nickva commented on code in PR #5602: URL: https://github.com/apache/couchdb/pull/5602#discussion_r2317665376
########## src/couch_srt/src/couch_srt_server.erl: ########## @@ -0,0 +1,318 @@ +% Licensed under the Apache License, Version 2.0 (the "License"); you may not +% use this file except in compliance with the License. You may obtain a copy of +% the License at +% +% http://www.apache.org/licenses/LICENSE-2.0 +% +% Unless required by applicable law or agreed to in writing, software +% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +% License for the specific language governing permissions and limitations under +% the License. + +-module(couch_srt_server). + +-behaviour(gen_server). + +-export([ + start_link/0, + init/1, + handle_call/3, + handle_cast/2 +]). + +-export([ + create_pid_ref/0, + create_resource/1, + destroy_resource/1, + get_resource/1, + get_context_type/1, + inc/2, + inc/3, + match_resource/1, + new_context/2, + set_context_dbname/2, + set_context_handler_fun/2, + set_context_type/2, + set_context_username/2, + update_counter/3, + update_counter/4, + update_counters/2, + update_counters/3 +]). + +-include_lib("stdlib/include/ms_transform.hrl"). +-include_lib("couch_srt.hrl"). + +-record(st, {}). + +%% +%% Public API +%% + +-spec create_pid_ref() -> pid_ref(). +create_pid_ref() -> + {self(), make_ref()}. + +%% +%% +%% Context lifecycle API +%% + +-spec new_context(Type :: rctx_type(), Nonce :: nonce()) -> rctx(). +new_context(Type, Nonce) -> + #rctx{ + nonce = Nonce, + pid_ref = create_pid_ref(), + type = Type + }. + +-spec set_context_dbname(DbName, PidRef) -> boolean() when + DbName :: dbname(), PidRef :: maybe_pid_ref(). +set_context_dbname(_, undefined) -> + false; +set_context_dbname(DbName, PidRef) -> + update_element(PidRef, [{#rctx.dbname, DbName}]). + +-spec set_context_handler_fun({Mod, Func}, PidRef) -> boolean() when + Mod :: atom(), Func :: atom(), PidRef :: maybe_pid_ref(). +set_context_handler_fun(_, undefined) -> + false; +set_context_handler_fun({Mod, Func}, PidRef) -> + case get_resource(PidRef) of + undefined -> + false; + #rctx{} = Rctx -> + %% TODO: #coordinator{} assumption needs to adapt for other types + case couch_srt_server:get_context_type(Rctx) of + #coordinator{} = Coordinator0 -> + Coordinator = Coordinator0#coordinator{mod = Mod, func = Func}, + set_context_type(Coordinator, PidRef); + _ -> + false + end + end. + +-spec set_context_username(UserName, PidRef) -> boolean() when + UserName :: username(), PidRef :: maybe_pid_ref(). +set_context_username(_, undefined) -> + false; +set_context_username(UserName, PidRef) -> + update_element(PidRef, [{#rctx.username, UserName}]). + +-spec get_context_type(Rctx :: rctx()) -> rctx_type(). +get_context_type(#rctx{type = Type}) -> + Type. + +-spec set_context_type(Type, PidRef) -> boolean() when + Type :: rctx_type(), PidRef :: maybe_pid_ref(). +set_context_type(Type, PidRef) -> + update_element(PidRef, [{#rctx.type, Type}]). + +-spec create_resource(Rctx :: rctx()) -> boolean(). +create_resource(#rctx{} = Rctx) -> + (catch ets:insert(?CSRT_ETS, Rctx)) == true. + +-spec destroy_resource(PidRef :: maybe_pid_ref()) -> boolean(). +destroy_resource(undefined) -> + false; +destroy_resource({_, _} = PidRef) -> + (catch ets:delete(?CSRT_ETS, PidRef)) == true. + +-spec get_resource(PidRef :: maybe_pid_ref()) -> maybe_rctx(). +get_resource(undefined) -> + undefined; +get_resource(PidRef) -> + try ets:lookup(?CSRT_ETS, PidRef) of + [#rctx{} = Rctx] -> + Rctx; + [] -> + undefined + catch + _:_ -> + undefined + end. + +-spec match_resource(Rctx :: maybe_rctx()) -> [] | [rctx()]. +match_resource(undefined) -> + []; +match_resource(#rctx{} = Rctx) -> + try + ets:match_object(?CSRT_ETS, Rctx) + catch + _:_ -> + [] + end. + +%% Is this a valid #rctx{} field for inducing ets:update_counter upon? +-spec is_rctx_stat_field(Field :: rctx_field() | atom()) -> boolean(). +is_rctx_stat_field(Field) -> + maps:is_key(Field, ?STAT_KEYS_TO_FIELDS). + +%% Get the #rctx{} field record index of the corresponding stat counter field +-spec get_rctx_stat_field(Field :: rctx_field()) -> + non_neg_integer() + | throw({badkey, Key :: any()}). +get_rctx_stat_field(Field) -> + maps:get(Field, ?STAT_KEYS_TO_FIELDS). + +%% This provides a base set of updates to include along with any other #rctx{} +%% updates. Specifically, this provides a way to automatically track and +%% increment the #rctx.updated_at field without having to do ets:lookup to find +%% the last updated_at time, or having to do ets:update_element to set a +%% specific updated_at. We trade a pdict marker to keep inc operations as only +%% a singular ets call while sneaking in updated_at. +%% Calling couch_srt_util:put_updated_at/1 within this function is not the cleanest, +%% but it allows us to encapsulate the automatic updated_at inclusion into the +%% ?MODULE:update_counter(s)/3-4 arity call-through while still allowing the +%% 4-arity version to be exposed to pass an empty base updates list. Isolating +%% this logic means the final arity functions operate independently of any +%% local pdict values. +-spec make_base_counter_updates() -> counter_updates_list(). +make_base_counter_updates() -> + case couch_srt_util:get_updated_at() of + undefined -> + []; + LastUpdated -> + Now = couch_srt_util:tnow(), + couch_srt_util:put_updated_at(Now), + UpdatedInc = couch_srt_util:make_dt(LastUpdated, Now, native), + [{#rctx.updated_at, UpdatedInc}] + end. + +-spec update_counter(PidRef, Field, Count) -> non_neg_integer() when + PidRef :: maybe_pid_ref(), + Field :: rctx_field(), + Count :: non_neg_integer(). +update_counter(undefined, _Field, _Count) -> + 0; +update_counter(_PidRef, _Field, 0) -> + 0; +update_counter(PidRef, Field, Count) -> + %% Only call make_base_counter_updates() if PidRef, Field, Count all valid + case is_rctx_stat_field(Field) of + true -> + update_counter(PidRef, Field, Count, make_base_counter_updates()); + false -> + 0 + end. + +-spec update_counter(PidRef, Field, Count, BaseUpdates) -> non_neg_integer() when + PidRef :: maybe_pid_ref(), + Field :: rctx_field(), + Count :: non_neg_integer(), + BaseUpdates :: [] | [{rctx_field(), integer()}]. +update_counter(undefined, _Field, _Count, _BaseUpdates) -> + 0; +update_counter({_Pid, _Ref} = PidRef, Field, Count, BaseUpdates) when Count >= 0 -> + case is_rctx_stat_field(Field) of + true -> + Updates = [{get_rctx_stat_field(Field), Count} | BaseUpdates], + try + ets:update_counter(?CSRT_ETS, PidRef, Updates, #rctx{pid_ref = PidRef}) + catch + _:_ -> + 0 + end; + false -> + 0 + end. + +-spec update_counters(PidRef, Delta) -> boolean() when + PidRef :: maybe_pid_ref(), + Delta :: delta(). +update_counters(undefined, _Delta) -> + false; +update_counters(PidRef, Delta) when is_map(Delta) -> + update_counters(PidRef, Delta, make_base_counter_updates()). + +-spec update_counters(PidRef, Delta, BaseUpdates) -> boolean() when + PidRef :: maybe_pid_ref(), + Delta :: delta(), + BaseUpdates :: [] | [{rctx_field(), integer()}]. +update_counters(undefined, _Delta, _BaseUpdates) -> + false; +update_counters({_Pid, _Ref} = PidRef, Delta, BaseUpdates) when is_map(Delta) -> + Updates = maps:fold( + fun(Field, Count, Acc) -> + case is_rctx_stat_field(Field) of + true -> + [{get_rctx_stat_field(Field), Count} | Acc]; + false -> + %% This skips entries that are not is_rctx_stat_field's + %% Another approach would be: + %% lists:all(lists:map(fun is_rctx_stat_field/1, maps:keys(Delta))) + %% But that's a lot of looping for not even acumulating the update. + %% Need to drop Delta.dt either way as it's not an rctx_field + Acc + end + end, + BaseUpdates, + Delta + ), + + case Updates of + [] -> + false; + _ -> + try + ets:update_counter(?CSRT_ETS, PidRef, Updates, #rctx{pid_ref = PidRef}), + true + catch + _:_ -> + false + end + end. + +-spec inc(PidRef :: maybe_pid_ref(), Field :: rctx_field()) -> non_neg_integer(). +inc(PidRef, Field) -> + inc(PidRef, Field, 1). + +-spec inc(PidRef, Field, N) -> non_neg_integer() when + PidRef :: maybe_pid_ref(), + Field :: rctx_field(), + N :: non_neg_integer(). +inc(undefined, _Field, _) -> + 0; +inc(_PidRef, _Field, 0) -> + 0; +inc({_Pid, _Ref} = PidRef, Field, N) when is_integer(N) andalso N > 0 -> + case is_rctx_stat_field(Field) of + true -> + update_counter(PidRef, Field, N); + false -> + 0 + end. + +%% +%% gen_server callbacks +%% + +start_link() -> + gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). + +init([]) -> + ets:new(?CSRT_ETS, [ + named_table, + public, + {write_concurrency, auto}, + {read_concurrency, true}, + {keypos, #rctx.pid_ref} + ]), + {ok, #st{}}. + +handle_call(Msg, From, State) -> + {stop, {unknown_call, Msg, From}, State}. + +handle_cast(Msg, State) -> + {stop, {unknown_cast, Msg}, State}. + +%% +%% private functions +%% + +-spec update_element(PidRef :: maybe_pid_ref(), Updates :: [tuple()]) -> boolean(). +update_element(undefined, _Update) -> + false; +update_element({_Pid, _Ref} = PidRef, Update) -> + (catch ets:update_element(?CSRT_ETS, PidRef, Update)) == true. Review Comment: Catch `error:badarg` if we're protecting against a missing ets table. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: notifications-unsubscr...@couchdb.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
