forked from KirinDave/gen_leader_revival
/
gen_leader.erl
1477 lines (1358 loc) · 59 KB
/
gen_leader.erl
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%%% ``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 via the world wide web 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.
%%%
%%% The Initial Developer of the Original Code is Ericsson Utvecklings AB.
%%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
%%% AB. All Rights Reserved.''
%%%
%%%
%%% $Id: gen_leader.erl,v 1.4 2008/09/19 07:40:15 hanssv Exp $
%%%
%%% @author Hans Svensson <hanssv@chalmers.se>
%%% @author Thomas Arts <thomas.arts@ituniv.se>
%%% @author Ulf Wiger <ulf.wiger@ericsson.com>
%%% @author (contributor: Serge Aleynikov <saleyn@gmail.com>)
%%%
%%% @doc Leader election behavior.
%%% <p>This application implements a leader election behavior modeled after
%%% gen_server. This behavior intends to make it reasonably
%%% straightforward to implement a fully distributed server with
%%% master-slave semantics.</p>
%%% <p>The gen_leader behavior supports nearly everything that gen_server
%%% does (some functions, such as multicall() and the internal timeout,
%%% have been removed), and adds a few callbacks and API functions to
%%% support leader election etc.</p>
%%% <p>Also included is an example program, a global dictionary, based
%%% on the modules gen_leader and dict. The callback implementing the
%%% global dictionary is called 'test_cb', for no particularly logical
%%% reason.</p>
%%% <p><b>New version:</b> The internal leader election algorithm was faulty
%%% and has been replaced with a new version based on a different leader
%%% election algorithm. As a consequence of this the query functions
%%% <tt>alive</tt> and <tt>down</tt> can no longer be provided.
%%% The new algorithm also make use of an incarnation parameter, by
%%% default written to disk in the function <tt>incarnation</tt>. This
%%% implies that only one <tt>gen_leader</tt> per node is permitted, if
%%% used in a diskless environment, <tt>incarnation</tt> must be adapted.
%%% </p>
%%% <p>
%%% Modifications contributed by Serge Aleynikov:
%%% <ol>
%%% <li>Added configurable startup options (see leader_options() type)</li>
%%% <li>Implemented handle_DOWN/3 callback with propagation of the
%%% leader's state via broadcast to all connected candidates.</li>
%%% <li>Fixed population of the #election.down member so that down/1 query
%%% can be used in the behavior's implementation</li>
%%% <li>Rewrote implementation of the tau timer to prevent the leader
%%% looping on the timer timeout event when all candidates are connected.</li>
%%% </ol>
%%% </p>
%%% @end
%%%
%%%
-module(gen_leader).
%% Time between rounds of query from the leader
-define(TAU,5000).
-export([start/6,
start_link/6,
leader_call/2, leader_call/3, leader_cast/2,
call/2, call/3, cast/2,
reply/2]).
%% Query functions
-export([alive/1,
down/1,
candidates/1,
workers/1,
broadcast/3,
leader_node/1]).
-export([system_continue/3,
system_terminate/4,
system_code_change/4,
format_status/2,
worker_announce/2
]).
-export([behaviour_info/1]).
%% Internal exports
-export([init_it/6,
print_event/3
]).
%% Notification control of candidate membership changes. `all'
%% means that returns from the handle_DOWN/3 and elected/3 leader's events
%% will be broadcast to all candidates.
-type bcast_type() :: 'all' | 'sender'.
-type option() :: {'workers', Workers::[node()]}
| {'vardir', Dir::string()}
| {'bcast_type', Type::bcast_type()}
| {'heartbeat', Seconds::integer()}.
-type options() :: [option()].
-type status() :: 'elec1' | 'elec2' | 'wait' | 'joining' | 'worker' |
'waiting_worker' | 'norm'.
%% A locally registered name
-type name() :: atom().
%% A monitor ref
-type mon_ref() :: reference().
-type server_ref() :: name() | {name(),node()} | {global,name()} | pid().
%% Incarnation number
-type incarn() :: non_neg_integer().
%% Logical clock
-type lclock() :: non_neg_integer().
%% Node priority in the election
-type priority() :: integer().
%% Election id
-type elid() :: {priority(), incarn(), lclock()}.
%% See gen_server.
-type caller_ref() :: {pid(), reference()}.
%% Opaque state of the gen_leader behaviour.
-record(election, {
leader = none :: 'none' | pid(),
previous_leader = none :: 'none' | pid(),
name :: name(),
leadernode = none :: node(),
candidate_nodes = [] :: [node()],
worker_nodes = [] :: [node()],
down = [] :: [node()],
monitored = [] :: [{mon_ref(), node()}],
buffered = [] :: [{reference(),caller_ref()}],
seed_node = none :: 'none' | node(),
status :: status(),
elid :: elid(),
acks = [] :: [node()],
work_down = [] :: [node()],
cand_timer_int :: integer(),
cand_timer :: term(),
pendack :: node(),
incarn :: incarn(),
nextel :: integer(),
%% all | one. When `all' each election event
%% will be broadcast to all candidate nodes.
bcast_type :: bcast_type()
}).
-record(server, {
parent,
mod,
state,
monitor_proc = spawn_monitor_proc(),
debug
}).
%%% ---------------------------------------------------
%%% Interface functions.
%%% ---------------------------------------------------
-spec behaviour_info(atom()) -> 'undefined' | [{atom(), arity()}].
behaviour_info(callbacks) ->
[{init,1},
{elected,3},
{surrendered,3},
{handle_leader_call,4},
{handle_leader_cast,3},
{from_leader,3},
{handle_call,4},
{handle_cast,3},
{handle_DOWN,3},
{handle_info,2},
{terminate,2},
{code_change,4}];
behaviour_info(_Other) ->
undefined.
-type start_ret() :: {'ok', pid()} | {'error', term()}.
%% @doc Starts a gen_leader process without linking to the parent.
%% @see start_link/6
-spec start(Name::atom(), CandidateNodes::[node()], OptArgs::options(),
Mod::module(), Arg::term(), Options::list()) -> start_ret().
start(Name, CandidateNodes, OptArgs, Mod, Arg, Options)
when is_atom(Name), is_list(CandidateNodes), is_list(OptArgs) ->
gen:start(?MODULE, nolink, {local,Name},
Mod, {CandidateNodes, OptArgs, Arg}, Options).
%% @doc Starts a gen_leader process.
%% <table>
%% <tr><td>Name</td><td>The locally registered name of the process</td></tr>
%% <tr><td>CandidateNodes</td><td>The names of nodes capable of assuming
%% a leadership role</td></tr>
%% <tr><td valign="top">OptArgs</td>
%% <td>Optional arguments given to `gen_leader'.
%% <du>
%% <dl>{workers, Workers}</dl>
%% <dd>The names of nodes that will be part of the "cluster",
%% but cannot ever assume a leadership role. Default: [].</dd>
%% <dl>{vardir, Dir}</dl>
%% <dd>Directory name used to store candidate's incarnation cookie.
%% Default: "."</dd>
%% <dl>{bcast_type, Type}</dl>
%% <dd>When `Type' is 'all' each election event (when a new
%% candidate becomes visible to the leader) will be broadcast
%% to all live candidate nodes. Each candidate will get
%% a from_leader/3 callback. When `Type' is `sender', only
%% the newly registered candidate will get the surrendered/3
%% callback. Default: `sender'.</dd>
%% <dl>{heartbeat, Seconds}</dl>
%% <dd>Heartbeat timeout value used to send ping messages to inactive
%% candidate nodes.</dd>
%% </du>
%% </td></tr>
%% <tr><td>Mod</td><td>The name of the callback module</td></tr>
%% <tr><td>Arg</td><td>Argument passed on to <code>Mod:init/1</code></td></tr>
%% <tr><td>Options</td><td>Same as gen_server's Options</td></tr>
%% </table>
%%
%% <p>The list of candidates needs to be known from the start. Workers
%% could potentially be added at runtime, but no functionality to do
%% this is provided by this version.</p>
%% @end
-spec start_link(Name::atom(), CandidateNodes::[node()], OptArgs::options(),
Mod::module(), Arg::term(), Options::list()) -> start_ret().
start_link(Name, CandidateNodes, OptArgs, Mod, Arg, Options)
when is_atom(Name), is_list(CandidateNodes), is_list(OptArgs) ->
gen:start(?MODULE, link, {local,Name},
Mod, {CandidateNodes, OptArgs, Arg}, Options).
%% Query functions to be used from the callback module
%% @doc Returns list of alive nodes.
-spec alive(#election{}) -> [node()].
alive(E) ->
candidates(E) -- down(E).
%% @doc Returns list of down nodes.
-spec down(#election{}) -> [node()].
down(#election{down = Down}) ->
Down.
%% @doc Returns the current leader node.
-spec leader_node(#election{}) -> node() | 'none'.
leader_node(#election{leadernode=Leader}) ->
Leader.
%% @doc Returns a list of known candidates.
-spec candidates(#election{}) -> [node()].
candidates(#election{candidate_nodes = Cands}) ->
Cands.
%% @doc Returns a list of known workers.
-spec workers(#election{}) -> [node()].
workers(#election{worker_nodes = Workers}) ->
Workers.
%% Used by dynamically added workers.
%% @hidden
worker_announce(Name, Pid) ->
Name ! {add_worker, Pid},
Name ! {heartbeat, Pid}.
%%
%% Make a call to a generic server.
%% If the server is located at another node, that node will
%% be monitored.
%% If the client is trapping exits and is linked server termination
%% is handled here (? Shall we do that here (or rely on timeouts) ?).
%%
%% @doc Equivalent to <code>gen_server:call/2</code>, but with a slightly
%% different exit reason if something goes wrong. This function calls
%% the <code>gen_leader</code> process exactly as if it were a gen_server
%% (which, for practical purposes, it is.)
%% @end
-spec call(server_ref(), term()) -> term().
call(Name, Request) ->
case catch gen:call(Name, '$gen_call', Request) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, local_call, [Name, Request]}})
end.
%% @doc Equivalent to <code>gen_server:call/3</code>, but with a slightly
%% different exit reason if something goes wrong. This function calls
%% the <code>gen_leader</code> process exactly as if it were a gen_server
%% (which, for practical purposes, it is.)
%% @end
-spec call(server_ref(), term(), integer()) -> term().
call(Name, Request, Timeout) ->
case catch gen:call(Name, '$gen_call', Request, Timeout) of
{ok,Res} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, local_call, [Name, Request, Timeout]}})
end.
%% @doc Makes a call (similar to <code>gen_server:call/2</code>) to the
%% leader. The call is forwarded via the local gen_leader instance, if
%% that one isn't actually the leader. The client will exit if the
%% leader dies while the request is outstanding.
%% <p>This function uses <code>gen:call/3</code>, and is subject to the
%% same default timeout as e.g. <code>gen_server:call/2</code>.</p>
%% @end
%%
-spec leader_call(Name::server_ref(), Request::term()) -> term().
leader_call(Name, Request) ->
case catch gen:call(Name, '$leader_call', Request) of
{ok,{leader,reply,Res}} ->
Res;
{ok,{error, leader_died}} ->
exit({leader_died, {?MODULE, leader_call, [Name, Request]}});
{'EXIT',Reason} ->
exit({Reason, {?MODULE, leader_call, [Name, Request]}})
end.
%% @doc Makes a call (similar to <code>gen_server:call/3</code>) to the
%% leader. The call is forwarded via the local gen_leader instance, if
%% that one isn't actually the leader. The client will exit if the
%% leader dies while the request is outstanding.
%% @end
%%
-spec leader_call(Name::server_ref(), Request::term(),
Timeout::integer()) -> term().
leader_call(Name, Request, Timeout) ->
case catch gen:call(Name, '$leader_call', Request, Timeout) of
{ok,{leader,reply,Res}} ->
Res;
{'EXIT',Reason} ->
exit({Reason, {?MODULE, leader_call, [Name, Request, Timeout]}})
end.
%% @equiv gen_server:cast/2
-spec cast(Name::name()|pid(), Request::term()) -> 'ok'.
cast(Name, Request) ->
catch do_cast('$gen_cast', Name, Request),
ok.
%% @doc Similar to <code>gen_server:cast/2</code> but will be forwarded to
%% the leader via the local gen_leader instance.
-spec leader_cast(Name::name()|pid(), Request::term()) -> 'ok'.
leader_cast(Name, Request) ->
catch do_cast('$leader_cast', Name, Request),
ok.
do_cast(Tag, Name, Request) when is_atom(Name) ->
Name ! {Tag, Request};
do_cast(Tag, Pid, Request) when is_pid(Pid) ->
Pid ! {Tag, Request}.
%% @equiv gen_server:reply/2
-spec reply(From::caller_ref(), Reply::term()) -> term().
reply({To, Tag}, Reply) ->
catch To ! {Tag, Reply}.
%%% ---------------------------------------------------
%%% 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.
%%% ---------------------------------------------------
%%% @hidden
init_it(Starter, Parent, {local, Name}, Mod, {CandidateNodes, Workers, Arg}, Options) ->
%% R13B passes {local, Name} instead of just Name
init_it(Starter, Parent, Name, Mod,
{CandidateNodes, Workers, Arg}, Options);
init_it(Starter, self, Name, Mod, {CandidateNodes, OptArgs, Arg}, Options) ->
init_it(Starter, self(), Name, Mod,
{CandidateNodes, OptArgs, Arg}, Options);
init_it(Starter,Parent,Name,Mod,{CandidateNodes,OptArgs,Arg},Options) ->
Workers = proplists:get_value(workers, OptArgs, []),
VarDir = proplists:get_value(vardir, OptArgs, "."),
Interval = proplists:get_value(heartbeat, OptArgs, ?TAU div 1000) * 1000,
BcastType = proplists:get_value(bcast_type,OptArgs, sender),
Seed = proplists:get_value(seed, OptArgs, none),
Debug = debug_options(Name, Options),
AmCandidate = case lists:member(node(), CandidateNodes) of
true -> true;
false ->
case lists:member(node(), Workers) of
true -> false;
false ->
Seed =/= none
end
end,
Election = #election{
candidate_nodes = CandidateNodes,
worker_nodes = Workers,
name = Name,
nextel = 0,
cand_timer_int = Interval,
bcast_type = BcastType
},
case {AmCandidate, lists:member(node(), Workers)} of
{false, false} ->
%% I am neither a candidate nor a worker - don't start this process
error_logger:warning_msg("~w not started - node is not a candidate/worker\n", [Name]),
proc_lib:init_ack(Starter, ignore),
exit(normal);
_ ->
ok
end,
case {catch Mod:init(Arg), AmCandidate, Seed =/= none} of
{{stop, Reason},_,_} ->
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
{ignore,_,_} ->
proc_lib:init_ack(Starter, ignore),
exit(normal);
{{'EXIT', Reason},_,_} ->
proc_lib:init_ack(Starter, {error, Reason}),
exit(Reason);
{{ok, State}, true, false} ->
Server = #server{parent = Parent,mod = Mod,
state = State,debug = Debug},
Incarn = incarnation(VarDir, Name, node()),
NewE = startStage1(Election#election{incarn = Incarn}, Server),
proc_lib:init_ack(Starter, {ok, self()}),
%% handle the case where there's only one candidate worker and we can't
%% rely on DOWN messages to trigger the elected() call because we never get
%% a DOWN for ourselves
case CandidateNodes =:= [node()] of
true ->
%% there's only one candidate leader; us
hasBecomeLeader(NewE,Server,{init});
false ->
%% more than one candidate worker, continue as normal
safe_loop(#server{parent = Parent,mod = Mod,
state = State,debug = Debug},
candidate, NewE,{init})
end;
{{ok, State}, true, true} ->
Server = #server{parent = Parent,mod = Mod,
state = State,debug = Debug},
Incarn = incarnation(VarDir, Name, node()),
NewE1 = Election#election{incarn = Incarn, seed_node = Seed},
NewE = joinCluster(NewE1, Server),
proc_lib:init_ack(Starter, {ok, self()}),
safe_loop(Server, candidate_joining, NewE, {init});
{{ok, State}, false, HasSeed} ->
proc_lib:init_ack(Starter, {ok, self()}),
Candidates = case HasSeed of
true ->
{ok, C} = call({Name, Seed}, get_candidates),
C;
false -> CandidateNodes
end,
case lists:member(node(), Workers) of
true ->
rpc:multicall(Candidates, gen_leader,
worker_announce, [Name, node(self())]);
false -> nop
end,
safe_loop(#server{parent = Parent,mod = Mod,
state = State,debug = Debug},
waiting_worker, Election,{init});
{Else,_,_} ->
Error = {bad_return_value, Else},
proc_lib:init_ack(Starter, {error, Error}),
exit(Error)
end.
%%% ---------------------------------------------------
%%% The MAIN loops.
%%% ---------------------------------------------------
safe_loop(#server{mod = Mod, state = State} = Server, Role,
#election{name = Name} = E, _PrevMsg) ->
receive
{system, From, Req} ->
#server{parent = Parent, debug = Debug} = Server,
sys:handle_system_msg(Req, From, Parent, ?MODULE, Debug,
[safe, Server, Role, E]);
{'EXIT', _, Reason} = Msg ->
terminate(Reason, Msg, Server, Role, E);
{update_candidates,_,_,_} = Msg ->
safe_loop(Server,Role,E,Msg);
{halt,T,From} = Msg ->
NewE = halting(E,T,From,Server),
From ! {ackLeader,T,self()},
safe_loop(Server,Role,NewE,Msg);
{hasLeader,Ldr,T,_} = Msg when Role == candidate_joining ->
NewE1 = mon_node(E,Ldr,Server),
NewE = NewE1#election{elid = T, leadernode = node(Ldr)},
Ldr ! {isLeader, T, self()},
safe_loop(Server,Role,NewE,Msg);
{hasLeader,Ldr,T,_} = Msg ->
NewE1 = mon_node(E,Ldr,Server),
case ( (E#election.status == elec2) and (E#election.acks /= []) ) of
true ->
lists:foreach(
fun(Node) ->
{Name,Node} ! {hasLeader,Ldr,T,self()}
end,E#election.acks);
false ->
ok
end,
NewE = NewE1#election{elid = T,
status = wait,
leadernode = node(Ldr),
down = E#election.down -- [node(Ldr)],
acks = []},
Ldr ! {isLeader,T,self()},
safe_loop(Server,Role,NewE,Msg);
{isLeader,T,From} = Msg ->
From ! {notLeader,T,self()},
safe_loop(Server,Role,E,Msg);
{notLeader,T,_} = Msg when Role == candidate_joining ->
NewE = case E#election.elid == T of
true ->
joinCluster(E, Server);
false ->
E
end,
safe_loop(Server,Role,NewE,Msg);
{notLeader,T,_} = Msg ->
NewE =
case ((E#election.status == wait) and (E#election.elid == T)) of
true ->
startStage1(E, Server);
false ->
E
end,
safe_loop(Server,Role,NewE,Msg);
{ackLeader,T,From} = Msg ->
NewE =
case ( (E#election.status == elec2) and (E#election.elid == T)
and (E#election.pendack == node(From)) ) of
true ->
continStage2(
E#election{acks = [node(From)|E#election.acks]},
Server);
false ->
E
end,
hasBecomeLeader(NewE,Server,Msg);
{ldr,Synch,T,_,_,From} = Msg when Role == waiting_worker ->
case ( (T == E#election.elid)
and (node(From) == E#election.leadernode)) of
true ->
NewE = E#election{ leader = From, status = worker },
{ok,NewState} = Mod:surrendered(State,Synch,NewE),
loop(Server#server{state = NewState},worker,NewE,Msg);
false ->
%% This should be a VERY special case...
%% But doing nothing is the right thing!
%% A DOWN message should arrive to solve this situation
safe_loop(Server,Role,E,Msg)
end;
{ldr,Synch,T,Workers,Candidates,From} = Msg ->
case ( ( (E#election.status == wait) or (E#election.status == joining) )
and (E#election.elid == T) ) of
true ->
timer:cancel(E#election.cand_timer),
NewE1 = mon_node(E, From, Server),
NewE2 = NewE1#election{leader = From,
leadernode = node(From),
previous_leader = E#election.leader,
worker_nodes = Workers,
candidate_nodes = Candidates,
status = norm,
cand_timer=undefined},
NewE = case Role == candidate_joining of
true ->
mon_nodes(NewE2, lesser(node(),candidates(NewE2)),Server);
false -> NewE2
end,
{ok,NewState} = Mod:surrendered(State,Synch,NewE),
loop(Server#server{state = NewState},surrendered,NewE,Msg);
false ->
safe_loop(Server,Role,E,Msg)
end;
{normQ,T,From} = Msg ->
NewE =
case ( (E#election.status == elec1)
or ( (E#election.status == wait)
and (E#election.elid == T) ) ) of
true ->
NE = halting(E,T,From,Server),
From ! {notNorm,T,self()},
NE;
false ->
E
end,
safe_loop(Server,Role,NewE,Msg);
{notNorm,_,_} = Msg ->
safe_loop(Server,Role,E,Msg);
{workerAlive,T,From} = Msg ->
NewE =
case E#election.leadernode == none of
true ->
%% We should initiate activation,
%% monitor the possible leader!
NE = mon_node(E#election{leadernode = node(From),
elid = T},
From, Server),
From ! {workerIsAlive,T,self()},
NE;
false ->
%% We should acutally ignore this, the present activation
%% will complete or abort first...
E
end,
safe_loop(Server,Role,NewE,Msg);
{workerIsAlive,_,_} = Msg ->
%% If this happens, the activation process should abort
%% This process is no longer the leader!
%% The sender will notice this via a DOWN message
safe_loop(Server,Role,E,Msg);
{heartbeat, _Node} = Msg ->
safe_loop(Server,Role,E,Msg);
{candidate_timer} = Msg ->
NewE =
case E#election.down of
[] ->
timer:cancel(E#election.cand_timer),
E#election{cand_timer = undefined};
Down ->
%% Some of potential master candidate nodes are down.
%% Try to wake them up
F = fun(N) ->
{E#election.name, N} ! {heartbeat, node()}
end,
[F(N) || N <- Down, {ok, up} =/= net_kernel:node_info(N, state)],
E
end,
safe_loop(Server,Role,NewE,Msg);
{ldr, 'DOWN', Node} = Msg when Role == waiting_worker ->
NewE =
case Node == E#election.leadernode of
true ->
E#election{leader = none, leadernode = none,
previous_leader = E#election.leader,
status = waiting_worker,
monitored = []};
false ->
E
end,
safe_loop(Server, Role, NewE,Msg);
{ldr, 'DOWN', Node} = Msg when Role == candidate_joining ->
Ldr = E#election.leadernode,
Seed = E#election.seed_node,
case Node of
Seed ->
case net_adm:ping(Ldr) of
pong -> noop;
pang ->
terminate(seed_nodes_down, Msg, Server, Role, E)
end;
Ldr ->
case net_adm:ping(Seed) of
pong ->
NewE = joinCluster(E, Server),
safe_loop(Server, Role, NewE, Msg);
pang ->
terminate(seed_nodes_down, Msg, Server, Role, E)
end
end;
{ldr, 'DOWN', Node} = Msg ->
NewMon = lists:keydelete(Node, 2, E#election.monitored),
NewE =
case lists:member(Node,E#election.candidate_nodes) of
true ->
NewDown = [Node | E#election.down],
E1 = E#election{down = NewDown, monitored = NewMon},
case ( pos(Node,E#election.candidate_nodes) <
pos(node(),E#election.candidate_nodes) ) of
true ->
Lesser = lesser(node(),E#election.candidate_nodes),
LesserIsSubset = (Lesser -- NewDown) == [],
case ((E#election.status == wait)
and (Node == E#election.leadernode)) of
true ->
startStage1(E1, Server);
false ->
case ((E#election.status == elec1) and
LesserIsSubset) of
true ->
startStage2(
E1#election{down = Lesser},
Server);
false ->
E1
end
end;
false ->
case ( (E#election.status == elec2)
and (Node == E#election.pendack) ) of
true ->
continStage2(E1, Server);
false ->
case ( (E#election.status == wait)
and (Node == E#election.leadernode)) of
true ->
startStage1(E1, Server);
false ->
E1
end
end
end
end,
hasBecomeLeader(NewE,Server,Msg)
end.
loop(#server{parent = Parent,
mod = Mod,
state = State,
debug = Debug} = Server, Role,
#election{name = Name} = E, _PrevMsg) ->
receive
Msg ->
case Msg of
{system, From, Req} ->
sys:handle_system_msg(Req, From, Parent, ?MODULE, Debug,
[normal, Server, Role, E]);
{'EXIT', Parent, Reason} ->
terminate(Reason, Msg, Server, Role, E);
{join, From} ->
From ! {hasLeader,E#election.leader,E#election.elid,self()},
loop(Server,Role,E,Msg);
{update_candidates, T, Candidates, _From} ->
case E#election.elid == T of
true ->
NewE = E#election{candidate_nodes = Candidates},
loop(Server, Role, NewE, Msg);
false ->
loop(Server, Role, E, Msg)
end;
{halt,_,From} ->
From ! {hasLeader,E#election.leader,E#election.elid,self()},
loop(Server,Role,E,Msg);
{hasLeader,_,_,_} ->
loop(Server,Role,E,Msg);
{isLeader,T,From} ->
case (self() == E#election.leader) of
true ->
NewCandidates =
case lists:member(node(From), candidates(E)) of
true -> candidates(E);
false ->
NC = candidates(E) ++ [node(From)],
lists:foreach(
fun(Node) ->
{Name, Node} !
{update_candidates, E#election.elid,
NC, self()}
end, candidates(E) -- lists:flatten([node()],down(E))),
NC
end,
NewDown = E#election.down -- [node(From)],
NewE1 = mon_node(E#election{down = NewDown},
From, Server),
NewE = NewE1#election{candidate_nodes = NewCandidates},
NewState = call_elected(Mod, State, NewE, From),
loop(Server#server{state = NewState},Role,NewE,Msg);
false ->
From ! {notLeader,T,self()},
loop(Server,Role,E,Msg)
end;
{ackLeader,_,_} ->
loop(Server,Role,E,Msg);
{notLeader,_,_} ->
loop(Server,Role,E,Msg);
{ack,_,_} ->
loop(Server,Role,E,Msg);
{ldr,_,_,_,_} ->
loop(Server,Role,E,Msg);
{normQ,_,_} ->
loop(Server,Role,E,Msg);
{notNorm,T,From} ->
case ( (E#election.leader == self())
and (E#election.elid == T) ) of
true ->
NewDown = E#election.down -- [node(From)],
NewE = mon_node(E#election{down = NewDown},
From,Server),
NewState = call_elected(Mod, State, NewE, From),
loop(Server#server{state = NewState},Role,NewE,Msg);
false ->
loop(Server,Role,E,Msg)
end;
{workerAlive,_,_} ->
%% Do nothing if we get this from a new leader
%% We will soon notice that the prev leader has died, and
%%get the same message again when we are back in safe_loop!
loop(Server,Role,E,Msg);
{activateWorker,_,_,_} ->
%% We ignore this, we are already active...
%% It must be an old message!
loop(Server,Role,E,Msg);
{workerIsAlive,T,From} ->
case ((T == E#election.elid) and (self() == E#election.leader)) of
true ->
NewDown = E#election.work_down -- [node(From)],
NewE = mon_node(E#election{work_down = NewDown},
From, Server),
NewState = call_elected(Mod,State,NewE,From),
loop(Server#server{state = NewState},Role,NewE,Msg);
false ->
loop(Server,Role,E,Msg)
end;
{heartbeat, _Node} ->
case (E#election.leader == self()) of
true ->
Candidates = E#election.down -- [lists:nth(1,E#election.candidate_nodes)],
lists:foreach(
fun(N) ->
Elid = E#election.elid,
{Name,N} ! {normQ,Elid,self()}
end,Candidates),
lists:foreach(
fun(N) ->
Elid = E#election.elid,
{Name,N} ! {workerAlive,Elid,self()}
end,E#election.work_down);
false ->
ok
end,
loop(Server,Role,E,Msg);
{candidate_timer} = Msg ->
NewE =
if E#election.down =:= [] orelse (Role =/= elected andalso E#election.leadernode =/= none) ->
timer:cancel(E#election.cand_timer),
E#election{cand_timer=undefined};
true ->
E
end,
%% This shouldn't happen in the leader - just ignore
loop(Server,Role,NewE,Msg);
{ldr, 'DOWN', Node} = Msg when Role == worker ->
case Node == E#election.leadernode of
true ->
NewE = E#election{ leader = none, leadernode = none,
status = waiting_worker,
monitored = []},
safe_loop(Server, waiting_worker, NewE,Msg);
false ->
loop(Server, Role, E,Msg)
end;
{ldr, 'DOWN', Node} = Msg ->
NewMon = lists:keydelete(Node, 2, E#election.monitored),
case lists:member(Node,E#election.candidate_nodes) of
true ->
NewDown = [Node | E#election.down],
E1 = E#election{down = NewDown, monitored = NewMon},
case (Node == E#election.leadernode) of
true ->
NewE = startStage1(E1, Server),
safe_loop(Server, candidate, NewE,Msg);
false when E#election.leadernode =:= node() ->
%% Serge: call handle_DOWN
{NewState, NewE} =
case (Server#server.mod):handle_DOWN(Node, Server#server.state, E1) of
{ok, NewState1} ->
{NewState1, E1};
{ok, Synch, NewState1} ->
{NewState1, broadcast({from_leader,Synch}, E1)}
end,
loop(Server#server{state=NewState}, Role, NewE, Msg);
false ->
loop(Server, Role, E1,Msg)
end;
false ->
%% I am the leader,
%% make sure the dead worker is in work_down.
E1 = E#election{
monitored = NewMon,
work_down = [Node |
(E#election.work_down -- [Node])]
},
loop(Server, Role, E1,Msg)
end;
{add_worker, WorkerNode} ->
case lists:member(WorkerNode, E#election.worker_nodes) of
false ->
{WNodes, DNodes} = {E#election.worker_nodes, E#election.work_down},
loop(Server, Role, E#election{worker_nodes=[WorkerNode|WNodes],
work_down=[WorkerNode|DNodes]},
Msg);
true -> % Redundancy, meet the mirror
loop(Server, Role, E, Msg)
end;
_Msg when Debug == [] ->
handle_msg(Msg, Server, Role, E);
_Msg ->
Debug1 = sys:handle_debug(Debug, {?MODULE, print_event},
E#election.name, {in, Msg}),
handle_msg(Msg, Server#server{debug = Debug1}, Role, E)
end
end.
%%-----------------------------------------------------------------
%% Callback functions for system messages handling.
%%-----------------------------------------------------------------
%% @hidden
system_continue(_Parent, _Debug, [safe, Server, Role, E]) ->
safe_loop(Server, Role, E,{});
system_continue(_Parent, _Debug, [normal, Server, Role, E]) ->
loop(Server, Role, E,{}).
%% @hidden
system_terminate(Reason, _Parent, _Debug, [_Mode, Server, Role, E]) ->
terminate(Reason, [], Server, Role, E).
%% @hidden
system_code_change([Mode, Server, Role, E], _Module, OldVsn, Extra) ->
#server{mod = Mod, state = State} = Server,
case catch Mod:code_change(OldVsn, State, E, Extra) of
{ok, NewState} ->
NewServer = Server#server{state = NewState},
{ok, [Mode, NewServer, Role, E]};
{ok, NewState, NewE} ->
NewServer = Server#server{state = NewState},
{ok, [Mode, NewServer, Role, NewE]};
Else -> Else
end.
%%-----------------------------------------------------------------
%% Format debug messages. Print them as the call-back module sees
%% them, not as the real erlang messages. Use trace for that.
%%-----------------------------------------------------------------
%% @hidden
print_event(Dev, {in, Msg}, Name) ->
case Msg of
{'$gen_call', {From, _Tag}, Call} ->
io:format(Dev, "*DBG* ~p got local call ~p from ~w~n",
[Name, Call, From]);
{'$leader_call', {From, _Tag}, Call} ->
io:format(Dev, "*DBG* ~p got global call ~p from ~w~n",
[Name, Call, From]);
{'$gen_cast', Cast} ->
io:format(Dev, "*DBG* ~p got local cast ~p~n",
[Name, Cast]);
{'$leader_cast', Cast} ->
io:format(Dev, "*DBG* ~p got global cast ~p~n",
[Name, Cast]);
_ ->
io:format(Dev, "*DBG* ~p got ~p~n", [Name, Msg])
end;
print_event(Dev, {out, Msg, To, State}, Name) ->
io:format(Dev, "*DBG* ~p sent ~p to ~w, new state ~w~n",
[Name, Msg, To, State]);
print_event(Dev, {noreply, State}, Name) ->
io:format(Dev, "*DBG* ~p new state ~w~n", [Name, State]);
print_event(Dev, Event, Name) ->
io:format(Dev, "*DBG* ~p dbg ~p~n", [Name, Event]).
handle_msg({'$leader_call', From, Request} = Msg,
#server{mod = Mod, state = State} = Server, elected = Role, E) ->
case catch Mod:handle_leader_call(Request, From, State, E) of
{reply, Reply, NState} ->
NewServer = reply(From, {leader,reply,Reply},
Server#server{state = NState}, Role, E),
loop(NewServer, Role, E,Msg);
{reply, Reply, Broadcast, NState} ->
NewE = broadcast({from_leader,Broadcast}, E),
NewServer = reply(From, {leader,reply,Reply},
Server#server{state = NState}, Role,
NewE),
loop(NewServer, Role, NewE,Msg);
{noreply, NState} = Reply ->
NewServer = handle_debug(Server#server{state = NState},
Role, E, Reply),
loop(NewServer, Role, E,Msg);
{stop, Reason, Reply, NState} ->
{'EXIT', R} =
(catch terminate(Reason, Msg,
Server#server{state = NState},
Role, E)),
reply(From, Reply),
exit(R);
Other ->