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gproc.erl
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gproc.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.''
%%
%% @author Ulf Wiger <ulf.wiger@erlang-consulting.com>
%%
%% @doc Extended process registry
%% This module implements an extended process registry
%%
%% For a detailed description, see
%% <a href="erlang07-wiger.pdf">erlang07-wiger.pdf</a>.
%%
%% <h2>Tuning Gproc performance</h2>
%%
%% Gproc relies on a central server and an ordered-set ets table.
%% Effort is made to perform as much work as possible in the client without
%% sacrificing consistency. A few things can be tuned by setting the following
%% application environment variables in the top application of `gproc'
%% (usually `gproc'):
%%
%% * `{ets_options, list()}' - Currently, the options `{write_concurrency, F}'
%% and `{read_concurrency, F}' are allowed. The default is
%% `[{write_concurrency, true}, {read_concurrency, true}]'
%% * `{server_options, list()}' - These will be passed as spawn options when
%% starting the `gproc' and `gproc_dist' servers. Default is `[]'. It is
%% likely that `{priority, high | max}' and/or increasing `min_heap_size'
%% will improve performance.
%%
%% @end
%% @type type() = n | p | c | a. n = name; p = property; c = counter;
%% a = aggregate_counter
%% @type scope() = l | g. l = local registration; g = global registration
%%
%% @type reg_id() = {type(), scope(), any()}.
%% @type unique_id() = {n | a, scope(), any()}.
%%
%% @type sel_scope() = scope | all | global | local.
%% @type sel_type() = type() | names | props | counters | aggr_counters.
%% @type context() = {scope(), type()} | type(). {'all','all'} is the default
%%
%% @type headpat() = {keypat(),pidpat(),ValPat}.
%% @type keypat() = {sel_type() | sel_var(),
%% l | g | sel_var(),
%% any()}.
%% @type pidpat() = pid() | sel_var().
%% sel_var() = DollarVar | '_'.
%% @type sel_pattern() = [{headpat(), Guards, Prod}].
%% @type key() = {type(), scope(), any()}.
-module(gproc).
-behaviour(gen_server).
-export([start_link/0,
reg/1, reg/2, unreg/1,
reg_shared/1, reg_shared/2, unreg_shared/1,
mreg/3,
munreg/3,
set_value/2,
get_value/1, get_value/2,
where/1,
await/1, await/2,
nb_wait/1,
cancel_wait/2,
cancel_wait_or_monitor/1,
monitor/1,
demonitor/2,
lookup_pid/1,
lookup_pids/1,
lookup_value/1,
lookup_values/1,
update_counter/2,
reset_counter/1,
update_shared_counter/2,
give_away/2,
goodbye/0,
send/2,
info/1, info/2,
i/0,
select/1, select/2, select/3,
select_count/1, select_count/2,
first/1,
next/2,
prev/2,
last/1,
table/0, table/1, table/2]).
%% Environment handling
-export([get_env/3, get_env/4,
get_set_env/3, get_set_env/4,
set_env/5]).
%% Convenience functions
-export([add_local_name/1,
add_global_name/1,
add_local_property/2,
add_global_property/2,
add_local_counter/2,
add_global_counter/2,
add_local_aggr_counter/1,
add_global_aggr_counter/1,
add_shared_local_counter/2,
lookup_local_name/1,
lookup_global_name/1,
lookup_local_properties/1,
lookup_global_properties/1,
lookup_local_counters/1,
lookup_global_counters/1,
lookup_local_aggr_counter/1,
lookup_global_aggr_counter/1]).
%% Callbacks for behaviour support
-export([whereis_name/1,
register_name/2,
unregister_name/1]).
-export([default/1]).
%%% internal exports
-export([init/1,
handle_cast/2,
handle_call/3,
handle_info/2,
code_change/3,
terminate/2]).
%% this shouldn't be necessary
-export([audit_process/1]).
-include("gproc.hrl").
-include_lib("eunit/include/eunit.hrl").
-define(SERVER, ?MODULE).
%%-define(l, l(?LINE)). % when activated, calls a traceable empty function
-define(l, ignore).
-define(CHK_DIST,
case whereis(gproc_dist) of
undefined ->
erlang:error(local_only);
_ ->
ok
end).
-record(state, {}).
%% @spec () -> {ok, pid()}
%%
%% @doc Starts the gproc server.
%%
%% This function is intended to be called from gproc_sup, as part of
%% starting the gproc application.
%% @end
start_link() ->
_ = create_tabs(),
SpawnOpts = gproc_lib:valid_opts(server_options, []),
gen_server:start_link({local, ?SERVER}, ?MODULE, [],
[{spawn_opt, SpawnOpts}]).
%% spec(Name::any()) -> true
%%
%% @doc Registers a local (unique) name. @equiv reg({n,l,Name})
%% @end
%%
add_local_name(Name) -> reg({n,l,Name}, undefined).
%% spec(Name::any()) -> true
%%
%% @doc Registers a global (unique) name. @equiv reg({n,g,Name})
%% @end
%%
add_global_name(Name) -> reg({n,g,Name}, undefined).
%% spec(Name::any(), Value::any()) -> true
%%
%% @doc Registers a local (non-unique) property. @equiv reg({p,l,Name},Value)
%% @end
%%
add_local_property(Name , Value) -> reg({p,l,Name}, Value).
%% spec(Name::any(), Value::any()) -> true
%%
%% @doc Registers a global (non-unique) property. @equiv reg({p,g,Name},Value)
%% @end
%%
add_global_property(Name, Value) -> reg({p,g,Name}, Value).
%% spec(Name::any(), Initial::integer()) -> true
%%
%% @doc Registers a local (non-unique) counter. @equiv reg({c,l,Name},Value)
%% @end
%%
add_local_counter(Name, Initial) when is_integer(Initial) ->
reg({c,l,Name}, Initial).
%% spec(Name::any(), Initial::integer()) -> true
%%
%% @doc Registers a local shared (unique) counter.
%% @equiv reg_shared({c,l,Name},Value)
%% @end
%%
add_shared_local_counter(Name, Initial) when is_integer(Initial) ->
reg_shared({c,l,Name}, Initial).
%% spec(Name::any(), Initial::integer()) -> true
%%
%% @doc Registers a global (non-unique) counter. @equiv reg({c,g,Name},Value)
%% @end
%%
add_global_counter(Name, Initial) when is_integer(Initial) ->
reg({c,g,Name}, Initial).
%% spec(Name::any()) -> true
%%
%% @doc Registers a local (unique) aggregated counter.
%% @equiv reg({a,l,Name})
%% @end
%%
add_local_aggr_counter(Name) -> reg({a,l,Name}).
%% spec(Name::any()) -> true
%%
%% @doc Registers a global (unique) aggregated counter.
%% @equiv reg({a,g,Name})
%% @end
%%
add_global_aggr_counter(Name) -> reg({a,g,Name}).
%% @spec (Name::any()) -> pid()
%%
%% @doc Lookup a local unique name. Fails if there is no such name.
%% @equiv where({n,l,Name})
%% @end
%%
lookup_local_name(Name) -> where({n,l,Name}).
%% @spec (Name::any()) -> pid()
%%
%% @doc Lookup a global unique name. Fails if there is no such name.
%% @equiv where({n,g,Name})
%% @end
%%
lookup_global_name(Name) -> where({n,g,Name}).
%% @spec (Name::any()) -> integer()
%%
%% @doc Lookup a local (unique) aggregated counter and returns its value.
%% Fails if there is no such object.
%% @equiv where({a,l,Name})
%% @end
%%
lookup_local_aggr_counter(Name) -> lookup_value({a,l,Name}).
%% @spec (Name::any()) -> integer()
%%
%% @doc Lookup a global (unique) aggregated counter and returns its value.
%% Fails if there is no such object.
%% @equiv where({a,g,Name})
%% @end
%%
lookup_global_aggr_counter(Name) -> lookup_value({a,g,Name}).
%% @spec (Property::any()) -> [{pid(), Value}]
%%
%% @doc Look up all local (non-unique) instances of a given Property.
%% Returns a list of {Pid, Value} tuples for all matching objects.
%% @equiv lookup_values({p, l, Property})
%% @end
%%
lookup_local_properties(P) -> lookup_values({p,l,P}).
%% @spec (Property::any()) -> [{pid(), Value}]
%%
%% @doc Look up all global (non-unique) instances of a given Property.
%% Returns a list of {Pid, Value} tuples for all matching objects.
%% @equiv lookup_values({p, g, Property})
%% @end
%%
lookup_global_properties(P) -> lookup_values({p,g,P}).
%% @spec (Counter::any()) -> [{pid(), Value::integer()}]
%%
%% @doc Look up all local (non-unique) instances of a given Counter.
%% Returns a list of {Pid, Value} tuples for all matching objects.
%% @equiv lookup_values({c, l, Counter})
%% @end
%%
lookup_local_counters(P) -> lookup_values({c,l,P}).
%% @spec (Counter::any()) -> [{pid(), Value::integer()}]
%%
%% @doc Look up all global (non-unique) instances of a given Counter.
%% Returns a list of {Pid, Value} tuples for all matching objects.
%% @equiv lookup_values({c, g, Counter})
%% @end
%%
lookup_global_counters(P) -> lookup_values({c,g,P}).
%% @spec get_env(Scope::scope(), App::atom(), Key::atom()) -> term()
%% @equiv get_env(Scope, App, Key, [app_env])
get_env(Scope, App, Key) ->
get_env(Scope, App, Key, [app_env]).
%% @spec (Scope::scope(), App::atom(), Key::atom(), Strategy) -> term()
%% Strategy = [Alternative]
%% Alternative = app_env
%% | os_env
%% | inherit | {inherit, pid()} | {inherit, unique_id()}
%% | init_arg
%% | {mnesia, ActivityType, Oid, Pos}
%% | {default, term()}
%% | error
%% @doc Read an environment value, potentially cached as a `gproc_env' property.
%%
%% This function first tries to read the value of a cached property,
%% `{p, Scope, {gproc_env, App, Key}}'. If this fails, it will try the provided
%% alternative strategy. `Strategy' is a list of alternatives, tried in order.
%% Each alternative can be one of:
%%
%% * `app_env' - try `application:get_env(App, Key)'
%% * `os_env' - try `os:getenv(ENV)', where `ENV' is `Key' converted into an
%% uppercase string
%% * `{os_env, ENV}' - try `os:getenv(ENV)'
%% * `inherit' - inherit the cached value, if any, held by the parent process.
%% * `{inherit, Pid}' - inherit the cached value, if any, held by `Pid'.
%% * `{inherit, Id}' - inherit the cached value, if any, held by the process
%% registered in `gproc' as `Id'.
%% * `init_arg' - try `init:get_argument(Key)'; expects a single value, if any.
%% * `{mnesia, ActivityType, Oid, Pos}' - try
%% `mnesia:activity(ActivityType, fun() -> mnesia:read(Oid) end)'; retrieve
%% the value in position `Pos' if object found.
%% * `{default, Value}' - set a default value to return once alternatives have
%% been exhausted; if not set, `undefined' will be returned.
%% * `error' - raise an exception, `erlang:error(gproc_env, [App, Key, Scope])'.
%%
%% While any alternative can occur more than once, the only one that might make
%% sense to use multiple times is `{default, Value}'.
%%
%% The return value will be one of:
%%
%% * The value of the first matching alternative, or `error' eception,
%% whichever comes first
%% * The last instance of `{default, Value}', or `undefined', if there is no
%% matching alternative, default or `error' entry in the list.
%%
%% The `error' option can be used to assert that a value has been previously
%% cached. Alternatively, it can be used to assert that a value is either cached
%% or at least defined somewhere,
%% e.g. `get_env(l, mnesia, dir, [app_env, error])'.
%% @end
get_env(Scope, App, Key, Strategy)
when Scope==l, is_atom(App), is_atom(Key);
Scope==g, is_atom(App), is_atom(Key) ->
do_get_env(Scope, App, Key, Strategy, false).
%% @spec get_set_env(Scope::scope(), App::atom(), Key::atom()) -> term()
%% @equiv get_set_env(Scope, App, Key, [app_env])
get_set_env(Scope, App, Key) ->
get_set_env(Scope, App, Key, [app_env]).
%% @spec get_set_env(Scope::scope(), App::atom(), Key::atom(), Strategy) ->
%% Value
%% @doc Fetch and cache an environment value, if not already cached.
%%
%% This function does the same thing as {@link get_env/4}, but also updates the
%% cache. Note that the cache will be updated even if the result of the lookup
%% is `undefined'.
%%
%% @see get_env/4.
%% @end
%%
get_set_env(Scope, App, Key, Strategy)
when Scope==l, is_atom(App), is_atom(Key);
Scope==g, is_atom(App), is_atom(Key) ->
do_get_env(Scope, App, Key, Strategy, true).
do_get_env(Context, App, Key, Alternatives, Set) ->
case lookup_env(Context, App, Key, self()) of
undefined ->
check_alternatives(Alternatives, Context, App, Key, undefined, Set);
{ok, Value} ->
Value
end.
%% @spec set_env(Scope::scope(), App::atom(),
%% Key::atom(), Value::term(), Strategy) -> Value
%% Strategy = [Alternative]
%% Alternative = app_env | os_env | {os_env, VAR}
%% | {mnesia, ActivityType, Oid, Pos}
%%
%% @doc Updates the cached value as well as underlying environment.
%%
%% This function should be exercised with caution, as it affects the larger
%% environment outside gproc. This function modifies the cached value, and then
%% proceeds to update the underlying environment (OS environment variable or
%% application environment variable).
%%
%% When the `mnesia' alternative is used, gproc will try to update any existing
%% object, changing only the `Pos' position. If no such object exists, it will
%% create a new object, setting any other attributes (except `Pos' and the key)
%% to `undefined'.
%% @end
%%
set_env(Scope, App, Key, Value, Strategy)
when Scope==l, is_atom(App), is_atom(Key);
Scope==g, is_atom(App), is_atom(Key) ->
case is_valid_set_strategy(Strategy, Value) of
true ->
update_cached_env(Scope, App, Key, Value),
set_strategy(Strategy, App, Key, Value);
false ->
erlang:error(badarg)
end.
check_alternatives([{default, Val}|Alts], Scope, App, Key, _, Set) ->
check_alternatives(Alts, Scope, App, Key, Val, Set);
check_alternatives([H|T], Scope, App, Key, Def, Set) ->
case try_alternative(H, App, Key, Scope) of
undefined ->
check_alternatives(T, Scope, App, Key, Def, Set);
{ok, Value} ->
if Set ->
cache_env(Scope, App, Key, Value),
Value;
true ->
Value
end
end;
check_alternatives([], Scope, App, Key, Def, Set) ->
if Set ->
cache_env(Scope, App, Key, Def);
true ->
ok
end,
Def.
try_alternative(error, App, Key, Scope) ->
erlang:error(gproc_env, [App, Key, Scope]);
try_alternative(inherit, App, Key, Scope) ->
case get('$ancestors') of
[P|_] ->
lookup_env(Scope, App, Key, P);
_ ->
undefined
end;
try_alternative({inherit, P}, App, Key, Scope) when is_pid(P) ->
lookup_env(Scope, App, Key, P);
try_alternative({inherit, P}, App, Key, Scope) ->
case where(P) of
undefined -> undefined;
Pid when is_pid(Pid) ->
lookup_env(Scope, App, Key, Pid)
end;
try_alternative(app_env, App, Key, _Scope) ->
case application:get_env(App, Key) of
undefined -> undefined;
{ok, undefined} -> undefined;
{ok, Value} -> {ok, Value}
end;
try_alternative(os_env, _App, Key, _) ->
case os:getenv(os_env_key(Key)) of
false -> undefined;
Val -> {ok, Val}
end;
try_alternative({os_env, Key}, _, _, _) ->
case os:getenv(Key) of
false -> undefined;
Val -> {ok, Val}
end;
try_alternative(init_arg, _, Key, _) ->
case init:get_argument(Key) of
{ok, [[Value]]} ->
{ok, Value};
error ->
undefined
end;
try_alternative({mnesia,Type,Key,Pos}, _, _, _) ->
case mnesia:activity(Type, fun() -> mnesia:read(Key) end) of
[] -> undefined;
[Found] ->
{ok, element(Pos, Found)}
end.
os_env_key(Key) ->
string:to_upper(atom_to_list(Key)).
lookup_env(Scope, App, Key, P) ->
case ets:lookup(?TAB, {{p, Scope, {gproc_env, App, Key}}, P}) of
[] ->
undefined;
[{_, _, Value}] ->
{ok, Value}
end.
cache_env(Scope, App, Key, Value) ->
reg({p, Scope, {gproc_env, App, Key}}, Value).
update_cached_env(Scope, App, Key, Value) ->
case lookup_env(Scope, App, Key, self()) of
undefined ->
cache_env(Scope, App, Key, Value);
{ok, _} ->
set_value({p, Scope, {gproc_env, App, Key}}, Value)
end.
is_valid_set_strategy([os_env|T], Value) ->
is_string(Value) andalso is_valid_set_strategy(T, Value);
is_valid_set_strategy([{os_env, _}|T], Value) ->
is_string(Value) andalso is_valid_set_strategy(T, Value);
is_valid_set_strategy([app_env|T], Value) ->
is_valid_set_strategy(T, Value);
is_valid_set_strategy([{mnesia,_Type,_Oid,_Pos}|T], Value) ->
is_valid_set_strategy(T, Value);
is_valid_set_strategy([], _) ->
true;
is_valid_set_strategy(_, _) ->
false.
set_strategy([H|T], App, Key, Value) ->
case H of
app_env ->
application:set_env(App, Key, Value);
os_env ->
os:putenv(os_env_key(Key), Value);
{os_env, ENV} ->
os:putenv(ENV, Value);
{mnesia,Type,Oid,Pos} ->
mnesia:activity(
Type,
fun() ->
Rec = case mnesia:read(Oid) of
[] ->
{Tab,K} = Oid,
Tag = mnesia:table_info(Tab, record_name),
Attrs = mnesia:table_info(Tab, attributes),
list_to_tuple(
[Tag,K |
[undefined || _ <- tl(Attrs)]]);
[Old] ->
Old
end,
mnesia:write(setelement(Pos, Rec, Value))
end)
end,
set_strategy(T, App, Key, Value);
set_strategy([], _, _, Value) ->
Value.
is_string(S) ->
try begin _ = iolist_to_binary(S),
true
end
catch
error:_ ->
false
end.
%% @spec reg(Key::key()) -> true
%%
%% @doc
%% @equiv reg(Key, default(Key))
%% @end
reg(Key) ->
reg(Key, default(Key)).
default({T,_,_}) when T==c -> 0;
default(_) -> undefined.
%% @spec await(Key::key()) -> {pid(),Value}
%% @equiv await(Key,infinity)
%%
await(Key) ->
await(Key, infinity).
%% @spec await(Key::key(), Timeout) -> {pid(),Value}
%% Timeout = integer() | infinity
%%
%% @doc Wait for a local name to be registered.
%% The function raises an exception if the timeout expires. Timeout must be
%% either an interger > 0 or 'infinity'.
%% A small optimization: we first perform a lookup, to see if the name
%% is already registered. This way, the cost of the operation will be
%% roughly the same as of where/1 in the case where the name is already
%% registered (the difference: await/2 also returns the value).
%% @end
%%
await({n,g,_} = Key, Timeout) ->
?CHK_DIST,
request_wait(Key, Timeout);
await({n,l,_} = Key, Timeout) ->
case ets:lookup(?TAB, {Key, n}) of
[{_, Pid, Value}] ->
{Pid, Value};
_ ->
request_wait(Key, Timeout)
end;
await(K, T) ->
erlang:error(badarg, [K, T]).
request_wait({n,C,_} = Key, Timeout) when C==l; C==g ->
TRef = case Timeout of
infinity -> no_timer;
T when is_integer(T), T > 0 ->
erlang:start_timer(T, self(), gproc_timeout);
_ ->
erlang:error(badarg, [Key, Timeout])
end,
WRef = case {call({await,Key,self()}, C), C} of
{{R, {Kg,Pg,Vg}}, g} ->
self() ! {gproc, R, registered, {Kg,Pg,Vg}},
R;
{R,_} ->
R
end,
receive
{gproc, WRef, registered, {_K, Pid, V}} ->
_ = case TRef of
no_timer -> ignore;
_ -> erlang:cancel_timer(TRef)
end,
{Pid, V};
{timeout, TRef, gproc_timeout} ->
cancel_wait(Key, WRef),
erlang:error(timeout, [Key, Timeout])
end.
%% @spec nb_wait(Key::key()) -> Ref
%%
%% @doc Wait for a local name to be registered.
%% The caller can expect to receive a message,
%% {gproc, Ref, registered, {Key, Pid, Value}}, once the name is registered.
%% @end
%%
nb_wait({n,g,_} = Key) ->
?CHK_DIST,
call({await, Key, self()}, g);
nb_wait({n,l,_} = Key) ->
call({await, Key, self()}, l);
nb_wait(Key) ->
erlang:error(badarg, [Key]).
%% @spec cancel_wait(Key::key(), Ref) -> ok
%% Ref = all | reference()
%%
%% @doc Cancels a previous call to nb_wait/1
%%
%% If `Ref = all', all wait requests on `Key' from the calling process
%% are canceled.
%% @end
%%
cancel_wait({_,g,_} = Key, Ref) ->
?CHK_DIST,
cast({cancel_wait, self(), Key, Ref}, g),
ok;
cancel_wait({_,l,_} = Key, Ref) ->
cast({cancel_wait, self(), Key, Ref}, l),
ok.
cancel_wait_or_monitor({_,g,_} = Key) ->
?CHK_DIST,
cast({cancel_wait_or_monitor, self(), Key}, g),
ok;
cancel_wait_or_monitor({_,l,_} = Key) ->
cast({cancel_wait_or_monitor, self(), Key}, l),
ok.
%% @spec monitor(key()) -> reference()
%%
%% @doc monitor a registered name
%% This function works much like erlang:monitor(process, Pid), but monitors
%% a unique name registered via gproc. A message, `{gproc, unreg, Ref, Key}'
%% will be sent to the requesting process, if the name is unregistered or
%% the registered process dies.
%%
%% If the name is not yet registered, the same message is sent immediately.
%% @end
monitor({T,g,_} = Key) when T==n; T==a ->
?CHK_DIST,
call({monitor, Key, self()}, g);
monitor({T,l,_} = Key) when T==n; T==a ->
call({monitor, Key, self()}, l);
monitor(Key) ->
erlang:error(badarg, [Key]).
%% @spec demonitor(key(), reference()) -> ok
%%
%% @doc Remove a monitor on a registered name
%% This function is the reverse of monitor/1. It removes a monitor previously
%% set on a unique name. This function always succeeds given legal input.
%% @end
demonitor({T,g,_} = Key, Ref) when T==n; T==a ->
?CHK_DIST,
call({demonitor, Key, Ref, self()}, g);
demonitor({T,l,_} = Key, Ref) when T==n; T==a ->
call({demonitor, Key, Ref, self()}, l);
demonitor(Key, Ref) ->
erlang:error(badarg, [Key, Ref]).
%% @spec reg(Key::key(), Value) -> true
%%
%% @doc Register a name or property for the current process
%%
%%
reg({_,g,_} = Key, Value) ->
%% anything global
?CHK_DIST,
gproc_dist:reg(Key, Value);
reg({p,l,_} = Key, Value) ->
local_reg(Key, Value);
reg({a,l,_} = Key, undefined) ->
call({reg, Key, undefined});
reg({c,l,_} = Key, Value) when is_integer(Value) ->
call({reg, Key, Value});
reg({n,l,_} = Key, Value) ->
call({reg, Key, Value});
reg(_, _) ->
erlang:error(badarg).
%% @spec reg_shared(Key::key()) -> true
%%
%% @doc Register a resource, but don't tie it to a particular process.
%%
%% `reg_shared({c,l,C}) -> reg_shared({c,l,C}, 0).'
%% `reg_shared({a,l,A}) -> reg_shared({a,l,A}, undefined).'
%% @end
reg_shared({c,_,_} = Key) ->
reg_shared(Key, 0);
reg_shared({a,_,_} = Key) ->
reg_shared(Key, undefined).
%% @spec reg_shared(Key::key(), Value) -> true
%%
%% @doc Register a resource, but don't tie it to a particular process.
%%
%% Shared resources are all unique. They remain until explicitly unregistered
%% (using {@link unreg_shared/1}). The types of shared resources currently
%% supported are `counter' and `aggregated counter'. In listings and query
%% results, shared resources appear as other similar resources, except that
%% `Pid == shared'. To wit, update_counter({c,l,myCounter}, 1, shared) would
%% increment the shared counter `myCounter' with 1, provided it exists.
%%
%% A shared aggregated counter will track updates in exactly the same way as
%% an aggregated counter which is owned by a process.
%% @end
%%
reg_shared({_,g,_} = Key, Value) ->
%% anything global
?CHK_DIST,
gproc_dist:reg_shared(Key, Value);
reg_shared({a,l,_} = Key, undefined) ->
call({reg_shared, Key, undefined});
reg_shared({c,l,_} = Key, Value) when is_integer(Value) ->
call({reg_shared, Key, Value});
reg_shared(_, _) ->
erlang:error(badarg).
%% @spec mreg(type(), scope(), [{Key::any(), Value::any()}]) -> true
%%
%% @doc Register multiple {Key,Value} pairs of a given type and scope.
%%
%% This function is more efficient than calling {@link reg/2} repeatedly.
%% It is also atomic in regard to unique names; either all names are registered
%% or none are.
%% @end
mreg(T, g, KVL) ->
?CHK_DIST,
gproc_dist:mreg(T, KVL);
mreg(T, l, KVL) when T==a; T==n ->
if is_list(KVL) ->
call({mreg, T, l, KVL});
true ->
erlang:error(badarg)
end;
mreg(p, l, KVL) ->
local_mreg(p, KVL);
mreg(_, _, _) ->
erlang:error(badarg).
%% @spec munreg(type(), scope(), [Key::any()]) -> true
%%
%% @doc Unregister multiple Key items of a given type and scope.
%%
%% This function is usually more efficient than calling {@link unreg/1}
%% repeatedly.
%% @end
munreg(T, g, L) ->
?CHK_DIST,
gproc_dist:munreg(T, existing(T,g,L));
munreg(T, l, L) when T==a; T==n ->
if is_list(L) ->
call({munreg, T, l, existing(T,l,L)});
true ->
erlang:error(badarg)
end;
munreg(p, l, L) ->
local_munreg(p, existing(p,l,L));
munreg(_, _, _) ->
erlang:error(badarg).
existing(T,Scope,L) ->
Keys = if T==p; T==c ->
[{{T,Scope,K}, self()} || K <- L];
T==a; T==n ->
[{{T,Scope,K}, T} || K <- L]
end,
_ = [case ets:member(?TAB, K) of
false -> erlang:error(badarg);
true -> true
end || K <- Keys],
L.
%% @spec (Key:: key()) -> true
%%
%% @doc Unregister a name or property.
%% @end
unreg(Key) ->
case Key of
{_, g, _} ->
?CHK_DIST,
gproc_dist:unreg(Key);
{T, l, _} when T == n;
T == a -> call({unreg, Key});
{_, l, _} ->
case ets:member(?TAB, {Key,self()}) of
true ->
_ = gproc_lib:remove_reg(Key, self(), unreg),
true;
false ->
erlang:error(badarg)
end
end.
%% @spec (Key:: key()) -> true
%%
%% @doc Unregister a shared resource.
%% @end
unreg_shared(Key) ->
case Key of
{_, g, _} ->
?CHK_DIST,
gproc_dist:unreg_shared(Key);
{T, l, _} when T == c;
T == a -> call({unreg_shared, Key});
_ ->
erlang:error(badarg)
end.
%% @spec (key(), pid()) -> yes | no
%%
%% @doc Behaviour support callback
%% @end
register_name({n,_,_} = Name, Pid) when Pid == self() ->
try reg(Name), yes
catch
error:_ ->
no
end.
%% @equiv unreg/1
unregister_name(Key) ->
unreg(Key).
%% @spec (Continuation ::term()) -> {[Match],Continuation} | '$end_of_table'
%% @doc
%% see http://www.erlang.org/doc/man/ets.html#select-1
%% @end
select({?TAB, _, _, _, _, _, _, _} = Continuation) ->
ets:select(Continuation);
%% @spec (select_pattern()) -> list(sel_object())
%% @doc
%% @equiv select(all, Pat)
%% @end
select(Pat) ->
select(all, Pat).
%% @spec (Context::context(), Pat::sel_pattern()) -> [{Key, Pid, Value}]
%%
%% @doc Perform a select operation on the process registry.
%%
%% The physical representation in the registry may differ from the above,
%% but the select patterns are transformed appropriately.
%% @end
select(Context, Pat) ->
ets:select(?TAB, pattern(Pat, Context)).
%% @spec (Context::context(), Pat::sel_patten(), Limit::integer()) ->
%% {[Match],Continuation} | '$end_of_table'
%% @doc Like {@link select/2} but returns Limit objects at a time.
%%
%% See [http://www.erlang.org/doc/man/ets.html#select-3].
%% @end
select(Context, Pat, Limit) ->
ets:select(?TAB, pattern(Pat, Context), Limit).
%% @spec (select_pattern()) -> list(sel_object())
%% @doc
%% @equiv select_count(all, Pat)
%% @end
select_count(Pat) ->
select_count(all, Pat).
%% @spec (Context::context(), Pat::sel_pattern()) -> [{Key, Pid, Value}]
%%
%% @doc Perform a select_count operation on the process registry.
%%
%% The physical representation in the registry may differ from the above,
%% but the select patterns are transformed appropriately.
%% @end
select_count(Context, Pat) ->
ets: select_count(?TAB, pattern(Pat, Context)).
%%% Local properties can be registered in the local process, since
%%% no other process can interfere.
%%%
local_reg(Key, Value) ->
case gproc_lib:insert_reg(Key, Value, self(), l) of
false -> erlang:error(badarg);
true -> monitor_me()
end.
local_mreg(_, []) -> true;
local_mreg(T, [_|_] = KVL) ->
case gproc_lib:insert_many(T, l, KVL, self()) of
false -> erlang:error(badarg);
{true,_} -> monitor_me()
end.
local_munreg(T, L) when T==p; T==c ->
_ = [gproc_lib:remove_reg({T,l,K}, self(), unreg) || K <- L],
true.
%% @spec (Key :: key(), Value) -> true
%% @doc Sets the value of the registeration entry given by Key
%%
%% Key is assumed to exist and belong to the calling process.
%% If it doesn't, this function will exit.
%%
%% Value can be any term, unless the object is a counter, in which case
%% it must be an integer.
%% @end
%%
set_value({_,g,_} = Key, Value) ->
?CHK_DIST,
gproc_dist:set_value(Key, Value);
set_value({a,l,_} = Key, Value) when is_integer(Value) ->
call({set, Key, Value});
set_value({n,l,_} = Key, Value) ->
%% we cannot do this locally, since we have to check that the object
%% exists first - not an atomic update.
call({set, Key, Value});
set_value({p,l,_} = Key, Value) ->
%% we _can_ to this locally, since there is no race condition - no
%% other process can update our properties.
case gproc_lib:do_set_value(Key, Value, self()) of
true -> true;
false ->
erlang:error(badarg)
end;
set_value({c,l,_} = Key, Value) when is_integer(Value) ->
gproc_lib:do_set_counter_value(Key, Value, self());
set_value(_, _) ->
erlang:error(badarg).
%% @spec (Key) -> Value
%% @doc Reads the value stored with a key registered to the current process.
%%
%% If no such key is registered to the current process, this function exits.
%% @end
get_value(Key) ->
get_value(Key, self()).
%% @spec (Key, Pid) -> Value