Simpler and safer db open/closing in view group servers

This makes the opening and closing of databases in the view
group server to be more friendly with the db reference counting
system, avoiding more potential db file leaking after compaction,
as we currently open a database in one process and use it on
another process (view compactor, view updater).

This significantly reduces the chances of failure when compacting
very large views as discussed in COUCHDB-994.

This relates to COUCHDB-926 and COUCHDB-994.




git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@1138796 13f79535-47bb-0310-9956-ffa450edef68

src/couchdb/couch_db.hrl

@@ -225,7 +225,6 @@
 
 -record(group, {
     sig=nil,
-    db=nil,
     fd=nil,
     name,
     def_lang,

src/couchdb/couch_view_compactor.erl

@@ -20,14 +20,14 @@
 %% @doc Compacts the views.  GroupId must not include the _design/ prefix
 start_compact(DbName, GroupId) ->
     Pid = couch_view:get_group_server(DbName, <<"_design/",GroupId/binary>>),
-    gen_server:cast(Pid, {start_compact, fun compact_group/2}).
+    gen_server:cast(Pid, {start_compact, fun compact_group/3}).
 
 %%=============================================================================
 %% internal functions
 %%=============================================================================
 
 %% @spec compact_group(Group, NewGroup) -> ok
-compact_group(Group, EmptyGroup) ->
+compact_group(Group, EmptyGroup, DbName) ->
     #group{
         current_seq = Seq,
         id_btree = IdBtree,
@@ -36,16 +36,16 @@ compact_group(Group, EmptyGroup) ->
     } = Group,
 
     #group{
-        db = Db,
         id_btree = EmptyIdBtree,
         views = EmptyViews
     } = EmptyGroup,
 
+    {ok, Db} = couch_db:open_int(DbName, []),
     {ok, DbReduce} = couch_btree:full_reduce(Db#db.fulldocinfo_by_id_btree),
+    couch_db:close(Db),
     Count = element(1, DbReduce),
 
     <<"_design", ShortName/binary>> = GroupId,
-    DbName = couch_db:name(Db),
     TaskName = <<DbName/binary, ShortName/binary>>,
     couch_task_status:add_task(<<"View Group Compaction">>, TaskName, <<"">>),
     BufferSize = list_to_integer(

src/couchdb/couch_view_group.erl

@@ -78,7 +78,7 @@ start_link(InitArgs) ->
 init({{_, DbName, _} = InitArgs, ReturnPid, Ref}) ->
     process_flag(trap_exit, true),
     try prepare_group(InitArgs, false) of
-    {ok, #group{db=Db, fd=Fd, current_seq=Seq}=Group} ->
+    {ok, Db, #group{fd=Fd, current_seq=Seq}=Group} ->
         case Seq > couch_db:get_update_seq(Db) of
         true ->
             ReturnPid ! {Ref, self(), {error, invalid_view_seq}},
@@ -90,7 +90,7 @@ init({{_, DbName, _} = InitArgs, ReturnPid, Ref}) ->
             {ok, #group_state{
                     db_name=DbName,
                     init_args=InitArgs,
-                    group=Group#group{db=nil},
+                    group=Group,
                     ref_counter=RefCounter}}
         end;
     Error ->
@@ -124,14 +124,11 @@ handle_call({request_group, RequestSeq}, From,
             updater_pid=nil,
             waiting_list=WaitList
             }=State) when RequestSeq > Seq ->
-    {ok, Db} = couch_db:open_int(DbName, []),
-    Group2 = Group#group{db=Db},
     Owner = self(),
-    Pid = spawn_link(fun()-> couch_view_updater:update(Owner, Group2) end),
+    Pid = spawn_link(fun()-> couch_view_updater:update(Owner, Group, DbName) end),
 
     {noreply, State#group_state{
         updater_pid=Pid,
-        group=Group2,
         waiting_list=[{From,RequestSeq}|WaitList]
         }, infinity};
 
@@ -166,7 +163,8 @@ handle_cast({start_compact, CompactFun}, #group_state{compactor_pid=nil}
     {ok, Db} = couch_db:open_int(DbName, []),
     {ok, Fd} = open_index_file(compact, RootDir, DbName, GroupSig),
     NewGroup = reset_file(Db, Fd, DbName, Group),
-    Pid = spawn_link(fun() -> CompactFun(Group, NewGroup) end),
+    couch_db:close(Db),
+    Pid = spawn_link(fun() -> CompactFun(Group, NewGroup, DbName) end),
     {noreply, State#group_state{compactor_pid = Pid}};
 handle_cast({start_compact, _}, State) ->
     %% compact already running, this is a no-op
@@ -176,7 +174,7 @@ handle_cast({compact_done, #group{current_seq=NewSeq} = NewGroup},
         #group_state{group = #group{current_seq=OldSeq}} = State)
         when NewSeq >= OldSeq ->
     #group_state{
-        group = #group{name=GroupId, fd=OldFd, sig=GroupSig} = Group,
+        group = #group{name=GroupId, fd=OldFd, sig=GroupSig},
         init_args = {RootDir, DbName, _},
         updater_pid = UpdaterPid,
         compactor_pid = CompactorPid,
@@ -195,7 +193,7 @@ handle_cast({compact_done, #group{current_seq=NewSeq} = NewGroup},
         unlink(UpdaterPid),
         exit(UpdaterPid, view_compaction_complete),
         Owner = self(),
-        spawn_link(fun()-> couch_view_updater:update(Owner, NewGroup) end);
+        spawn_link(fun()-> couch_view_updater:update(Owner, NewGroup, DbName) end);
     true ->
         nil
     end,
@@ -206,19 +204,10 @@ handle_cast({compact_done, #group{current_seq=NewSeq} = NewGroup},
     unlink(OldFd),
     couch_ref_counter:drop(RefCounter),
     {ok, NewRefCounter} = couch_ref_counter:start([NewGroup#group.fd]),
-    case Group#group.db of
-        nil -> ok;
-        Else -> couch_db:close(Else)
-    end,
-
-    case NewGroup#group.db of
-        nil -> ok;
-        _ -> couch_db:close(NewGroup#group.db)
-    end,
 
     self() ! delayed_commit,
     {noreply, State#group_state{
-        group=NewGroup#group{db = nil},
+        group=NewGroup,
         ref_counter=NewRefCounter,
         compactor_pid=nil,
         updater_pid=NewUpdaterPid
@@ -230,18 +219,15 @@ handle_cast({compact_done, NewGroup}, State) ->
     } = State,
     ?LOG_INFO("View index compaction still behind for ~s ~s -- current: ~p " ++
         "compact: ~p", [DbName, GroupId, CurrentSeq, NewGroup#group.current_seq]),
-    couch_db:close(NewGroup#group.db),
     Pid = spawn_link(fun() ->
-        {ok, Db} = couch_db:open_int(DbName, []),
         {_,Ref} = erlang:spawn_monitor(fun() ->
-            couch_view_updater:update(nil, NewGroup#group{db = Db})
+            couch_view_updater:update(nil, NewGroup, DbName)
         end),
         receive
             {'DOWN', Ref, _, _, {new_group, NewGroup2}} ->
-                couch_db:close(Db),
                 #group{name=GroupId} = NewGroup2,
                 Pid2 = couch_view:get_group_server(DbName, GroupId),
-                gen_server:cast(Pid2, {compact_done, NewGroup2#group{db = nil}})
+                gen_server:cast(Pid2, {compact_done, NewGroup2})
         end
     end),
     {noreply, State#group_state{compactor_pid = Pid}};
@@ -283,44 +269,40 @@ handle_info(delayed_commit, #group_state{db_name=DbName,group=Group}=State) ->
         {noreply, State#group_state{waiting_commit=true}}
     end;
 
-handle_info({'EXIT', FromPid, {new_group, #group{db=Db}=Group}},
+handle_info({'EXIT', FromPid, {new_group, Group}},
         #group_state{db_name=DbName,
             updater_pid=UpPid,
             ref_counter=RefCounter,
             waiting_list=WaitList,
             waiting_commit=WaitingCommit}=State) when UpPid == FromPid ->
-    ok = couch_db:close(Db),
     if not WaitingCommit ->
         erlang:send_after(1000, self(), delayed_commit);
     true -> ok
     end,
     case reply_with_group(Group, WaitList, [], RefCounter) of
     [] ->
         {noreply, State#group_state{waiting_commit=true, waiting_list=[],
-                group=Group#group{db=nil}, updater_pid=nil}};
+                group=Group, updater_pid=nil}};
     StillWaiting ->
         % we still have some waiters, reopen the database and reupdate the index
-        {ok, Db2} = couch_db:open_int(DbName, []),
-        Group2 = Group#group{db=Db2},
         Owner = self(),
-        Pid = spawn_link(fun() -> couch_view_updater:update(Owner, Group2) end),
+        Pid = spawn_link(fun() -> couch_view_updater:update(Owner, Group, DbName) end),
         {noreply, State#group_state{waiting_commit=true,
-                waiting_list=StillWaiting, group=Group2, updater_pid=Pid}}
+                waiting_list=StillWaiting, updater_pid=Pid}}
     end;
 handle_info({'EXIT', _, {new_group, _}}, State) ->
     %% message from an old (probably pre-compaction) updater; ignore
     {noreply, State};
 
-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),
+handle_info({'EXIT', UpPid, reset},
+        #group_state{init_args=InitArgs, updater_pid=UpPid} = State) ->
     case prepare_group(InitArgs, true) of
-    {ok, ResetGroup} ->
+    {ok, Db, ResetGroup} ->
         Owner = self(),
-        Pid = spawn_link(fun()-> couch_view_updater:update(Owner, ResetGroup) end),
+        couch_db:close(Db),
+        Pid = spawn_link(fun() ->
+            couch_view_updater:update(Owner, ResetGroup, Db#db.name)
+        end),
         {noreply, State#group_state{
                 updater_pid=Pid,
                 group=ResetGroup}};
@@ -386,15 +368,15 @@ prepare_group({RootDir, DbName, #group{sig=Sig}=Group}, ForceReset)->
         {ok, Fd} ->
             if ForceReset ->
                 % this can happen if we missed a purge
-                {ok, reset_file(Db, Fd, DbName, Group)};
+                {ok, Db, reset_file(Db, Fd, DbName, Group)};
             true ->
                 case (catch couch_file:read_header(Fd)) of
                 {ok, {Sig, HeaderInfo}} ->
                     % sigs match!
-                    {ok, init_group(Db, Fd, Group, HeaderInfo)};
+                    {ok, Db, init_group(Db, Fd, Group, HeaderInfo)};
                 _ ->
                     % this happens on a new file
-                    {ok, reset_file(Db, Fd, DbName, Group)}
+                    {ok, Db, reset_file(Db, Fd, DbName, Group)}
                 end
             end;
         Error ->
@@ -598,7 +580,7 @@ design_doc_to_view_group(#doc{id=Id,body={Fields}}) ->
 
 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,
+    Group#group{fd=nil,query_server=nil,current_seq=0,
             id_btree=nil,views=Views2}.
 
 reset_file(Db, Fd, DbName, #group{sig=Sig,name=Name} = Group) ->
@@ -656,5 +638,5 @@ init_group(Db, Fd, #group{def_lang=Lang,views=Views}=
             View#view{btree=Btree, update_seq=USeq, purge_seq=PSeq}
         end,
         ViewStates2, Views),
-    Group#group{db=Db, fd=Fd, current_seq=Seq, purge_seq=PurgeSeq,
+    Group#group{fd=Fd, current_seq=Seq, purge_seq=PurgeSeq,
         id_btree=IdBtree, views=Views2}.

src/couchdb/couch_view_updater.erl

@@ -12,30 +12,31 @@
 
 -module(couch_view_updater).
 
--export([update/2]).
+-export([update/3]).
 
 -include("couch_db.hrl").
 
--spec update(_, #group{}) -> no_return().
+-spec update(_, #group{}, Dbname::binary()) -> no_return().
 
-update(Owner, Group) ->
+update(Owner, Group, DbName) ->
     #group{
-        db = #db{name=DbName} = Db,
         name = GroupName,
         current_seq = Seq,
         purge_seq = PurgeSeq
     } = Group,
     couch_task_status:add_task(<<"View Group Indexer">>, <<DbName/binary," ",GroupName/binary>>, <<"Starting index update">>),
 
+    {ok, Db} = couch_db:open_int(DbName, []),
     DbPurgeSeq = couch_db:get_purge_seq(Db),
     Group2 =
     if DbPurgeSeq == PurgeSeq ->
         Group;
     DbPurgeSeq == PurgeSeq + 1 ->
         couch_task_status:update(<<"Removing purged entries from view index.">>),
-        purge_index(Group);
+        purge_index(Group, Db);
     true ->
         couch_task_status:update(<<"Resetting view index due to lost purge entries.">>),
+        couch_db:close(Db),
         exit(reset)
     end,
     {ok, MapQueue} = couch_work_queue:new(
@@ -73,13 +74,14 @@ update(Owner, Group) ->
     couch_task_status:set_update_frequency(0),
     couch_task_status:update("Finishing."),
     couch_work_queue:close(MapQueue),
+    couch_db:close(Db),
     receive {new_group, NewGroup} ->
         exit({new_group,
                 NewGroup#group{current_seq=couch_db:get_update_seq(Db)}})
     end.
 
 
-purge_index(#group{db=Db, views=Views, id_btree=IdBtree}=Group) ->
+purge_index(#group{views=Views, id_btree=IdBtree}=Group, Db) ->
     {ok, PurgedIdsRevs} = couch_db:get_last_purged(Db),
     Ids = [Id || {Id, _Revs} <- PurgedIdsRevs],
     {ok, Lookups, IdBtree2} = couch_btree:query_modify(IdBtree, Ids, [], Ids),