% 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_view_group). -behaviour(gen_server). %% API -export([start_link/1, request_group/2]). -export([design_doc_to_view_group/1]). %% gen_server callbacks -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]). -include("couch_db.hrl"). -record(group_state, { type, db_name, init_args, group, updater_pid=nil, waiting_commit=false, waiting_list=[] }). % api methods request_group(Pid, Seq) -> ?LOG_DEBUG("request_group {Pid, Seq} ~p", [{Pid, Seq}]), case gen_server:call(Pid, {request_group, Seq}, infinity) of {ok, Group} -> {ok, Group}; Else -> ?LOG_DEBUG("get_updated_group replied with _Else ~p", [Else]), Else end. % from template start_link(InitArgs) -> case gen_server:start_link(couch_view_group, {InitArgs, self(), Ref = make_ref()}, []) of {ok, Pid} -> {ok, Pid}; ignore -> receive {Ref, Pid, Error} -> case process_info(self(), trap_exit) of {trap_exit, true} -> receive {'EXIT', Pid, _} -> ok end; {trap_exit, false} -> ok end, Error end; Error -> Error end. % init differentiates between temp and design_doc views. It creates a closure % which spawns the appropriate view_updater. (It might also spawn the first % view_updater run.) init({InitArgs, ReturnPid, Ref}) -> process_flag(trap_exit, true), case prepare_group(InitArgs, false) of {ok, #group{db=Db}=Group} -> couch_db:monitor(Db), Pid = spawn_link(fun()-> couch_view_updater:update(Group) end), {ok, #group_state{ db_name=couch_db:name(Db), init_args=InitArgs, updater_pid = Pid, group=Group}}; Error -> ReturnPid ! {Ref, self(), Error}, ignore end. % There are two sources of messages: couch_view, which requests an up to date % view group, and the couch_view_updater, which when spawned, updates the % group and sends it back here. We employ a caching mechanism, so that between % database writes, we don't have to spawn a couch_view_updater with every view % request. This should give us more control, and the ability to request view % statuses eventually. % The caching mechanism: each request is submitted with a seq_id for the % database at the time it was read. We guarantee to return a view from that % sequence or newer. % If the request sequence is higher than our current high_target seq, we set % that as the highest seqence. If the updater is not running, we launch it. handle_call({request_group, RequestSeq}, From, #group_state{ db_name=DbName, group=#group{current_seq=Seq}=Group, updater_pid=nil, waiting_list=WaitList }=State) when RequestSeq > Seq -> {ok, Db} = couch_db:open(DbName, []), Group2 = Group#group{db=Db}, Pid = spawn_link(fun()-> couch_view_updater:update(Group2) end), {noreply, State#group_state{ updater_pid=Pid, group=Group2, waiting_list=[{From,RequestSeq}|WaitList] }, infinity}; % If the request seqence is less than or equal to the seq_id of a known Group, % we respond with that Group. handle_call({request_group, RequestSeq}, _From, #group_state{group=#group{current_seq=GroupSeq}=Group}=State) when RequestSeq =< GroupSeq -> {reply, {ok, Group}, State}; % Otherwise: TargetSeq => RequestSeq > GroupSeq % We've already initiated the appropriate action, so just hold the response until the group is up to the RequestSeq handle_call({request_group, RequestSeq}, From, #group_state{waiting_list=WaitList}=State) -> {noreply, State#group_state{ waiting_list=[{From, RequestSeq}|WaitList] }, infinity}. handle_cast(foo, State) -> {ok, State}. handle_info(delayed_commit, #group_state{db_name=DbName,group=Group}=State) -> {ok, Db} = couch_db:open(DbName, []), CommittedSeq = couch_db:get_committed_update_seq(Db), couch_db:close(Db), if CommittedSeq >= Group#group.current_seq -> % save the header Header = {Group#group.sig, get_index_header_data(Group)}, ok = couch_file:write_header(Group#group.fd, <<$r, $c, $k, 0>>, Header), {noreply, State#group_state{waiting_commit=false}}; true -> % We can't commit the header because the database seq that's fully % committed to disk is still behind us. If we committed now and the % database lost those changes our view could be forever out of sync % with the database. But a crash before we commit these changes, no big % deal, we only lose incremental changes since last committal. erlang:send_after(1000, self(), delayed_commit), {noreply, State#group_state{waiting_commit=true}} end; handle_info({'EXIT', FromPid, {new_group, #group{db=Db}=Group}}, #group_state{db_name=DbName, updater_pid=UpPid, waiting_list=WaitList, waiting_commit=WaitingCommit}=State) when UpPid == FromPid -> ok = couch_db:close(Db), if Group#group.type == view andalso not WaitingCommit -> erlang:send_after(1000, self(), delayed_commit); true -> ok end, case reply_with_group(Group, WaitList, []) of [] -> {noreply, State#group_state{waiting_commit=true, waiting_list=[], group=Group#group{db=nil}, updater_pid=nil}}; StillWaiting -> % we still have some waiters, reopen the database and reupdate the index {ok, Db2} = couch_db:open(DbName, []), Group2 = Group#group{db=Db2}, Pid = spawn_link(fun() -> couch_view_updater:update(Group2) end), {noreply, State#group_state{waiting_commit=true, waiting_list=StillWaiting, group=Group2, updater_pid=Pid}} end; handle_info({'EXIT', FromPid, reset}, #group_state{ init_args=InitArgs, updater_pid=UpPid, group=Group}=State) when UpPid == FromPid -> ok = couch_db:close(Group#group.db), case prepare_group(InitArgs, true) of {ok, ResetGroup} -> Pid = spawn_link(fun()-> couch_view_updater:update(ResetGroup) end), {noreply, State#group_state{ updater_pid=Pid, group=ResetGroup}}; Error -> {stop, normal, reply_all(State, Error)} end; handle_info({'EXIT', _FromPid, normal}, State) -> {noreply, State}; handle_info({'EXIT', FromPid, Reason}, State) -> ?LOG_DEBUG("Exit from linked pid: ~p", [{FromPid, Reason}]), {stop, Reason, State}; handle_info({'DOWN',_,_,_,_}, State) -> ?LOG_INFO("Shutting down view group server, monitored db is closing.", []), {stop, normal, reply_all(State, shutdown)}. terminate(Reason, State) -> reply_all(State, Reason), ok. code_change(_OldVsn, State, _Extra) -> {ok, State}. %% Local Functions % reply_with_group/3 % for each item in the WaitingList {Pid, Seq} % if the Seq is =< GroupSeq, reply reply_with_group(Group=#group{current_seq=GroupSeq}, [{Pid, Seq}|WaitList], StillWaiting) when Seq =< GroupSeq -> gen_server:reply(Pid, {ok, Group}), reply_with_group(Group, WaitList, StillWaiting); % else % put it in the continuing waiting list reply_with_group(Group, [{Pid, Seq}|WaitList], StillWaiting) -> reply_with_group(Group, WaitList, [{Pid, Seq}|StillWaiting]); % return the still waiting list reply_with_group(_Group, [], StillWaiting) -> StillWaiting. reply_all(#group_state{waiting_list=WaitList}=State, Reply) -> [catch gen_server:reply(Pid, Reply) || {Pid, _} <- WaitList], State#group_state{waiting_list=[]}. prepare_group({view, RootDir, DbName, GroupId}, ForceReset)-> case open_db_group(DbName, GroupId) of {ok, Db, #group{sig=Sig}=Group} -> case open_index_file(RootDir, DbName, GroupId) of {ok, Fd} -> if ForceReset -> {ok, reset_file(Db, Fd, DbName, Group)}; true -> case (catch couch_file:read_header(Fd, <<$r, $c, $k, 0>>)) of {ok, {Sig, HeaderInfo}} -> % sigs match! {ok, init_group(Db, Fd, Group, HeaderInfo)}; _ -> {ok, reset_file(Db, Fd, DbName, Group)} end end; Error -> catch delete_index_file(RootDir, DbName, GroupId), Error end; Error -> catch delete_index_file(RootDir, DbName, GroupId), Error end; prepare_group({slow_view, DbName, Fd, Lang, DesignOptions, MapSrc, RedSrc}, _ForceReset) -> case couch_db:open(DbName, []) of {ok, Db} -> View = #view{map_names=[<<"_temp">>], id_num=0, btree=nil, def=MapSrc, reduce_funs= if RedSrc==[] -> []; true -> [{<<"_temp">>, RedSrc}] end}, {ok, init_group(Db, Fd, #group{type=slow_view, name= <<"_temp">>, db=Db, views=[View], def_lang=Lang, design_options=DesignOptions}, nil)}; Error -> Error end. get_index_header_data(#group{current_seq=Seq, purge_seq=PurgeSeq, id_btree=IdBtree,views=Views}) -> ViewStates = [couch_btree:get_state(Btree) || #view{btree=Btree} <- Views], #index_header{seq=Seq, purge_seq=PurgeSeq, id_btree_state=couch_btree:get_state(IdBtree), view_states=ViewStates}. open_index_file(RootDir, DbName, GroupId) -> FileName = RootDir ++ "/." ++ ?b2l(DbName) ++ ?b2l(GroupId) ++".view", case couch_file:open(FileName) of {ok, Fd} -> {ok, Fd}; {error, enoent} -> couch_file:open(FileName, [create]); Error -> Error end. open_db_group(DbName, GroupId) -> case couch_db:open(DbName, []) of {ok, Db} -> case couch_db:open_doc(Db, GroupId) of {ok, Doc} -> {ok, Db, design_doc_to_view_group(Doc)}; Else -> couch_db:close(Db), Else end; Else -> Else end. % maybe move to another module design_doc_to_view_group(#doc{id=Id,body={Fields}}) -> Language = proplists:get_value(<<"language">>, Fields, <<"javascript">>), {DesignOptions} = proplists:get_value(<<"options">>, Fields, {[]}), {RawViews} = proplists:get_value(<<"views">>, Fields, {[]}), % add the views to a dictionary object, with the map source as the key DictBySrc = lists:foldl( fun({Name, {MRFuns}}, DictBySrcAcc) -> MapSrc = proplists:get_value(<<"map">>, MRFuns), RedSrc = proplists:get_value(<<"reduce">>, MRFuns, null), View = case dict:find(MapSrc, DictBySrcAcc) of {ok, View0} -> View0; error -> #view{def=MapSrc} % create new view object end, View2 = if RedSrc == null -> View#view{map_names=[Name|View#view.map_names]}; true -> View#view{reduce_funs=[{Name,RedSrc}|View#view.reduce_funs]} end, dict:store(MapSrc, View2, DictBySrcAcc) end, dict:new(), RawViews), % number the views {Views, _N} = lists:mapfoldl( fun({_Src, View}, N) -> {View#view{id_num=N},N+1} end, 0, dict:to_list(DictBySrc)), Group = #group{name=Id, views=Views, def_lang=Language, design_options=DesignOptions}, Group#group{sig=erlang:md5(term_to_binary(Group))}. reset_group(#group{views=Views}=Group) -> Views2 = [View#view{btree=nil} || View <- Views], Group#group{db=nil,fd=nil,query_server=nil,current_seq=0, id_btree=nil,views=Views2}. reset_file(Db, Fd, DbName, #group{sig=Sig,name=Name} = Group) -> ?LOG_DEBUG("Reseting group index \"~s\" in db ~s", [Name, DbName]), ok = couch_file:truncate(Fd, 0), ok = couch_file:write_header(Fd, <<$r, $c, $k, 0>>, {Sig, nil}), init_group(Db, Fd, reset_group(Group), nil). delete_index_file(RootDir, DbName, GroupId) -> file:delete(RootDir ++ "/." ++ binary_to_list(DbName) ++ binary_to_list(GroupId) ++ ".view"). init_group(Db, Fd, #group{views=Views}=Group, nil) -> init_group(Db, Fd, Group, #index_header{seq=0, purge_seq=couch_db:get_purge_seq(Db), id_btree_state=nil, view_states=[nil || _ <- Views]}); init_group(Db, Fd, #group{def_lang=Lang,views=Views}=Group, IndexHeader) -> #index_header{seq=Seq, purge_seq=PurgeSeq, id_btree_state=IdBtreeState, view_states=ViewStates} = IndexHeader, {ok, IdBtree} = couch_btree:open(IdBtreeState, Fd), Views2 = lists:zipwith( fun(BtreeState, #view{reduce_funs=RedFuns}=View) -> FunSrcs = [FunSrc || {_Name, FunSrc} <- RedFuns], ReduceFun = fun(reduce, KVs) -> KVs2 = couch_view:expand_dups(KVs,[]), KVs3 = couch_view:detuple_kvs(KVs2,[]), {ok, Reduced} = couch_query_servers:reduce(Lang, FunSrcs, KVs3), {length(KVs3), Reduced}; (rereduce, Reds) -> Count = lists:sum([Count0 || {Count0, _} <- Reds]), UserReds = [UserRedsList || {_, UserRedsList} <- Reds], {ok, Reduced} = couch_query_servers:rereduce(Lang, FunSrcs, UserReds), {Count, Reduced} end, {ok, Btree} = couch_btree:open(BtreeState, Fd, [{less, fun couch_view:less_json_keys/2}, {reduce, ReduceFun}]), View#view{btree=Btree} end, ViewStates, Views), Group#group{db=Db, fd=Fd, current_seq=Seq, purge_seq=PurgeSeq, id_btree=IdBtree, views=Views2}.