--- /dev/null
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2010. 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(pg2_backport).
+
+-export([create/1, delete/1, join/2, leave/2]).
+-export([get_members/1, get_local_members/1]).
+-export([get_closest_pid/1, which_groups/0]).
+-export([start/0,start_link/0,init/1,handle_call/3,handle_cast/2,handle_info/2,
+ terminate/2]).
+
+%%% As of R13B03 monitors are used instead of links.
+
+%%%
+%%% Exported functions
+%%%
+
+-spec start_link() -> {'ok', pid()} | {'error', term()}.
+
+start_link() ->
+ gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+-spec start() -> {'ok', pid()} | {'error', term()}.
+
+start() ->
+ ensure_started().
+
+-spec create(term()) -> 'ok'.
+
+create(Name) ->
+ ensure_started(),
+ case ets:member(pg2_table, {group, Name}) of
+ false ->
+ global:trans({{?MODULE, Name}, self()},
+ fun() ->
+ gen_server:multi_call(?MODULE, {create, Name})
+ end),
+ ok;
+ true ->
+ ok
+ end.
+
+-type name() :: term().
+
+-spec delete(name()) -> 'ok'.
+
+delete(Name) ->
+ ensure_started(),
+ global:trans({{?MODULE, Name}, self()},
+ fun() ->
+ gen_server:multi_call(?MODULE, {delete, Name})
+ end),
+ ok.
+
+-spec join(name(), pid()) -> 'ok' | {'error', {'no_such_group', term()}}.
+
+join(Name, Pid) when is_pid(Pid) ->
+ ensure_started(),
+ case ets:member(pg2_table, {group, Name}) of
+ false ->
+ {error, {no_such_group, Name}};
+ true ->
+ global:trans({{?MODULE, Name}, self()},
+ fun() ->
+ gen_server:multi_call(?MODULE,
+ {join, Name, Pid})
+ end),
+ ok
+ end.
+
+-spec leave(name(), pid()) -> 'ok' | {'error', {'no_such_group', name()}}.
+
+leave(Name, Pid) when is_pid(Pid) ->
+ ensure_started(),
+ case ets:member(pg2_table, {group, Name}) of
+ false ->
+ {error, {no_such_group, Name}};
+ true ->
+ global:trans({{?MODULE, Name}, self()},
+ fun() ->
+ gen_server:multi_call(?MODULE,
+ {leave, Name, Pid})
+ end),
+ ok
+ end.
+
+-type get_members_ret() :: [pid()] | {'error', {'no_such_group', name()}}.
+
+-spec get_members(name()) -> get_members_ret().
+
+get_members(Name) ->
+ ensure_started(),
+ case ets:member(pg2_table, {group, Name}) of
+ true ->
+ group_members(Name);
+ false ->
+ {error, {no_such_group, Name}}
+ end.
+
+-spec get_local_members(name()) -> get_members_ret().
+
+get_local_members(Name) ->
+ ensure_started(),
+ case ets:member(pg2_table, {group, Name}) of
+ true ->
+ local_group_members(Name);
+ false ->
+ {error, {no_such_group, Name}}
+ end.
+
+-spec which_groups() -> [name()].
+
+which_groups() ->
+ ensure_started(),
+ all_groups().
+
+-type gcp_error_reason() :: {'no_process', term()} | {'no_such_group', term()}.
+
+-spec get_closest_pid(term()) -> pid() | {'error', gcp_error_reason()}.
+
+get_closest_pid(Name) ->
+ case get_local_members(Name) of
+ [Pid] ->
+ Pid;
+ [] ->
+ {_,_,X} = erlang:now(),
+ case get_members(Name) of
+ [] -> {error, {no_process, Name}};
+ Members ->
+ lists:nth((X rem length(Members))+1, Members)
+ end;
+ Members when is_list(Members) ->
+ {_,_,X} = erlang:now(),
+ lists:nth((X rem length(Members))+1, Members);
+ Else ->
+ Else
+ end.
+
+%%%
+%%% Callback functions from gen_server
+%%%
+
+-record(state, {}).
+
+-spec init([]) -> {'ok', #state{}}.
+
+init([]) ->
+ Ns = nodes(),
+ net_kernel:monitor_nodes(true),
+ lists:foreach(fun(N) ->
+ {?MODULE, N} ! {new_pg2, node()},
+ self() ! {nodeup, N}
+ end, Ns),
+ pg2_table = ets:new(pg2_table, [ordered_set, protected, named_table]),
+ {ok, #state{}}.
+
+-type call() :: {'create', name()}
+ | {'delete', name()}
+ | {'join', name(), pid()}
+ | {'leave', name(), pid()}.
+
+-spec handle_call(call(), _, #state{}) ->
+ {'reply', 'ok', #state{}}.
+
+handle_call({create, Name}, _From, S) ->
+ assure_group(Name),
+ {reply, ok, S};
+handle_call({join, Name, Pid}, _From, S) ->
+ ets:member(pg2_table, {group, Name}) andalso join_group(Name, Pid),
+ {reply, ok, S};
+handle_call({leave, Name, Pid}, _From, S) ->
+ ets:member(pg2_table, {group, Name}) andalso leave_group(Name, Pid),
+ {reply, ok, S};
+handle_call({delete, Name}, _From, S) ->
+ delete_group(Name),
+ {reply, ok, S};
+handle_call(Request, From, S) ->
+ error_logger:warning_msg("The pg2 server received an unexpected message:\n"
+ "handle_call(~p, ~p, _)\n",
+ [Request, From]),
+ {noreply, S}.
+
+-type all_members() :: [[name(),...]].
+-type cast() :: {'exchange', node(), all_members()}
+ | {'del_member', name(), pid()}.
+
+-spec handle_cast(cast(), #state{}) -> {'noreply', #state{}}.
+
+handle_cast({exchange, _Node, List}, S) ->
+ store(List),
+ {noreply, S};
+handle_cast(_, S) ->
+ %% Ignore {del_member, Name, Pid}.
+ {noreply, S}.
+
+-spec handle_info(tuple(), #state{}) -> {'noreply', #state{}}.
+
+handle_info({'DOWN', MonitorRef, process, _Pid, _Info}, S) ->
+ member_died(MonitorRef),
+ {noreply, S};
+handle_info({nodeup, Node}, S) ->
+ gen_server:cast({?MODULE, Node}, {exchange, node(), all_members()}),
+ {noreply, S};
+handle_info({new_pg2, Node}, S) ->
+ gen_server:cast({?MODULE, Node}, {exchange, node(), all_members()}),
+ {noreply, S};
+handle_info(_, S) ->
+ {noreply, S}.
+
+-spec terminate(term(), #state{}) -> 'ok'.
+
+terminate(_Reason, _S) ->
+ true = ets:delete(pg2_table),
+ ok.
+
+%%%
+%%% Local functions
+%%%
+
+%%% One ETS table, pg2_table, is used for bookkeeping. The type of the
+%%% table is ordered_set, and the fast matching of partially
+%%% instantiated keys is used extensively.
+%%%
+%%% {{group, Name}}
+%%% Process group Name.
+%%% {{ref, Pid}, RPid, MonitorRef, Counter}
+%%% {{ref, MonitorRef}, Pid}
+%%% Each process has one monitor. Sometimes a process is spawned to
+%%% monitor the pid (RPid). Counter is incremented when the Pid joins
+%%% some group.
+%%% {{member, Name, Pid}, GroupCounter}
+%%% {{local_member, Name, Pid}}
+%%% Pid is a member of group Name, GroupCounter is incremented when the
+%%% Pid joins the group Name.
+%%% {{pid, Pid, Name}}
+%%% Pid is a member of group Name.
+
+store(List) ->
+ _ = [(assure_group(Name)
+ andalso
+ [join_group(Name, P) || P <- Members -- group_members(Name)]) ||
+ [Name, Members] <- List],
+ ok.
+
+assure_group(Name) ->
+ Key = {group, Name},
+ ets:member(pg2_table, Key) orelse true =:= ets:insert(pg2_table, {Key}).
+
+delete_group(Name) ->
+ _ = [leave_group(Name, Pid) || Pid <- group_members(Name)],
+ true = ets:delete(pg2_table, {group, Name}),
+ ok.
+
+member_died(Ref) ->
+ [{{ref, Ref}, Pid}] = ets:lookup(pg2_table, {ref, Ref}),
+ Names = member_groups(Pid),
+ _ = [leave_group(Name, P) ||
+ Name <- Names,
+ P <- member_in_group(Pid, Name)],
+ %% Kept for backward compatibility with links. Can be removed, eventually.
+ _ = [gen_server:abcast(nodes(), ?MODULE, {del_member, Name, Pid}) ||
+ Name <- Names],
+ ok.
+
+join_group(Name, Pid) ->
+ Ref_Pid = {ref, Pid},
+ try _ = ets:update_counter(pg2_table, Ref_Pid, {4, +1})
+ catch _:_ ->
+ {RPid, Ref} = do_monitor(Pid),
+ true = ets:insert(pg2_table, {Ref_Pid, RPid, Ref, 1}),
+ true = ets:insert(pg2_table, {{ref, Ref}, Pid})
+ end,
+ Member_Name_Pid = {member, Name, Pid},
+ try _ = ets:update_counter(pg2_table, Member_Name_Pid, {2, +1})
+ catch _:_ ->
+ true = ets:insert(pg2_table, {Member_Name_Pid, 1}),
+ _ = [ets:insert(pg2_table, {{local_member, Name, Pid}}) ||
+ node(Pid) =:= node()],
+ true = ets:insert(pg2_table, {{pid, Pid, Name}})
+ end.
+
+leave_group(Name, Pid) ->
+ Member_Name_Pid = {member, Name, Pid},
+ try ets:update_counter(pg2_table, Member_Name_Pid, {2, -1}) of
+ N ->
+ if
+ N =:= 0 ->
+ true = ets:delete(pg2_table, {pid, Pid, Name}),
+ _ = [ets:delete(pg2_table, {local_member, Name, Pid}) ||
+ node(Pid) =:= node()],
+ true = ets:delete(pg2_table, Member_Name_Pid);
+ true ->
+ ok
+ end,
+ Ref_Pid = {ref, Pid},
+ case ets:update_counter(pg2_table, Ref_Pid, {4, -1}) of
+ 0 ->
+ [{Ref_Pid,RPid,Ref,0}] = ets:lookup(pg2_table, Ref_Pid),
+ true = ets:delete(pg2_table, {ref, Ref}),
+ true = ets:delete(pg2_table, Ref_Pid),
+ true = erlang:demonitor(Ref, [flush]),
+ kill_monitor_proc(RPid, Pid);
+ _ ->
+ ok
+ end
+ catch _:_ ->
+ ok
+ end.
+
+all_members() ->
+ [[G, group_members(G)] || G <- all_groups()].
+
+group_members(Name) ->
+ [P ||
+ [P, N] <- ets:match(pg2_table, {{member, Name, '$1'},'$2'}),
+ _ <- lists:seq(1, N)].
+
+local_group_members(Name) ->
+ [P ||
+ [Pid] <- ets:match(pg2_table, {{local_member, Name, '$1'}}),
+ P <- member_in_group(Pid, Name)].
+
+member_in_group(Pid, Name) ->
+ case ets:lookup(pg2_table, {member, Name, Pid}) of
+ [] -> [];
+ [{{member, Name, Pid}, N}] ->
+ lists:duplicate(N, Pid)
+ end.
+
+member_groups(Pid) ->
+ [Name || [Name] <- ets:match(pg2_table, {{pid, Pid, '$1'}})].
+
+all_groups() ->
+ [N || [N] <- ets:match(pg2_table, {{group,'$1'}})].
+
+ensure_started() ->
+ case whereis(?MODULE) of
+ undefined ->
+ C = {pg2, {?MODULE, start_link, []}, permanent,
+ 1000, worker, [?MODULE]},
+ supervisor:start_child(kernel_safe_sup, C);
+ Pg2Pid ->
+ {ok, Pg2Pid}
+ end.
+
+
+kill_monitor_proc(RPid, Pid) ->
+ RPid =:= Pid orelse exit(RPid, kill).
+
+%% When/if erlang:monitor() returns before trying to connect to the
+%% other node this function can be removed.
+do_monitor(Pid) ->
+ case (node(Pid) =:= node()) orelse lists:member(node(Pid), nodes()) of
+ true ->
+ %% Assume the node is still up
+ {Pid, erlang:monitor(process, Pid)};
+ false ->
+ F = fun() ->
+ Ref = erlang:monitor(process, Pid),
+ receive
+ {'DOWN', Ref, process, Pid, _Info} ->
+ exit(normal)
+ end
+ end,
+ erlang:spawn_monitor(F)
+ end.
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