Delete attachments when no longer referenced

This fixes attachment handling to properly remove attachment data when
it is no longer referenced by the document's revision tree.

As implemented this accounts for the possibility that multiple revisions
may reference a given attachment id. However, due to how the current
revision tree removes revisions aggressively it's not currently possible
for multiple leaf revisions to share an underlying attachment. This is
because when attempting to use a stub attachment when replicating in a
conflict we will encounter the `missing_stub` error because the previous
shared revision has already been removed.

5 files changed, 428 insertions, 20 deletions

diff --git a/src/fabric/include/fabric2.hrl b/src/fabric/include/fabric2.hrl
index 189995de2..b4dd084a2 100644
--- a/src/fabric/include/fabric2.hrl
+++ b/src/fabric/include/fabric2.hrl
@@ -37,12 +37,15 @@
 -define(DB_ATTS, 23).
 -define(DB_VIEWS, 24).
 -define(DB_LOCAL_DOC_BODIES, 25).
+-define(DB_ATT_NAMES, 26).
 
 
 % Versions
 
--define(CURR_REV_FORMAT, 0).
+% 0 - Initial implementation
+% 1 - Added attachment hash
 
+-define(CURR_REV_FORMAT, 1).
 
 % Misc constants
 
diff --git a/src/fabric/src/fabric2_db.erl b/src/fabric/src/fabric2_db.erl
index 88840e702..6d015df0e 100644
--- a/src/fabric/src/fabric2_db.erl
+++ b/src/fabric/src/fabric2_db.erl
@@ -1341,7 +1341,8 @@ update_doc_interactive(Db, Doc0, Future, _Options) ->
 
     #doc{
         deleted = NewDeleted,
-        revs = {NewRevPos, [NewRev | NewRevPath]}
+        revs = {NewRevPos, [NewRev | NewRevPath]},
+        atts = Atts
     } = Doc4 = stem_revisions(Db, Doc3),
 
     NewRevInfo = #{
@@ -1350,7 +1351,8 @@ update_doc_interactive(Db, Doc0, Future, _Options) ->
         rev_id => {NewRevPos, NewRev},
         rev_path => NewRevPath,
         sequence => undefined,
-        branch_count => undefined
+        branch_count => undefined,
+        att_hash => fabric2_util:hash_atts(Atts)
     },
 
     % Gather the list of possible winnig revisions
@@ -1405,7 +1407,8 @@ update_doc_replicated(Db, Doc0, _Options) ->
         rev_id => {RevPos, Rev},
         rev_path => RevPath,
         sequence => undefined,
-        branch_count => undefined
+        branch_count => undefined,
+        att_hash => <<>>
     },
 
     AllRevInfos = fabric2_fdb:get_all_revs(Db, DocId),
@@ -1444,6 +1447,9 @@ update_doc_replicated(Db, Doc0, _Options) ->
     PrevRevInfo = find_prev_revinfo(RevPos, LeafPath),
     Doc2 = prep_and_validate(Db, Doc1, PrevRevInfo),
     Doc3 = flush_doc_atts(Db, Doc2),
+    DocRevInfo2 = DocRevInfo1#{
+        atts_hash => fabric2_util:hash_atts(Doc3#doc.atts)
+    },
 
     % Possible winners are the previous winner and
     % the new DocRevInfo
@@ -1453,9 +1459,9 @@ update_doc_replicated(Db, Doc0, _Options) ->
     end,
     {NewWinner0, NonWinner} = case Winner == PrevRevInfo of
         true ->
-            {DocRevInfo1, not_found};
+            {DocRevInfo2, not_found};
         false ->
-            [W, NW] = fabric2_util:sort_revinfos([Winner, DocRevInfo1]),
+            [W, NW] = fabric2_util:sort_revinfos([Winner, DocRevInfo2]),
             {W, NW}
     end,
 
diff --git a/src/fabric/src/fabric2_fdb.erl b/src/fabric/src/fabric2_fdb.erl
index fb2891be7..404460ed5 100644
--- a/src/fabric/src/fabric2_fdb.erl
+++ b/src/fabric/src/fabric2_fdb.erl
@@ -580,9 +580,40 @@ write_doc(#{} = Db0, Doc, NewWinner0, OldWinner, ToUpdate, ToRemove) ->
 
     #doc{
         id = DocId,
-        deleted = Deleted
+        deleted = Deleted,
+        atts = Atts
     } = Doc,
 
+    % Doc body
+
+    ok = write_doc_body(Db, Doc),
+
+    % Attachment bookkeeping
+
+    % If a document's attachments have changed we have to scan
+    % for any attachments that may need to be deleted. The check
+    % for `>= 2` is a bit subtle. The important point is that
+    % one of the revisions will be from the new document so we
+    % have to find at least one more beyond that to assert that
+    % the attachments have not changed.
+    AttHash = fabric2_util:hash_atts(Atts),
+    RevsToCheck = [NewWinner0] ++ ToUpdate ++ ToRemove,
+    AttHashCount = lists:foldl(fun(Att, Count) ->
+        #{att_hash := RevAttHash} = Att,
+        case RevAttHash == AttHash of
+            true -> Count + 1;
+            false -> Count
+        end
+    end, 0, RevsToCheck),
+    if
+        AttHashCount == length(RevsToCheck) ->
+            ok;
+        AttHashCount >= 2 ->
+            ok;
+        true ->
+            cleanup_attachments(Db, DocId, Doc, ToRemove)
+    end,
+
     % Revision tree
 
     NewWinner = NewWinner0#{winner := true},
@@ -649,8 +680,6 @@ write_doc(#{} = Db0, Doc, NewWinner0, OldWinner, ToUpdate, ToRemove) ->
 
     % And all the rest...
 
-    ok = write_doc_body(Db, Doc),
-
     IsDDoc = case Doc#doc.id of
         <<?DESIGN_DOC_PREFIX, _/binary>> -> true;
         _ -> false
@@ -755,6 +784,9 @@ write_attachment(#{} = Db, DocId, Data) when is_binary(Data) ->
     AttId = fabric2_util:uuid(),
     Chunks = chunkify_binary(Data),
 
+    IdKey = erlfdb_tuple:pack({?DB_ATT_NAMES, DocId, AttId}, DbPrefix),
+    ok = erlfdb:set(Tx, IdKey, <<>>),
+
     lists:foldl(fun(Chunk, ChunkId) ->
         AttKey = erlfdb_tuple:pack({?DB_ATTS, DocId, AttId, ChunkId}, DbPrefix),
         ok = erlfdb:set(Tx, AttKey, Chunk),
@@ -1014,16 +1046,71 @@ clear_doc_body(#{} = Db, DocId, #{} = RevInfo) ->
     ok = erlfdb:clear_range(Tx, StartKey, EndKey).
 
 
+cleanup_attachments(Db, DocId, NewDoc, ToRemove) ->
+    #{
+        tx := Tx,
+        db_prefix := DbPrefix
+    } = Db,
+
+    RemoveRevs = lists:map(fun(#{rev_id := RevId}) -> RevId end, ToRemove),
+
+    % Gather all known document revisions
+    {ok, DiskDocs} = fabric2_db:open_doc_revs(Db, DocId, all, []),
+    AllDocs = [{ok, NewDoc} | DiskDocs],
+
+    % Get referenced attachment ids
+    ActiveIdSet = lists:foldl(fun({ok, Doc}, Acc) ->
+        #doc{
+            revs = {Pos, [Rev | _]}
+        } = Doc,
+        case lists:member({Pos, Rev}, RemoveRevs) of
+            true ->
+                Acc;
+            false ->
+                lists:foldl(fun(Att, InnerAcc) ->
+                    {loc, _Db, _DocId, AttId} = couch_att:fetch(data, Att),
+                    sets:add_element(AttId, InnerAcc)
+                end, Acc, Doc#doc.atts)
+        end
+    end, sets:new(), AllDocs),
+
+    AttPrefix = erlfdb_tuple:pack({?DB_ATT_NAMES, DocId}, DbPrefix),
+    Options = [{streaming_mode, want_all}],
+    Future = erlfdb:get_range_startswith(Tx, AttPrefix, Options),
+
+    ExistingIdSet = lists:foldl(fun({K, _}, Acc) ->
+        {?DB_ATT_NAMES, DocId, AttId} = erlfdb_tuple:unpack(K, DbPrefix),
+        sets:add_element(AttId, Acc)
+    end, sets:new(), erlfdb:wait(Future)),
+
+    AttsToRemove = sets:subtract(ExistingIdSet, ActiveIdSet),
+
+    lists:foreach(fun(AttId) ->
+        IdKey = erlfdb_tuple:pack({?DB_ATT_NAMES, DocId, AttId}, DbPrefix),
+        erlfdb:clear(Tx, IdKey),
+
+        ChunkKey = erlfdb_tuple:pack({?DB_ATTS, DocId, AttId}, DbPrefix),
+        erlfdb:clear_range_startswith(Tx, ChunkKey)
+    end, sets:to_list(AttsToRemove)).
+
+
 revinfo_to_fdb(Tx, DbPrefix, DocId, #{winner := true} = RevId) ->
     #{
         deleted := Deleted,
         rev_id := {RevPos, Rev},
         rev_path := RevPath,
-        branch_count := BranchCount
+        branch_count := BranchCount,
+        att_hash := AttHash
     } = RevId,
     VS = new_versionstamp(Tx),
     Key = {?DB_REVS, DocId, not Deleted, RevPos, Rev},
-    Val = {?CURR_REV_FORMAT, VS, BranchCount, list_to_tuple(RevPath)},
+    Val = {
+        ?CURR_REV_FORMAT,
+        VS,
+        BranchCount,
+        list_to_tuple(RevPath),
+        AttHash
+    },
     KBin = erlfdb_tuple:pack(Key, DbPrefix),
     VBin = erlfdb_tuple:pack_vs(Val),
     {KBin, VBin, VS};
@@ -1032,38 +1119,49 @@ revinfo_to_fdb(_Tx, DbPrefix, DocId, #{} = RevId) ->
     #{
         deleted := Deleted,
         rev_id := {RevPos, Rev},
-        rev_path := RevPath
+        rev_path := RevPath,
+        att_hash := AttHash
     } = RevId,
     Key = {?DB_REVS, DocId, not Deleted, RevPos, Rev},
-    Val = {?CURR_REV_FORMAT, list_to_tuple(RevPath)},
+    Val = {?CURR_REV_FORMAT, list_to_tuple(RevPath), AttHash},
     KBin = erlfdb_tuple:pack(Key, DbPrefix),
     VBin = erlfdb_tuple:pack(Val),
     {KBin, VBin, undefined}.
 
 
-fdb_to_revinfo(Key, {?CURR_REV_FORMAT, _, _, _} = Val) ->
+fdb_to_revinfo(Key, {?CURR_REV_FORMAT, _, _, _, _} = Val) ->
     {?DB_REVS, _DocId, NotDeleted, RevPos, Rev} = Key,
-    {_RevFormat, Sequence, BranchCount, RevPath} = Val,
+    {_RevFormat, Sequence, BranchCount, RevPath, AttHash} = Val,
     #{
         winner => true,
         deleted => not NotDeleted,
         rev_id => {RevPos, Rev},
         rev_path => tuple_to_list(RevPath),
         sequence => Sequence,
-        branch_count => BranchCount
+        branch_count => BranchCount,
+        att_hash => AttHash
     };
 
-fdb_to_revinfo(Key, {?CURR_REV_FORMAT, _} = Val)  ->
+fdb_to_revinfo(Key, {?CURR_REV_FORMAT, _, _} = Val)  ->
     {?DB_REVS, _DocId, NotDeleted, RevPos, Rev} = Key,
-    {_RevFormat, RevPath} = Val,
+    {_RevFormat, RevPath, AttHash} = Val,
     #{
         winner => false,
         deleted => not NotDeleted,
         rev_id => {RevPos, Rev},
         rev_path => tuple_to_list(RevPath),
         sequence => undefined,
-        branch_count => undefined
-    }.
+        branch_count => undefined,
+        att_hash => AttHash
+    };
+
+fdb_to_revinfo(Key, {0, Seq, BCount, RPath}) ->
+    Val = {?CURR_REV_FORMAT, Seq, BCount, RPath, <<>>},
+    fdb_to_revinfo(Key, Val);
+
+fdb_to_revinfo(Key, {0, RPath}) ->
+    Val = {?CURR_REV_FORMAT, RPath, <<>>},
+    fdb_to_revinfo(Key, Val).
 
 
 doc_to_fdb(Db, #doc{} = Doc) ->
diff --git a/src/fabric/src/fabric2_util.erl b/src/fabric/src/fabric2_util.erl
index 2b8e49ebf..4e2e2d76b 100644
--- a/src/fabric/src/fabric2_util.erl
+++ b/src/fabric/src/fabric2_util.erl
@@ -25,6 +25,8 @@
 
     validate_security_object/1,
 
+    hash_atts/1,
+
     dbname_ends_with/2,
 
     get_value/2,
@@ -124,6 +126,20 @@ validate_json_list_of_strings(Member, Props) ->
     end.
 
 
+hash_atts([]) ->
+    <<>>;
+
+hash_atts(Atts) ->
+    SortedAtts = lists:sort(fun(A, B) ->
+        couch_att:fetch(name, A) =< couch_att:fetch(name, B)
+    end, Atts),
+    Md5St = lists:foldl(fun(Att, Acc) ->
+        {loc, _Db, _DocId, AttId} = couch_att:fetch(data, Att),
+        couch_hash:md5_hash_update(Acc, AttId)
+    end, couch_hash:md5_hash_init(), SortedAtts),
+    couch_hash:md5_hash_final(Md5St).
+
+
 dbname_ends_with(#{} = Db, Suffix) ->
     dbname_ends_with(fabric2_db:name(Db), Suffix);
 
diff --git a/src/fabric/test/fabric2_doc_att_tests.erl b/src/fabric/test/fabric2_doc_att_tests.erl
new file mode 100644
index 000000000..331e1a4e8
--- /dev/null
+++ b/src/fabric/test/fabric2_doc_att_tests.erl
@@ -0,0 +1,285 @@
+% 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(fabric2_doc_att_tests).
+
+
+-include_lib("couch/include/couch_db.hrl").
+-include_lib("couch/include/couch_eunit.hrl").
+-include_lib("eunit/include/eunit.hrl").
+-include("fabric2.hrl").
+-include("fabric2_test.hrl").
+
+
+doc_crud_test_() ->
+    {
+        "Test document CRUD operations",
+        {
+            setup,
+            fun setup/0,
+            fun cleanup/1,
+            with([
+                ?TDEF(create_att),
+                ?TDEF(delete_att),
+                ?TDEF(multiple_atts),
+                ?TDEF(delete_one_att),
+                ?TDEF(large_att),
+                ?TDEF(att_on_conflict_isolation)
+            ])
+        }
+    }.
+
+
+setup() ->
+    Ctx = test_util:start_couch([fabric]),
+    {ok, Db} = fabric2_db:create(?tempdb(), [{user_ctx, ?ADMIN_USER}]),
+    {Db, Ctx}.
+
+
+cleanup({Db, Ctx}) ->
+    ok = fabric2_db:delete(fabric2_db:name(Db), []),
+    test_util:stop_couch(Ctx).
+
+
+create_att({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    Att1 = couch_att:new([
+        {name, <<"foo.txt">>},
+        {type, <<"application/octet-stream">>},
+        {att_len, 6},
+        {data, <<"foobar">>},
+        {encoding, identity},
+        {md5, <<>>}
+    ]),
+    Doc1 = #doc{
+        id = DocId,
+        atts = [Att1]
+    },
+    {ok, _} = fabric2_db:update_doc(Db, Doc1),
+    {ok, Doc2} = fabric2_db:open_doc(Db, DocId),
+    #doc{
+        atts = [Att2]
+    } = Doc2,
+    {loc, _Db, DocId, AttId} = couch_att:fetch(data, Att2),
+    AttData = fabric2_db:read_attachment(Db, DocId, AttId),
+    ?assertEqual(<<"foobar">>, AttData),
+
+    % Check that the raw keys exist
+    #{
+        db_prefix := DbPrefix
+    } = Db,
+    IdKey = erlfdb_tuple:pack({?DB_ATT_NAMES, DocId, AttId}, DbPrefix),
+    AttKey = erlfdb_tuple:pack({?DB_ATTS, DocId, AttId}, DbPrefix),
+
+    fabric2_fdb:transactional(fun(Tx) ->
+        IdVal = erlfdb:wait(erlfdb:get(Tx, IdKey)),
+        AttVals = erlfdb:wait(erlfdb:get_range_startswith(Tx, AttKey)),
+
+        ?assertEqual(<<>>, IdVal),
+        ?assertMatch([{_, <<"foobar">>}], AttVals)
+    end).
+
+
+delete_att({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    Att1 = couch_att:new([
+        {name, <<"foo.txt">>},
+        {type, <<"application/octet-stream">>},
+        {att_len, 6},
+        {data, <<"foobar">>},
+        {encoding, identity},
+        {md5, <<>>}
+    ]),
+    Doc1 = #doc{
+        id = DocId,
+        atts = [Att1]
+    },
+    {ok, _} = fabric2_db:update_doc(Db, Doc1),
+    {ok, Doc2} = fabric2_db:open_doc(Db, DocId),
+    #doc{
+        atts = [Att2]
+    } = Doc2,
+    {loc, _Db, DocId, AttId} = couch_att:fetch(data, Att2),
+
+    Doc3 = Doc2#doc{atts = []},
+    {ok, _} = fabric2_db:update_doc(Db, Doc3),
+
+    {ok, Doc4} = fabric2_db:open_doc(Db, DocId),
+    ?assertEqual([], Doc4#doc.atts),
+
+    % Check that the raw keys were removed
+    #{
+        db_prefix := DbPrefix
+    } = Db,
+    IdKey = erlfdb_tuple:pack({?DB_ATT_NAMES, DocId, AttId}, DbPrefix),
+    AttKey = erlfdb_tuple:pack({?DB_ATTS, DocId, AttId}, DbPrefix),
+
+    fabric2_fdb:transactional(fun(Tx) ->
+        IdVal = erlfdb:wait(erlfdb:get(Tx, IdKey)),
+        AttVals = erlfdb:wait(erlfdb:get_range_startswith(Tx, AttKey)),
+
+        ?assertEqual(not_found, IdVal),
+        ?assertMatch([], AttVals)
+    end).
+
+
+multiple_atts({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    Atts = [
+        mk_att(<<"foo.txt">>, <<"foobar">>),
+        mk_att(<<"bar.txt">>, <<"barfoo">>),
+        mk_att(<<"baz.png">>, <<"blargh">>)
+    ],
+    {ok, _} = create_doc(Db, DocId, Atts),
+    ?assertEqual(
+            #{
+                <<"foo.txt">> => <<"foobar">>,
+                <<"bar.txt">> => <<"barfoo">>,
+                <<"baz.png">> => <<"blargh">>
+            },
+            read_atts(Db, DocId)
+        ).
+
+
+delete_one_att({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    Atts1 = [
+        mk_att(<<"foo.txt">>, <<"foobar">>),
+        mk_att(<<"bar.txt">>, <<"barfoo">>),
+        mk_att(<<"baz.png">>, <<"blargh">>)
+    ],
+    {ok, RevId} = create_doc(Db, DocId, Atts1),
+    Atts2 = tl(Atts1),
+    {ok, _} = update_doc(Db, DocId, RevId, stubify(RevId, Atts2)),
+    ?assertEqual(
+            #{
+                <<"bar.txt">> => <<"barfoo">>,
+                <<"baz.png">> => <<"blargh">>
+            },
+            read_atts(Db, DocId)
+        ).
+
+
+large_att({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    % Total size ~360,000 bytes
+    AttData = iolist_to_binary([
+        <<"foobar">> || _ <- lists:seq(1, 60000)
+    ]),
+    Att1 = mk_att("long.txt", AttData),
+    {ok, _} = create_doc(Db, DocId, [Att1]),
+    ?assertEqual(#{"long.txt" => AttData}, read_atts(Db, DocId)),
+
+    {ok, Doc} = fabric2_db:open_doc(Db, DocId),
+    #doc{atts = [Att2]} = Doc,
+    {loc, _Db, DocId, AttId} = couch_att:fetch(data, Att2),
+
+    #{db_prefix := DbPrefix} = Db,
+    AttKey = erlfdb_tuple:pack({?DB_ATTS, DocId, AttId}, DbPrefix),
+    fabric2_fdb:transactional(fun(Tx) ->
+        AttVals = erlfdb:wait(erlfdb:get_range_startswith(Tx, AttKey)),
+        ?assertEqual(4, length(AttVals))
+    end).
+
+
+att_on_conflict_isolation({Db, _}) ->
+    DocId = fabric2_util:uuid(),
+    [PosRevA1, PosRevB1] = create_conflicts(Db, DocId, []),
+    Att = mk_att(<<"happy_goat.tiff">>, <<":D>">>),
+    {ok, PosRevA2} = update_doc(Db, DocId, PosRevA1, [Att]),
+    ?assertEqual(
+            #{<<"happy_goat.tiff">> => <<":D>">>},
+            read_atts(Db, DocId, PosRevA2)
+        ),
+    ?assertEqual(#{}, read_atts(Db, DocId, PosRevB1)).
+
+
+mk_att(Name, Data) ->
+    couch_att:new([
+        {name, Name},
+        {type, <<"application/octet-stream">>},
+        {att_len, size(Data)},
+        {data, Data},
+        {encoding, identity},
+        {md5, <<>>}
+    ]).
+
+
+stubify(RevId, Atts) when is_list(Atts) ->
+    lists:map(fun(Att) ->
+        stubify(RevId, Att)
+    end, Atts);
+
+stubify({Pos, _Rev}, Att) ->
+    couch_att:store([
+        {data, stub},
+        {revpos, Pos}
+    ], Att).
+
+
+create_doc(Db, DocId, Atts) ->
+    Doc = #doc{
+        id = DocId,
+        atts = Atts
+    },
+    fabric2_db:update_doc(Db, Doc).
+
+
+update_doc(Db, DocId, {Pos, Rev}, Atts) ->
+    Doc = #doc{
+        id = DocId,
+        revs = {Pos, [Rev]},
+        atts = Atts
+    },
+    fabric2_db:update_doc(Db, Doc).
+
+
+create_conflicts(Db, DocId, Atts) ->
+    Base = #doc{
+        id = DocId,
+        atts = Atts
+    },
+    {ok, {_, Rev1} = PosRev} = fabric2_db:update_doc(Db, Base),
+    <<Rev2:16/binary, Rev3:16/binary>> = fabric2_util:uuid(),
+    Doc1 = #doc{
+        id = DocId,
+        revs = {2, [Rev2, Rev1]},
+        atts = stubify(PosRev, Atts)
+    },
+    Doc2 = #doc{
+        id = DocId,
+        revs = {2, [Rev3, Rev1]},
+        atts = stubify(PosRev, Atts)
+    },
+    {ok, _} = fabric2_db:update_doc(Db, Doc1, [replicated_changes]),
+    {ok, _} = fabric2_db:update_doc(Db, Doc2, [replicated_changes]),
+    lists:reverse(lists:sort([{2, Rev2}, {2, Rev3}])).
+
+
+read_atts(Db, DocId) ->
+    {ok, #doc{atts = Atts}} = fabric2_db:open_doc(Db, DocId),
+    atts_to_map(Db, DocId, Atts).
+
+
+read_atts(Db, DocId, PosRev) ->
+    {ok, Docs} = fabric2_db:open_doc_revs(Db, DocId, [PosRev], []),
+    [{ok, #doc{atts = Atts}}] = Docs,
+    atts_to_map(Db, DocId, Atts).
+
+
+atts_to_map(Db, DocId, Atts) ->
+    lists:foldl(fun(Att, Acc) ->
+        [Name, Data] = couch_att:fetch([name, data], Att),
+        {loc, _Db, DocId, AttId} = Data,
+        AttBin = fabric2_db:read_attachment(Db, DocId, AttId),
+        maps:put(Name, AttBin, Acc)
+    end, #{}, Atts).