
when T == suspect;
T == reopen, P, N < 0 ->
exit(TPid, shutdown),
close(S),
S#watchdog{status = down};
%% REOPEN Timer expires & NumDWA = -1
%% Pending & SetWatchdog()
%% NumDWA >= 0 REOPEN
timeout(#watchdog{status = reopen,
pending = true,
num_dwa = N}
= S)
when 0 =< N ->
S#watchdog{num_dwa = -1};
%% DOWN Timer expires AttemptOpen()
%% SetWatchdog() DOWN
%% INITIAL Timer expires AttemptOpen()
%% SetWatchdog() INITIAL
%% RFC 3539, 3.4.1:
%%
%% [5] While the connection is in the closed state, the AAA client MUST
%% NOT attempt to send further watchdog messages on the connection.
%% However, after the connection is closed, the AAA client continues
%% to periodically attempt to reopen the connection.
%%
%% The AAA client SHOULD wait for the transport layer to report
%% connection failure before attempting again, but MAY choose to
%% bound this wait time by the watchdog interval, Tw.
%% Don't bound, restarting the peer process only when the previous
%% process has died. We only need to handle state down since we start
%% the first watchdog when transitioning out of initial.
timeout(#watchdog{status = down} = S) ->
restart(S).
%% restart/1
restart(#watchdog{transport = undefined} = S) ->
restart(getr(restart), S);
restart(S) ->
S.
%% Only restart the transport in the connecting case. For an accepting
%% transport, we've registered the peer connection when leaving state
%% initial and this is used by a new accepting process to realize that
%% it's actually in state down rather then initial when receiving
%% notification of an open connection.
restart({{connect, _} = T, Opts, Svc}, #watchdog{parent = Pid} = S) ->
Pid ! {reconnect, self()},
S#watchdog{transport = monitor(diameter_peer_fsm:start(T, Opts, Svc))};
restart({{accept, _}, _, _}, S) ->
S.
%% Don't currently use Opts/Svc in the accept case but having them in
%% the process dictionary is helpful if the process dies unexpectedly.
%% dwr/1
dwr(#diameter_caps{origin_host = OH,
origin_realm = OR,
origin_state_id = OSI}) ->
['DWR', {'Origin-Host', OH},
{'Origin-Realm', OR},
{'Origin-State-Id', OSI}].
