nickva commented on code in PR #5602: URL: https://github.com/apache/couchdb/pull/5602#discussion_r2226795070
########## src/couch_srt/src/couch_srt.erl: ########## @@ -0,0 +1,952 @@ +% 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). + +-include_lib("couch/include/couch_db.hrl"). +-include_lib("couch_srt.hrl"). + +%% PidRef API +-export([ + destroy_pid_ref/0, + destroy_pid_ref/1, + create_pid_ref/0, + get_pid_ref/0, + get_pid_ref/1, + set_pid_ref/1 +]). + +%% Context Lifecycle API +-export([ + create_context/2, + create_coordinator_context/2, + create_worker_context/3, + destroy_context/0, + destroy_context/1, + get_resource/0, + get_resource/1, + set_context_dbname/1, + set_context_dbname/2, + set_context_handler_fun/1, + set_context_handler_fun/2, + set_context_username/1, + set_context_username/2 +]). + +%% Public API +-export([ + maybe_track_rexi_init_p/1, + maybe_track_local_counter/2, + clear_pdict_markers/0, + do_report/2, + is_enabled/0, + is_enabled_init_p/0, + is_enabled_reporting/0, + is_enabled_rpc_reporting/0, + maybe_report/2, + to_json/1 +]). + +%% Stats Collection API +-export([ + accumulate_delta/1, + add_delta/2, + docs_written/1, + extract_delta/1, + get_delta/0, + inc/1, + inc/2, + ioq_called/0, + js_filtered/1, + make_delta/0, + rctx_delta/2, + maybe_add_delta/1, + maybe_add_delta/2, + maybe_inc/2, + should_track_init_p/1 +]). + +%% RPC API +-export([ + rpc_run/1, + rpc_unsafe_run/1 +]). + +%% Aggregate Query API +-export([ + active/0, + active/1, + active_coordinators/0, + active_coordinators/1, + active_workers/0, + active_workers/1, + find_by_nonce/1, + find_by_pid/1, + find_by_pidref/1, + find_workers_by_pidref/1, + query_matcher/1, + query_matcher/2 +]). + +%% Recon API Ports of https://github.com/ferd/recon/releases/tag/2.5.6 +-export([ + pid_ref_attrs/1, + pid_ref_matchspec/1, + proc_window/3 +]). + +-export([ + query/1, + from/1, + group_by/1, + group_by/2, + sort_by/1, + sort_by/2, + count_by/1, + options/1, + unlimited/0, + with_limit/1, + + run/1, + unsafe_run/1 +]). + +-export_type([ + query/0, + query_expression/0, + query_option/0 +]). + +-opaque query() :: couch_srt_query:query(). +-opaque query_expression() :: couch_srt_query:query_expression(). +-opaque query_option() :: couch_srt_query:query_option(). + +%% +%% RPC Operations +%% + +-spec rpc_run(Query :: query()) -> + [ + #{ + node => node(), + result => [{aggregation_key(), pos_integer()}], + errors => [atom()] + } + ]. +rpc_run(Query) -> + Nodes = mem3:nodes(), + merge_results(Nodes, erpc:multicall(Nodes, ?MODULE, run, [Query])). + +-spec rpc_unsafe_run(Query :: query()) -> + [ + #{ + node => node(), + result => [{aggregation_key(), pos_integer()}], + errors => [atom()] + } + ]. +rpc_unsafe_run(Query) -> + Nodes = mem3:nodes(), + merge_results(Nodes, erpc:multicall(Nodes, ?MODULE, unsafe_run, [Query])). + +merge_results(Nodes, Resp) -> + %% The result of erpc:multicall is returned as a list where the result from each + %% node is placed at the same position as the node name is placed in Nodes. + %% That is why we can use `lists:zip/2` here. + lists:map(fun format_response/1, lists:zip(Nodes, Resp)). + +format_response({Node, {ok, {ok, Result}}}) -> + #{ + node => Node, + result => Result, + errors => [] + }; +format_response({Node, {ok, {error, Reason}}}) -> + #{ + node => Node, + result => none, + errors => [Reason] + }; +format_response({Node, {ok, Result}}) -> + #{ + node => Node, + result => Result, + errors => [] + }; +format_response({Node, {error, {erpc, Reason}}}) -> + #{ + node => Node, + result => none, + errors => [Reason] + }; +format_response({Node, {Tag, _}}) -> + #{ + node => Node, + result => none, + errors => [Tag] + }. + +%% +%% PidRef Operations +%% + +-spec get_pid_ref() -> maybe_pid_ref(). +get_pid_ref() -> + couch_srt_util:get_pid_ref(). + +-spec get_pid_ref(Rctx :: rctx()) -> pid_ref(). +get_pid_ref(Rctx) -> + couch_srt_util:get_pid_ref(Rctx). + +-spec set_pid_ref(PidRef :: pid_ref()) -> pid_ref(). +set_pid_ref(PidRef) -> + couch_srt_util:set_pid_ref(PidRef). + +-spec create_pid_ref() -> pid_ref(). +create_pid_ref() -> + couch_srt_server:create_pid_ref(). + +-spec destroy_pid_ref() -> maybe_pid_ref(). +destroy_pid_ref() -> + destroy_pid_ref(get_pid_ref()). + +%%destroy_pid_ref(undefined) -> +%% undefined; +-spec destroy_pid_ref(PidRef :: maybe_pid_ref()) -> maybe_pid_ref(). +destroy_pid_ref(_PidRef) -> + erase(?PID_REF). + +%% +%% Context Lifecycle API +%% + +-spec create_worker_context(From, MFA, Nonce) -> pid_ref() | false when + From :: pid_ref(), MFA :: mfa(), Nonce :: nonce(). +create_worker_context(From, {M, F, _A}, Nonce) -> + case is_enabled() of + true -> + Type = #rpc_worker{from = From, mod = M, func = F}, + create_context(Type, Nonce); + false -> + false + end. + +-spec create_coordinator_context(Httpd, Path) -> pid_ref() | false when + Httpd :: #httpd{}, Path :: list(). +create_coordinator_context(#httpd{method = Verb, nonce = Nonce}, Path0) -> + case is_enabled() of + true -> + Path = list_to_binary([$/ | Path0]), + Type = #coordinator{method = Verb, path = Path}, + create_context(Type, Nonce); + false -> + false + end. + +-spec create_context(Type :: rctx_type(), Nonce :: term()) -> pid_ref() | false. +create_context(Type, Nonce) -> + Rctx = couch_srt_server:new_context(Type, Nonce), + PidRef = get_pid_ref(Rctx), + set_pid_ref(PidRef), + try + couch_srt_util:put_delta_a(Rctx), + couch_srt_util:put_updated_at(Rctx), + couch_srt_server:create_resource(Rctx), + couch_srt_logger:track(Rctx), + PidRef + catch + _:_ -> + couch_srt_server:destroy_resource(PidRef), + %% calling destroy_context(PidRef) clears the tracker too + destroy_context(PidRef), + false + end. + +-spec set_context_dbname(DbName :: binary()) -> boolean(). +set_context_dbname(DbName) -> + set_context_dbname(DbName, get_pid_ref()). + +-spec set_context_dbname(DbName, PidRef) -> boolean() when + DbName :: binary(), PidRef :: maybe_pid_ref(). +set_context_dbname(_, undefined) -> + false; +set_context_dbname(DbName, PidRef) -> + is_enabled() andalso couch_srt_server:set_context_dbname(DbName, PidRef). + +-spec set_context_handler_fun(Handler) -> boolean() when + Handler :: function() | {atom(), atom()}. +set_context_handler_fun(Handler) -> + set_context_handler_fun(Handler, get_pid_ref()). + +-spec set_context_handler_fun(Handler, PidRef) -> boolean() when + Handler :: function() | {atom(), atom()}, PidRef :: maybe_pid_ref(). +set_context_handler_fun(_, undefined) -> + false; +set_context_handler_fun(Fun, PidRef) when is_function(Fun) -> + case is_enabled() of + false -> + false; + true -> + FProps = erlang:fun_info(Fun), + Mod = proplists:get_value(module, FProps), + Func = proplists:get_value(name, FProps), + set_context_handler_fun({Mod, Func}, PidRef) + end; +set_context_handler_fun({Mod, Func}, PidRef) -> + case is_enabled() of + false -> + false; + true -> + couch_srt_server:set_context_handler_fun({Mod, Func}, PidRef) + end. + +%% @equiv set_context_username(User, get_pid_ref()) +set_context_username(User) -> + set_context_username(User, get_pid_ref()). + +-spec set_context_username(User, PidRef) -> boolean() when + User :: null | undefined | #httpd{} | #user_ctx{} | binary(), + PidRef :: maybe_pid_ref(). +set_context_username(null, _) -> + false; +set_context_username(_, undefined) -> + false; +set_context_username(#httpd{user_ctx = Ctx}, PidRef) -> + set_context_username(Ctx, PidRef); +set_context_username(#user_ctx{name = Name}, PidRef) -> + set_context_username(Name, PidRef); +set_context_username(UserName, PidRef) -> + is_enabled() andalso couch_srt_server:set_context_username(UserName, PidRef). + +-spec destroy_context() -> ok. +destroy_context() -> + destroy_context(get_pid_ref()). + +-spec destroy_context(PidRef :: maybe_pid_ref()) -> ok. +destroy_context(undefined) -> + ok; +destroy_context(PidRef) -> + %% Stopping the tracker clears the ets entry for PidRef on its way out + couch_srt_logger:stop_tracker(), + destroy_pid_ref(PidRef), + clear_pdict_markers(), + ok. + +-spec clear_pdict_markers() -> ok. +clear_pdict_markers() -> + ok = lists:foreach( + fun + ({{csrt, _} = K, _V}) -> + erlang:erase(K); + (_) -> + ok + end, + erlang:get() + ). + +%% +%% Public API +%% + +-spec maybe_track_rexi_init_p({M, F, A}) -> couch_stats:response() when + M :: atom(), F :: atom(), A :: non_neg_integer(). +maybe_track_rexi_init_p({M, F, _A}) -> + Metric = [M, F, spawned], + case couch_srt:should_track_init_p(Metric) of + true -> couch_stats:increment_counter(Metric); + false -> ok + end. + +%% Only potentially track positive increments to counters +-spec maybe_track_local_counter(any(), any()) -> ok. +maybe_track_local_counter(Name, Val) when is_integer(Val) andalso Val > 0 -> + couch_srt:maybe_inc(Name, Val), + ok; +maybe_track_local_counter(_, _) -> + ok. + +%% @equiv couch_srt_util:is_enabled(). +-spec is_enabled() -> boolean(). +is_enabled() -> + couch_srt_util:is_enabled(). + +%% @equiv couch_srt_util:is_enabled_reporting(). +-spec is_enabled_reporting() -> boolean(). +is_enabled_reporting() -> + couch_srt_util:is_enabled_reporting(). + +%% @equiv couch_srt_util:is_enabled_rpc_reporting(). +-spec is_enabled_rpc_reporting() -> boolean(). +is_enabled_rpc_reporting() -> + couch_srt_util:is_enabled_rpc_reporting(). + +%% @equiv couch_srt_util:is_enabled_init_p(). +-spec is_enabled_init_p() -> boolean(). +is_enabled_init_p() -> + couch_srt_util:is_enabled_init_p(). + +-spec get_resource() -> maybe_rctx(). +get_resource() -> + get_resource(get_pid_ref()). + +-spec get_resource(PidRef :: maybe_pid_ref()) -> maybe_rctx(). +get_resource(PidRef) -> + couch_srt_server:get_resource(PidRef). + +%% Log a CSRT report if any filters match +-spec maybe_report(ReportName :: string(), PidRef :: pid_ref()) -> ok. +maybe_report(ReportName, PidRef) -> + couch_srt_logger:maybe_report(ReportName, PidRef). + +%% Direct report logic skipping should log filters +-spec do_report(ReportName :: string(), PidRef :: pid_ref()) -> boolean(). +do_report(ReportName, PidRef) -> + couch_srt_logger:do_report(ReportName, get_resource(PidRef)). + +-spec to_json(Rctx :: maybe_rctx()) -> map() | null. +to_json(undefined) -> + null; +to_json(Rctx) -> + couch_srt_entry:to_json(Rctx). + +%% +%% Stat Collection API +%% + +-spec inc(Key :: rctx_field()) -> non_neg_integer(). +inc(Key) -> + case is_enabled() of + true -> + couch_srt_server:inc(get_pid_ref(), Key); + false -> + 0 + end. + +-spec inc(Key :: rctx_field(), N :: non_neg_integer()) -> non_neg_integer(). +inc(Key, N) when is_integer(N) andalso N >= 0 -> + case is_enabled() of + true -> + couch_srt_server:inc(get_pid_ref(), Key, N); + false -> + 0 + end. + +-spec maybe_inc(Stat :: atom(), Val :: non_neg_integer()) -> non_neg_integer(). +maybe_inc(Stat, Val) -> + case maps:is_key(Stat, ?STATS_TO_KEYS) of + true -> + inc(maps:get(Stat, ?STATS_TO_KEYS), Val); + false -> + 0 + end. + +-spec should_track_init_p(Stat :: [atom()]) -> boolean(). +%% "Example to extend CSRT" +%% should_track_init_p([fabric_rpc, foo, spawned]) -> +%% is_enabled_init_p(); +should_track_init_p([fabric_rpc, all_docs, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, changes, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, get_all_security, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, map_view, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, open_doc, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, open_shard, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, reduce_view, spawned]) -> + is_enabled_init_p(); +should_track_init_p([fabric_rpc, update_docs, spawned]) -> + is_enabled_init_p(); +should_track_init_p(_Metric) -> + false. + +-spec ioq_called() -> non_neg_integer(). +ioq_called() -> + inc(ioq_calls). + +%% we cannot yet use stats couchdb.query_server.*.ddoc_filter because those +%% are collected in a dedicated process. +%% TODO: funnel back stats from background worker processes to the RPC worker +js_filtered(N) -> + inc(js_filter), + inc(js_filtered_docs, N). + +docs_written(N) -> + inc(docs_written, N). + +-spec accumulate_delta(Delta :: map() | undefined) -> ok. +accumulate_delta(Delta) when is_map(Delta) -> + is_enabled() andalso couch_srt_server:update_counters(get_pid_ref(), Delta), + ok; +accumulate_delta(undefined) -> + ok. + +-spec make_delta() -> maybe_delta(). +make_delta() -> + case is_enabled() of + false -> + undefined; + true -> + couch_srt_util:make_delta(get_pid_ref()) + end. + +-spec rctx_delta(TA :: maybe_rctx(), TB :: maybe_rctx()) -> maybe_delta(). +rctx_delta(TA, TB) -> + couch_srt_util:rctx_delta(TA, TB). + +%% +%% Aggregate Query API +%% + +-spec active() -> [rctx()]. +active() -> + couch_srt_query:active(). + +-spec active(Type :: json) -> [rctx()]. +active(Type) -> + couch_srt_query:active(Type). + +-spec active_coordinators() -> [coordinator_rctx()]. +active_coordinators() -> + couch_srt_query:active_coordinators(). + +%% TODO: cleanup json logic here +-spec active_coordinators(Type :: json) -> [coordinator_rctx()]. +active_coordinators(Type) -> + couch_srt_query:active_coordinators(Type). + +-spec active_workers() -> [rpc_worker_rctx()]. +active_workers() -> + couch_srt_query:active_workers(). + +-spec active_workers(Type :: json) -> [rpc_worker_rctx()]. +active_workers(Type) -> + couch_srt_query:active_workers(Type). + +find_by_nonce(Nonce) -> + couch_srt_query:find_by_nonce(Nonce). + +find_by_pid(Pid) -> + couch_srt_query:find_by_pid(Pid). + +find_by_pidref(PidRef) -> + couch_srt_query:find_by_pidref(PidRef). + +find_workers_by_pidref(PidRef) -> + couch_srt_query:find_workers_by_pidref(PidRef). + +-spec pid_ref_matchspec(AttrName :: rctx_field()) -> term() | throw(any()). +pid_ref_matchspec(AttrName) -> + couch_srt_logger:pid_ref_matchspec(AttrName). + +-spec pid_ref_attrs(AttrName :: rctx_field()) -> term() | throw(any()). +pid_ref_attrs(AttrName) -> + couch_srt_logger:pid_ref_attrs(AttrName). + +%% This is a recon:proc_window/3 [1] port with the same core logic but +%% recon_lib:proc_attrs/1 replaced with couch_srt_logger:pid_ref_attrs/1, and +%% returning on pid_ref() rather than pid(). +%% [1] https://github.com/ferd/recon/blob/c2a76855be3a226a3148c0dfc21ce000b6186ef8/src/recon.erl#L268-L300 +-spec proc_window(AttrName, Num, Time) -> term() | throw(any()) when + AttrName :: rctx_field(), Num :: non_neg_integer(), Time :: pos_integer(). +proc_window(AttrName, Num, Time) -> + couch_srt_logger:proc_window(AttrName, Num, Time). + +-spec query_matcher(MatcherName :: matcher_name()) -> + {ok, query_result()} + | {error, any()}. +query_matcher(MatcherName) -> + couch_srt_query:query_matcher(MatcherName). + +-spec query_matcher(MatcherName :: matcher_name(), Limit :: pos_integer()) -> + {ok, query_result()} + | {error, any()}. +query_matcher(MatcherName, Limit) -> + couch_srt_query:query_matcher(MatcherName, Limit). + +%% +%% Delta API +%% + +-spec add_delta(T :: term(), Delta :: maybe_delta()) -> term_delta(). +add_delta(T, Delta) -> + couch_srt_util:add_delta(T, Delta). + +-spec extract_delta(T :: term_delta()) -> {term(), maybe_delta()}. +extract_delta(T) -> + couch_srt_util:extract_delta(T). + +-spec get_delta() -> tagged_delta(). +get_delta() -> + couch_srt_util:get_delta(get_pid_ref()). + +-spec maybe_add_delta(T :: term()) -> term_delta(). +maybe_add_delta(T) -> + couch_srt_util:maybe_add_delta(T). + +-spec maybe_add_delta(T :: term(), Delta :: maybe_delta()) -> term_delta(). +maybe_add_delta(T, Delta) -> + couch_srt_util:maybe_add_delta(T, Delta). + +%% +%% Query API functions +%% +%% + +%% @doc Construct query from the expressions. +%% There are following types of expressions allowed in the query. +%% <li>group_by/1 @see group_by/1</li> +%% <li>group_by/2 @see group_by/1</li> +%% <li>sort_by/1 @see sort_by/1</li> +%% <li>count_by/1 @see count_by/1</li> +%% <li>options/1 @see options/1</li> +%% <li>from/1 @see from/1</li> +%% The order of expressions doesn't matter. +%% <code> +%% Q = query([ +%% from("docs_read"), +%% group_by(username, dbname, ioq_calls), +%% options([ +%% with_limit(10) +%% ]) +%% ]), +%% </code> +%% @end +-spec query(QueryExpression :: [query_expression()]) -> + query() | {error, any()}. +query(QueryExpression) -> + couch_srt_query:query(QueryExpression). + +%% @doc Specify the matcher to use for the query. +%% If atom 'all' is used then all entries would be in the scope of the query. +%% Also the use of 'all' makes the query 'unsafe'. Because it scans through all entries +%% and can return many matching rows. +%% Unsafe queries can only be run using 'unsafe_run/1'. +%% <code> +%% Q = query([ +%% ... +%% from("docs_read") +%% ]), +%% </code> +%% @end +-spec from(MatcherNameOrAll :: string() | all) -> + query_expression() | {error, any()}. +from(MatcherNameOrAll) -> + couch_srt_query:from(MatcherNameOrAll). + +%% @doc Request 'group_by' aggregation of results. +%% <code> +%% Q = query([ +%% ... +%% group_by([username, dbname]) +%% ]), +%% </code> +%% @end +-spec group_by(AggregationKeys) -> + query_expression() | {error, any()} +when + AggregationKeys :: + binary() + | rctx_field() + | [binary()] + | [rctx_field()]. +group_by(AggregationKeys) -> + couch_srt_query:group_by(AggregationKeys). + +%% @doc Request 'group_by' aggregation of results. +%% <code> +%% Q = query([ +%% ... +%% group_by([username, dbname], ioq_calls) +%% ]), +%% </code> +%% @end +-spec group_by(AggregationKeys, ValueKey) -> + query_expression() | {error, any()} +when + AggregationKeys :: + binary() + | rctx_field() + | [binary()] + | [rctx_field()], + ValueKey :: + binary() + | rctx_field(). +group_by(AggregationKeys, ValueKey) -> + couch_srt_query:group_by(AggregationKeys, ValueKey). + +%% @doc Request 'sort_by' aggregation of results. +%% <code> +%% Q = query([ +%% ... +%% sort_by([username, dbname]) +%% ]), +%% </code> +%% @end +-spec sort_by(AggregationKeys) -> + query_expression() | {error, any()} +when + AggregationKeys :: + binary() + | rctx_field() + | [binary()] + | [rctx_field()]. +sort_by(AggregationKeys) -> + couch_srt_query:sort_by(AggregationKeys). + +%% @doc Request 'sort_by' aggregation of results. +%% <code> +%% Q = query([ +%% ... +%% sort_by([username, dbname], ioq_calls) +%% ]), +%% </code> +%% @end +-spec sort_by(AggregationKeys, ValueKey) -> + query_expression() | {error, any()} +when + AggregationKeys :: + binary() + | rctx_field() + | [binary()] + | [rctx_field()], + ValueKey :: + binary() + | rctx_field(). +sort_by(AggregationKeys, ValueKey) -> + couch_srt_query:sort_by(AggregationKeys, ValueKey). + +%% @doc Request 'count_by' aggregation of results. +%% <code> +%% Q = query([ +%% ... +%% count_by(username) +%% ]), +%% </code> +%% @end +-spec count_by(AggregationKeys) -> + query_expression() | {error, any()} +when + AggregationKeys :: + binary() + | rctx_field() + | [binary()] + | [rctx_field()]. +count_by(AggregationKeys) -> + couch_srt_query:count_by(AggregationKeys). + +%% @doc Construct 'options' query expression. +%% There are following types of expressions allowed in the query. +%% <li>unlimited/0 @see unlimited/0 (cannot be used with 'with_limit/1')</li> +%% <li>with_limit/1 @see with_limit/1 (cannot be used with 'unlimited/0')</li> +%% The order of expressions doesn't matter. +%% <code> +%% Q = query([ +%% ... +%% options([ +%% ... +%% ]) +%% ]), +%% </code> +%% @end +-spec options([query_option()]) -> + query_expression() | {error, any()}. +options(OptionsExpression) -> + couch_srt_query:options(OptionsExpression). + +%% @doc Enable unlimited number of results from the query. +%% The use of 'unlimited' makes the query 'unsafe'. Because it can return many matching rows. +%% Unsafe queries can only be run using 'unsafe_run/1'. +%% <code> +%% Q = query([ +%% ... +%% options([ +%% unlimited() +%% ]) +%% ]), +%% </code> +%% @end +-spec unlimited() -> + query_expression(). +unlimited() -> + couch_srt_query:unlimited(). + +%% @doc Set limit on number of results returned from the query. +%% The construction of the query fail if the 'limit' is greater than +%% allowed for this cluster. +%% <code> +%% Q = query([ +%% ... +%% options([ +%% with_limit(100) +%% ]) +%% ]), +%% </code> +%% @end +-spec with_limit(Limit :: pos_integer()) -> + query_expression() | {error, any()}. +with_limit(Limit) -> + couch_srt_query:with_limit(Limit). + +%% @doc Executes provided query. Only 'safe' queries can be executed using 'run'. +%% The query considered 'unsafe' if any of the conditions bellow are met: +%% <li>Query uses 'unlimited/0'</li> +%% <li>Query uses 'from(all)'</li> +%% <code> +%% Q = query([ +%% from("docs_read"), +%% group_by(username, dbname, ioq_calls), +%% options([ +%% with_limit(10) +%% ]) +%% ]), +%% run(Q) +%% </code> +%% @end +-spec run(query()) -> + {ok, [{aggregation_key(), pos_integer()}]} + | {limit, [{aggregation_key(), pos_integer()}]}. +run(Query) -> Review Comment: At first sight this seems like overkill for an off-to-the-side stats aggregator API meant to be called by a server admin operator to figure out their resource usage. I can see this being needed for a public-facing high rate API like changes or all_docs but here overcomplicates things. Maybe just let the operator pass in a `limit` parameter and have single handler function? -- This is an automated message from the Apache Git Service. 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