nickva commented on code in PR #4201: URL: https://github.com/apache/couchdb/pull/4201#discussion_r998902080
########## src/fabric/src/fabric_open_revs.erl: ########## @@ -0,0 +1,481 @@ +% 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(fabric_open_revs). + +-export([ + go/3 +]). + +-include_lib("mem3/include/mem3.hrl"). +-include_lib("couch/include/couch_db.hrl"). + +-record(req, { + idrevs, + wcnt = 0, + rcnt = 0, + responses = [] +}). + +-record(st, { + r, + args, + reqs, + workers +}). + +go(_DbName, [], _Options) -> + {ok, []}; +go(DbName, IdsRevsOpts, Options) -> + St = init_state(DbName, IdsRevsOpts, Options), + WShards = maps:keys(St#st.workers), + RexiMon = fabric_util:create_monitors(WShards), + try fabric_util:recv(WShards, #shard.ref, fun handle_message/3, St) of + {timeout, #st{workers = #{} = Workers1}} -> + stop_workers(Workers1), + fabric_util:log_timeout(maps:keys(Workers1), "open_revs"), + {error, timeout}; + Else -> + Else + after + rexi_monitor:stop(RexiMon) + end. + +handle_message([_ | _] = Resps, Worker, #st{} = St) -> + #st{workers = Workers, reqs = Reqs, r = R} = St, + {ArgsRefs, Workers1} = maps:take(Worker, Workers), + ArgsResps = lists:zip(ArgsRefs, Resps), + Reqs1 = lists:foldl(fun responses_fold/2, Reqs, ArgsResps), + case not r_met(Reqs1, R) andalso have_viable_workers(Workers1) of + true -> + {ok, St#st{workers = Workers1, reqs = Reqs1}}; + false -> + stop_workers(Workers1), + {stop, finalize(St#st.args, Reqs1)} + end; +handle_message({rexi_DOWN, _, {_, NodeRef}, _}, _Worker, #st{} = St) -> + #st{workers = Workers, reqs = Reqs} = St, + FilterFun = fun(#shard{node = N}) -> N =:= NodeRef end, + DeadKeys = lists:filter(FilterFun, maps:keys(Workers)), + Workers1 = maps:without(DeadKeys, Workers), + DeadWorkers = maps:with(DeadKeys, Workers), + FoldFun = fun(_, ArgRefs, Acc) -> update_wcnt(Acc, ArgRefs, -1) end, + Reqs1 = maps:fold(FoldFun, Reqs, DeadWorkers), + Error = {error, {nodedown, <<"progress not possible">>}}, + handle_error(Error, St#st{workers = Workers1, reqs = Reqs1}); +handle_message({rexi_EXIT, Reason}, Worker, #st{} = St) -> + handle_message(Reason, Worker, St); +handle_message({error, Reason}, Worker, #st{} = St) -> + handle_message(Reason, Worker, St); +handle_message(Reason, Worker, #st{} = St) -> + #st{workers = Workers, reqs = Reqs} = St, + {DeadArgRefs, Workers1} = maps:take(Worker, Workers), + Reqs1 = update_wcnt(Reqs, DeadArgRefs, -1), + handle_error(Reason, St#st{workers = Workers1, reqs = Reqs1}). + +init_state(DbName, IdsRevsOpts, Options) -> + DefaultR = integer_to_list(mem3:quorum(DbName)), + R = list_to_integer(couch_util:get_value(r, Options, DefaultR)), + {ArgRefs, Reqs0} = build_req_map(IdsRevsOpts), + ShardMap = build_worker_map(DbName, Reqs0), + {Workers, Reqs} = spawn_workers(Reqs0, ShardMap, Options), + #st{r = R, args = ArgRefs, reqs = Reqs, workers = Workers}. + +responses_fold({ArgRef, NewResp}, #{} = Reqs) -> + #{ArgRef := Req} = Reqs, + #req{rcnt = R, wcnt = W, responses = Resps} = Req, + Resps1 = merge_responses(Resps, NewResp), + % If responses don't match or are "not found", don't bump rcnt so we can + % wait for more workers. + OldLen = length(Resps), + NewLen = length(Resps1), + NewR = + case {is_not_found(NewResp), OldLen} of + {true, _} -> R; + {_, 0} -> R + 1; + {_, L} when L == NewLen -> R + 1; + {_, L} when L < NewLen -> R + end, + Reqs#{ + ArgRef => Req#req{ + rcnt = NewR, + wcnt = W - 1, + responses = Resps1 + } + }. + +handle_error(Error, #st{workers = Workers, reqs = Reqs} = St) -> + case success_possible(Reqs) of + true -> + case have_viable_workers(Workers) of + true -> + {ok, St}; + false -> + % Don't have a choice, have to stop + {stop, finalize(St#st.args, Reqs)} + end; + false -> + stop_workers(Workers), + {error, Error} + end. + +% De-duplicate identical responses as we go along +% +merge_responses(Responses, Response) -> + Fun = fun(A, B) -> sort_key(A) =< sort_key(B) end, + lists:umerge(Fun, Responses, lists:usort(Fun, Response)). + +% Assuming docs in most cases will be identical, so check their revs and other +% metadata and avoid checking their body, which can be quite a bit a larger, +% just to figure they are actually the same. +% +sort_key({ok, #doc{id = Id, revs = Revs, deleted = Deleted}}) -> + {Revs, Deleted, Id}; +sort_key(NotFound) -> + NotFound. + +% Build a #{ArgRef => #req{}} map. ArgRef references the initial {{Id, Revs}, +% Opts} tuples and the #req{} is a record keeping track of response for just +% that {Id, Revs} pair. +% +build_req_map(IdsRevsOpts) -> + Fun = fun(IdRevsOpts, Acc) -> + ArgRef = make_ref(), + {ArgRef, Acc#{ArgRef => #req{idrevs = IdRevsOpts}}} + end, + lists:mapfoldr(Fun, #{}, IdsRevsOpts). + +% Build a #{#shard{} => [ArgRef1, ArgRef2, ...]} map. This structure will be +% used for launching workers and then matching up response with the original +% args. +% +build_worker_map(DbName, #{} = Reqs) -> + FoldReqsFun = fun(ArgRef, #req{idrevs = IdRevs}, WAcc) -> + {{DocId, _}, _} = IdRevs, + FoldShardsFun = fun(Shard, WAccInner) -> + UpdateFun = fun(ArgRefs) -> [ArgRef | ArgRefs] end, + maps:update_with(Shard, UpdateFun, [ArgRef], WAccInner) + end, + lists:foldl(FoldShardsFun, WAcc, mem3:shards(DbName, DocId)) + end, + maps:fold(FoldReqsFun, #{}, Reqs). + +spawn_workers(#{} = Reqs, #{} = ShardMap, Options) -> + Fun = fun(Shard, ArgRefs, {WAcc, ReqsAcc}) -> + Worker = rexi_cast(Shard, ArgRefs, ReqsAcc, Options), + WAcc1 = WAcc#{Worker => ArgRefs}, + ReqsAcc1 = update_wcnt(ReqsAcc, ArgRefs, 1), + {WAcc1, ReqsAcc1} + end, + maps:fold(Fun, {#{}, Reqs}, ShardMap). + +% Spawn a worker and return an updated #shard{} with worker ref +% Args are fetched from the Reqs map based on the ArgRef tag +% +rexi_cast(#shard{} = Shard, ArgRefs, #{} = Reqs, Options) -> + Fun = fun(ArgRef) when is_reference(ArgRef) -> + #{ArgRef := #req{idrevs = IdRevs}} = Reqs, + IdRevs + end, + Args = lists:map(Fun, ArgRefs), + RexiArgs = {fabric_rpc, open_revs, [Shard#shard.name, Args, Options]}, + WRef = rexi:cast(Shard#shard.node, RexiArgs), + Shard#shard{ref = WRef}. + +% Update worker count for each of the #req{} records. Value may be positive +% or negative, which could be used to decrement worker counts +% +update_wcnt(#{} = Reqs, ArgRefs, Val) when is_integer(Val) -> + Fun = fun(Ref, Acc) -> + #{Ref := #req{wcnt = W} = Req} = Acc, + Acc#{Ref => Req#req{wcnt = W + Val}} + end, + lists:foldl(Fun, Reqs, ArgRefs). + +% Return true if we still have any outstanding workers we could wait on +% +have_viable_workers(#{} = Workers) -> + map_size(Workers) > 0. + +% We can still return success if we either have some waiting workers, or at +% least one response already each {Id, Revs} pair. +% +success_possible(#{} = Reqs) -> + Fun = fun(_, #req{wcnt = W, rcnt = R}, Acc) -> Acc andalso W + R > 0 end, + maps:fold(Fun, true, Reqs). + +r_met(#{} = Reqs, ExpectedR) -> + Fun = fun(_, #req{rcnt = R}, Acc) -> min(R, Acc) end, + maps:fold(Fun, ExpectedR, Reqs) >= ExpectedR. + +finalize(ArgRefs, #{} = Reqs) -> + Fun = fun(Ref) -> + #{Ref := #req{responses = Resps}} = Reqs, + finalize_req(Resps) + end, + lists:map(Fun, ArgRefs). + +finalize_req(DocRevs) -> + Paths = lists:map(fun rev_to_path/1, DocRevs), + RevTree = couch_key_tree:multi_merge([], Paths), + TreeLeafs = couch_key_tree:get_all_leafs(RevTree), + lists:map(fun path_to_reply/1, TreeLeafs). + +path_to_reply({?REV_MISSING, {Pos, [Rev]}}) -> + {{not_found, missing}, {Pos, Rev}}; +path_to_reply({#doc{} = Doc, _}) -> + {ok, Doc}. + +is_not_found([]) -> + true; +is_not_found([_ | _] = Revs) -> + Fun = fun + ({{not_found, missing}, {_, _}}) -> true; + (_) -> false + end, + lists:any(Fun, Revs). + +rev_to_path({ok, #doc{} = Doc}) -> + couch_doc:to_path(Doc); +rev_to_path({{not_found, missing}, {Pos, Rev}}) -> + {Pos, {Rev, ?REV_MISSING, []}}. + +stop_workers(#{} = Workers) -> + Fun = fun(#shard{node = Node, ref = Ref}) -> {Node, Ref} end, + NodeRefs = lists:map(Fun, maps:keys(Workers)), + rexi:kill_all(NodeRefs). + +-ifdef(TEST). +-include_lib("couch/include/couch_eunit.hrl"). + +setup_all() -> + config:start_link([]), + meck:new([fabric, couch_stats, couch_log]), + meck:new(rexi, [passthrough]), + meck:new(mem3, [passthrough]), + meck:new(fabric_util, [passthrough]), + meck:expect(fabric, update_docs, fun(_, _, _) -> {ok, nil} end), + meck:expect(mem3, quorum, fun(_) -> 2 end), + meck:expect(mem3, shards, fun(<<"db">>, <<"a">>) -> + [#shard{node = 'n1'}, #shard{node = 'n2'}, #shard{node = 'n3'}] + end), + meck:expect(couch_stats, increment_counter, fun(_) -> ok end), + meck:expect(couch_log, notice, fun(_, _) -> ok end), + meck:expect(rexi, cast, fun(_, _) -> make_ref() end), + meck:expect(rexi, kill_all, fun(_) -> ok end). + +teardown_all(_) -> + meck:unload(), + config:stop(). + +setup() -> + meck:reset([ + couch_log, + mem3, + rexi, + couch_stats, + fabric, + fabric_util + ]). + +teardown(_) -> + ok. + +st0() -> + IdRevsOpts = [{{<<"a">>, all}, []}], + init_state(<<"db">>, IdRevsOpts, []). + +foo1() -> {ok, #doc{revs = {1, [<<"foo">>]}}}. +foo2() -> {ok, #doc{revs = {2, [<<"foo2">>, <<"foo">>]}}}. +foo2stemmed() -> {ok, #doc{revs = {2, [<<"foo2">>]}}}. +bar1() -> {ok, #doc{revs = {1, [<<"bar">>]}}}. +bazNF() -> {{not_found, missing}, {1, <<"baz">>}}. +baz1() -> {ok, #doc{revs = {1, [<<"baz">>]}}}. + +open_revs_quorum_test_() -> + { + setup, + fun setup_all/0, + fun teardown_all/1, + { + foreach, + fun setup/0, + fun teardown/1, + [ + ?TDEF_FE(t_empty_request_gets_an_empty_result), + ?TDEF_FE(t_initial_state), + ?TDEF_FE(t_basic_response), + ?TDEF_FE(t_finish_quorum), + ?TDEF_FE(t_no_quorum_on_different_responses), + ?TDEF_FE(t_no_quorum_on_not_found), + ?TDEF_FE(t_done_on_third), + ?TDEF_FE(t_all_different_responses), + ?TDEF_FE(t_ancestors_merge_correctly), + ?TDEF_FE(t_stemmed_merge_correctly), + ?TDEF_FE(t_not_found_counted_as_descendant), + ?TDEF_FE(t_all_not_found), + ?TDEF_FE(t_rev_not_found_returned), + ?TDEF_FE(t_rexi_errors_progress), + ?TDEF_FE(t_generic_errors_progress), + ?TDEF_FE(t_failure_on_all_errors) + ] + } + }. + +t_empty_request_gets_an_empty_result(_) -> + ?assertEqual({ok, []}, go(<<"foo">>, [], [])). + +t_initial_state(_) -> + % Smoke test that we have setup our state correctly + S0 = st0(), + ?assertMatch(#st{args = [_], r = 2, reqs = #{}, workers = #{}}, S0), + #st{args = ArgsRefs, reqs = Reqs, workers = Workers} = S0, + % The args refs list is the reqs keys + ?assertEqual(lists:sort(ArgsRefs), lists:sort(maps:keys(Reqs))), + % Each worker's args is from the args refs list and there are no args which + % which haven't been assigned to at least one worker. + SpawnedArgs = lists:flatten(maps:values(Workers)), + ?assertEqual(lists:sort(ArgsRefs), lists:usort(SpawnedArgs)), + maps:map( + fun(_, #req{} = Req) -> + % 3 workers were spawned + ?assertEqual(3, Req#req.wcnt), + % no workers have returned yet + ?assertEqual(0, Req#req.rcnt), + % responses is an empty list (since no workers returned yet) + ?assertEqual([], Req#req.responses) + end, + Reqs + ). + +t_basic_response(_) -> + S0 = #st{workers = Workers0} = st0(), + [W1 | _] = lists:sort(maps:keys(Workers0)), + Res = handle_message([[foo1(), bar1()]], W1, S0), + ?assertMatch({ok, #st{}}, Res), + {ok, #st{reqs = Reqs, workers = Workers1}} = Res, + ?assertEqual(2, map_size(Workers1)), + ?assertNot(maps:is_key(W1, Workers1)), + ?assertEqual(1, map_size(Reqs)), + [#req{wcnt = W, rcnt = R}] = maps:values(Reqs), + ?assertEqual(2, W), + ?assertEqual(1, R). + +t_finish_quorum(_) -> + % Two messages with the same revisions means we're done + S0 = #st{workers = Workers0} = st0(), + [W1, W2 | _] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[foo1(), bar1()]], W1, S0), + Res = handle_message([[bar1(), foo1()]], W2, S1), + ?assertEqual({stop, [[foo1(), bar1()]]}, Res). + +t_no_quorum_on_different_responses(_) -> + % Got different revisions, so we're waiting for more workers. + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[foo1(), bar1()]], W1, S0), + Res1 = handle_message([[foo2(), bar1()]], W2, S1), + ?assertMatch({ok, #st{}}, Res1), + {ok, S2} = Res1, + Res2 = handle_message([[foo1(), bar1()]], W3, S2), + ?assertEqual({stop, [[foo2(), bar1()]]}, Res2). + +t_no_quorum_on_not_found(_) -> + % Got a [] (not found), so wait for more workers + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[foo1(), bar1()]], W1, S0), + {ok, S2} = handle_message([[]], W2, S1), + Res2 = handle_message([[foo2(), bar1()]], W3, S2), + ?assertEqual({stop, [[foo2(), bar1()]]}, Res2). + +t_done_on_third(_) -> + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[]], W1, S0), + {ok, S2} = handle_message([[foo2(), bar1()]], W2, S1), + ?assertEqual({stop, [[foo2(), bar1()]]}, handle_message([[]], W3, S2)). + +t_all_different_responses(_) -> + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[bar1()]], W1, S0), + {ok, S2} = handle_message([[foo2(), bar1()]], W2, S1), + Res = handle_message([[foo1(), bazNF()]], W3, S2), + Expect = [[foo2(), bazNF(), bar1()]], + ?assertEqual({stop, Expect}, Res). + +t_ancestors_merge_correctly(_) -> + % Ancestors are merged as internal nodes correctly + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[foo1()]], W1, S0), + {ok, S2} = handle_message([[foo2()]], W2, S1), + ?assertEqual({stop, [[foo2()]]}, handle_message([[]], W3, S2)). + +t_stemmed_merge_correctly(_) -> + % Ancestors are merged as internal nodes correctly + S0 = #st{workers = Workers0} = st0(), + [W1, W2, W3] = lists:sort(maps:keys(Workers0)), + {ok, S1} = handle_message([[foo2()]], W1, S0), + {ok, S2} = handle_message([[foo2stemmed()]], W2, S1), + ?assertEqual({stop, [[foo2(), bar1()]]}, handle_message([[bar1()]], W3, S2)). + +t_not_found_counted_as_descendant(_) -> + % Ancestors are merged as internal nodes correctly Review Comment: Oops. 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