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Diffstat (limited to 'apps/couch/src/couch_rep_reader.erl')
| -rw-r--r-- | apps/couch/src/couch_rep_reader.erl | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/apps/couch/src/couch_rep_reader.erl b/apps/couch/src/couch_rep_reader.erl new file mode 100644 index 00000000..1e8ca074 --- /dev/null +++ b/apps/couch/src/couch_rep_reader.erl @@ -0,0 +1,277 @@ +% 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_rep_reader). +-behaviour(gen_server). +-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, + code_change/3]). + +-export([start_link/4, next/1]). + +-import(couch_util, [encode_doc_id/1]). + +-define (BUFFER_SIZE, 1000). +-define (MAX_CONCURRENT_REQUESTS, 100). + +-include("couch_db.hrl"). + +-record (state, { + parent, + source, + missing_revs, + reader_loop, + reader_from = [], + count = 0, + docs = queue:new(), + reply_to = nil, + complete = false, + monitor_count = 0, + pending_doc_request = nil, + requested_seqs = [], + opened_seqs = [] +}). + +start_link(Parent, Source, MissingRevs, PostProps) -> + gen_server:start_link(?MODULE, [Parent, Source, MissingRevs, PostProps], []). + +next(Pid) -> + gen_server:call(Pid, next_docs, infinity). + +init([Parent, Source, MissingRevs, _PostProps]) -> + process_flag(trap_exit, true), + Self = self(), + ReaderLoop = spawn_link( + fun() -> reader_loop(Self, Parent, Source, MissingRevs) end), + State = #state{ + parent = Parent, + source = Source, + missing_revs = MissingRevs, + reader_loop = ReaderLoop + }, + {ok, State}. + +handle_call({add_docs, Seq, Docs}, From, State) -> + State#state.parent ! {update_stats, docs_read, length(Docs)}, + handle_add_docs(Seq, lists:flatten(Docs), From, State); + +handle_call({add_request_seqs, Seqs}, _From, State) -> + SeqList = State#state.requested_seqs, + {reply, ok, State#state{requested_seqs = lists:merge(Seqs, SeqList)}}; + +handle_call(next_docs, From, State) -> + handle_next_docs(From, State); + +handle_call({open_remote_doc, Id, Seq, Revs}, From, State) -> + handle_open_remote_doc(Id, Seq, Revs, From, State). + +handle_cast(_Msg, State) -> + {noreply, State}. + +handle_info({'DOWN', _, _, _, Reason}, State) -> + handle_monitor_down(Reason, State); + +handle_info({'EXIT', Loop, complete}, #state{reader_loop=Loop} = State) -> + handle_reader_loop_complete(State). + +terminate(_Reason, _State) -> + % ?LOG_INFO("rep reader terminating with reason ~p", [_Reason]), + ok. + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + +%internal funs + +handle_add_docs(_Seq, [], _From, State) -> + {reply, ok, State}; +handle_add_docs(Seq, DocsToAdd, From, #state{reply_to=nil} = State) -> + State1 = update_sequence_lists(Seq, State), + NewState = State1#state{ + docs = queue:join(State1#state.docs, queue:from_list(DocsToAdd)), + count = State1#state.count + length(DocsToAdd) + }, + if NewState#state.count < ?BUFFER_SIZE -> + {reply, ok, NewState}; + true -> + {noreply, NewState#state{reader_from=[From|State#state.reader_from]}} + end; +handle_add_docs(Seq, DocsToAdd, _From, #state{count=0} = State) -> + NewState = update_sequence_lists(Seq, State), + HighSeq = calculate_new_high_seq(NewState), + gen_server:reply(State#state.reply_to, {HighSeq, DocsToAdd}), + {reply, ok, NewState#state{reply_to=nil}}. + +handle_next_docs(From, #state{count=0} = State) -> + if State#state.complete -> + {stop, normal, {complete, calculate_new_high_seq(State)}, State}; + true -> + {noreply, State#state{reply_to=From}} + end; +handle_next_docs(_From, State) -> + #state{ + reader_from = ReaderFrom, + docs = Docs + } = State, + [gen_server:reply(F, ok) || F <- ReaderFrom], + NewState = State#state{count=0, reader_from=[], docs=queue:new()}, + {reply, {calculate_new_high_seq(State), queue:to_list(Docs)}, NewState}. + +handle_open_remote_doc(Id, Seq, Revs, From, #state{monitor_count=N} = State) + when N > ?MAX_CONCURRENT_REQUESTS -> + {noreply, State#state{pending_doc_request={From,Id,Seq,Revs}}}; +handle_open_remote_doc(Id, Seq, Revs, _, #state{source=#http_db{}} = State) -> + #state{ + monitor_count = Count, + source = Source + } = State, + {_, _Ref} = spawn_document_request(Source, Id, Seq, Revs), + {reply, ok, State#state{monitor_count = Count+1}}. + +handle_monitor_down(normal, #state{pending_doc_request=nil, reply_to=nil, + monitor_count=1, complete=waiting_on_monitors} = State) -> + {noreply, State#state{complete=true, monitor_count=0}}; +handle_monitor_down(normal, #state{pending_doc_request=nil, reply_to=From, + monitor_count=1, complete=waiting_on_monitors} = State) -> + gen_server:reply(From, {complete, calculate_new_high_seq(State)}), + {stop, normal, State#state{complete=true, monitor_count=0}}; +handle_monitor_down(normal, #state{pending_doc_request=nil} = State) -> + #state{monitor_count = Count} = State, + {noreply, State#state{monitor_count = Count-1}}; +handle_monitor_down(normal, State) -> + #state{ + source = Source, + pending_doc_request = {From, Id, Seq, Revs} + } = State, + gen_server:reply(From, ok), + {_, _NewRef} = spawn_document_request(Source, Id, Seq, Revs), + {noreply, State#state{pending_doc_request=nil}}; +handle_monitor_down(Reason, State) -> + {stop, Reason, State}. + +handle_reader_loop_complete(#state{reply_to=nil, monitor_count=0} = State) -> + {noreply, State#state{complete = true}}; +handle_reader_loop_complete(#state{monitor_count=0} = State) -> + HighSeq = calculate_new_high_seq(State), + gen_server:reply(State#state.reply_to, {complete, HighSeq}), + {stop, normal, State}; +handle_reader_loop_complete(State) -> + {noreply, State#state{complete = waiting_on_monitors}}. + +calculate_new_high_seq(#state{requested_seqs=[], opened_seqs=[Open|_]}) -> + Open; +calculate_new_high_seq(#state{requested_seqs=[Req|_], opened_seqs=[Open|_]}) + when Req < Open -> + 0; +calculate_new_high_seq(#state{opened_seqs=[]}) -> + 0; +calculate_new_high_seq(State) -> + hd(State#state.opened_seqs). + +split_revlist(Rev, {[CurrentAcc|Rest], BaseLength, Length}) -> + case Length+size(Rev)+3 > 8192 of + false -> + {[[Rev|CurrentAcc] | Rest], BaseLength, Length+size(Rev)+3}; + true -> + {[[Rev],CurrentAcc|Rest], BaseLength, BaseLength} + end. + +% We store outstanding requested sequences and a subset of already opened +% sequences in 2 ordered lists. The subset of opened seqs is a) the largest +% opened seq smaller than the smallest outstanding request seq plus b) all the +% opened seqs greater than the smallest outstanding request. I believe its the +% minimal set of info needed to correctly calculate which seqs have been +% replicated (because remote docs can be opened out-of-order) -- APK +update_sequence_lists(Seq, State) -> + Requested = lists:delete(Seq, State#state.requested_seqs), + AllOpened = lists:merge([Seq], State#state.opened_seqs), + Opened = case Requested of + [] -> + [lists:last(AllOpened)]; + [EarliestReq|_] -> + case lists:splitwith(fun(X) -> X < EarliestReq end, AllOpened) of + {[], Greater} -> + Greater; + {Less, Greater} -> + [lists:last(Less) | Greater] + end + end, + State#state{ + requested_seqs = Requested, + opened_seqs = Opened + }. + +open_doc_revs(#http_db{url = Url} = DbS, DocId, Revs) -> + %% all this logic just splits up revision lists that are too long for + %% MochiWeb into multiple requests + BaseQS = [{revs,true}, {latest,true}, {att_encoding_info,true}], + BaseReq = DbS#http_db{resource=encode_doc_id(DocId), qs=BaseQS}, + BaseLength = length(couch_rep_httpc:full_url(BaseReq) ++ "&open_revs=[]"), + + {RevLists, _, _} = lists:foldl(fun split_revlist/2, + {[[]], BaseLength, BaseLength}, couch_doc:revs_to_strs(Revs)), + + Requests = [BaseReq#http_db{ + qs = [{open_revs, ?JSON_ENCODE(RevList)} | BaseQS] + } || RevList <- RevLists], + JsonResults = lists:flatten([couch_rep_httpc:request(R) || R <- Requests]), + + Transform = + fun({[{<<"ok">>, Json}]}, Acc) -> + #doc{id=Id, revs=Rev, atts=Atts} = Doc = couch_doc:from_json_obj(Json), + Doc1 = Doc#doc{ + atts=[couch_rep_att:convert_stub(A, {DbS,Id,Rev}) || A <- Atts] + }, + [Doc1 | Acc]; + ({ErrorProps}, Acc) -> + Err = couch_util:get_value(<<"error">>, ErrorProps, + ?JSON_ENCODE({ErrorProps})), + ?LOG_ERROR("Replicator: error accessing doc ~s at ~s, reason: ~s", + [DocId, couch_util:url_strip_password(Url), Err]), + Acc + end, + lists:reverse(lists:foldl(Transform, [], JsonResults)). + +reader_loop(ReaderServer, Parent, Source, MissingRevsServer) -> + case couch_rep_missing_revs:next(MissingRevsServer) of + complete -> + exit(complete); + {_HighSeq, IdsRevs} -> + % to be safe, make sure Results are sorted by source_seq + SortedIdsRevs = lists:keysort(2, IdsRevs), + RequestSeqs = [S || {_,S,_} <- SortedIdsRevs], + gen_server:call(ReaderServer, {add_request_seqs, RequestSeqs}, infinity), + case Source of + #http_db{} -> + [gen_server:call(ReaderServer, {open_remote_doc, Id, Seq, Revs}, + infinity) || {Id,Seq,Revs} <- SortedIdsRevs], + reader_loop(ReaderServer, Parent, Source, MissingRevsServer); + _Local -> + {ok, Source2} = couch_db:open( + Source#db.name, [{user_ctx, Source#db.user_ctx}]), + lists:foreach(fun({Id,Seq,Revs}) -> + {ok, Docs} = couch_db:open_doc_revs(Source2, Id, Revs, [latest]), + JustTheDocs = [Doc || {ok, Doc} <- Docs], + gen_server:call(ReaderServer, {add_docs, Seq, JustTheDocs}, + infinity) + end, SortedIdsRevs), + couch_db:close(Source2), + reader_loop(ReaderServer, Parent, Source2, MissingRevsServer) + end + end. + +spawn_document_request(Source, Id, Seq, Revs) -> + Server = self(), + SpawnFun = fun() -> + Results = open_doc_revs(Source, Id, Revs), + gen_server:call(Server, {add_docs, Seq, Results}, infinity) + end, + spawn_monitor(SpawnFun). |