From ed231d0fd1cf7647cc7a154de81e85cd584bc8b5 Mon Sep 17 00:00:00 2001
From: Adam Kocoloski <adam@cloudant.com>
Date: Tue, 19 Oct 2010 17:17:08 -0400
Subject: use new read repair and ancestry checks in fabric:open_doc/3

---
 apps/fabric/src/fabric_doc_open.erl | 101 +++++++++++++++++++++++++-----------
 1 file changed, 70 insertions(+), 31 deletions(-)

(limited to 'apps/fabric')

diff --git a/apps/fabric/src/fabric_doc_open.erl b/apps/fabric/src/fabric_doc_open.erl
index 1530515d..9131c94b 100644
--- a/apps/fabric/src/fabric_doc_open.erl
+++ b/apps/fabric/src/fabric_doc_open.erl
@@ -27,54 +27,93 @@ go(DbName, Id, Options) ->
     R = couch_util:get_value(r, Options, couch_config:get("cluster","r","2")),
     Acc0 = {length(Workers), list_to_integer(R), []},
     case fabric_util:recv(Workers, #shard.ref, fun handle_message/3, Acc0) of
-    {ok, {ok, #doc{deleted=true}}} when SuppressDeletedDoc ->
-        {not_found, deleted};
-    {ok, Else} ->
-        Else;
+    {ok, Reply} ->
+        format_reply(Reply, SuppressDeletedDoc);
+    {error, needs_repair, Reply} ->
+        spawn(fabric, open_revs, [DbName, Id, all, Options]),
+        format_reply(Reply, SuppressDeletedDoc);
+    {error, needs_repair} ->
+        % we couldn't determine the correct reply, so we'll run a sync repair
+        {ok, Results} = fabric:open_revs(DbName, Id, all, Options),
+        case lists:partition(fun({ok, #doc{deleted=Del}}) -> Del end, Results) of
+        {[], []} ->
+            {not_found, missing};
+        {_DeletedDocs, []} when SuppressDeletedDoc ->
+            {not_found, deleted};
+        {DeletedDocs, []} ->
+            lists:last(lists:sort(DeletedDocs));
+        {_, LiveDocs} ->
+            lists:last(lists:sort(LiveDocs))
+        end;
     Error ->
         Error
     end.
 
+format_reply({ok, #doc{deleted=true}}, true) ->
+    {not_found, deleted};
+format_reply(Else, _) ->
+    Else.
+
 handle_message({rexi_DOWN, _, _, _}, _Worker, Acc0) ->
     skip_message(Acc0);
 handle_message({rexi_EXIT, _Reason}, _Worker, Acc0) ->
     skip_message(Acc0);
 handle_message(Reply, _Worker, {WaitingCount, R, Replies}) ->
-    case merge_read_reply(make_key(Reply), Reply, Replies) of
-    {_, KeyCount} when KeyCount =:= R ->
-        {stop, Reply};
-    {NewReplies, KeyCount} when KeyCount < R ->
+    NewReplies = orddict:update_counter(Reply, 1, Replies),
+    Reduced = fabric_util:remove_ancestors(NewReplies, []),
+    case lists:dropwhile(fun({_, Count}) -> Count < R end, Reduced) of
+    [{QuorumReply, _} | _] ->
+        if length(NewReplies) =:= 1 ->
+            {stop, QuorumReply};
+        true ->
+            % we had some disagreement amongst the workers, so repair is useful
+            {error, needs_repair, QuorumReply}
+        end;
+    [] ->
         if WaitingCount =:= 1 ->
-            % last message arrived, but still no quorum
-            repair_read_quorum_failure(NewReplies);
+            {error, needs_repair};
         true ->
             {ok, {WaitingCount-1, R, NewReplies}}
         end
     end.
 
-skip_message({1, _R, Replies}) ->
-    repair_read_quorum_failure(Replies);
+skip_message({1, _R, _Replies}) ->
+    {error, needs_repair};
 skip_message({WaitingCount, R, Replies}) ->
     {ok, {WaitingCount-1, R, Replies}}.
 
-merge_read_reply(Key, Reply, Replies) ->
-    case lists:keyfind(Key, 1, Replies) of
-    false ->
-        {[{Key, Reply, 1} | Replies], 1};
-    {Key, _, N} ->
-        {lists:keyreplace(Key, 1, Replies, {Key, Reply, N+1}), N+1}
-    end.
 
-make_key({ok, #doc{id=Id, revs=Revs}}) ->
-    {Id, Revs};
-make_key(Else) ->
-    Else.
+open_doc_test() ->
+    Foo1 = {ok, #doc{revs = {1,[<<"foo">>]}}},
+    Foo2 = {ok, #doc{revs = {2,[<<"foo2">>,<<"foo">>]}}},
+    Bar1 = {ok, #doc{revs = {1,[<<"bar">>]}}},
+    Baz1 = {ok, #doc{revs = {1,[<<"baz">>]}}},
+    NF = {not_found, missing},
+    State0 = {3, 2, []},
+    State1 = {2, 2, [{Foo1,1}]},
+    State2 = {1, 2, [{Bar1,1}, {Foo1,1}]},
+    ?assertEqual({ok, State1}, handle_message(Foo1, nil, State0)),
 
-repair_read_quorum_failure(Replies) ->
-    case [Doc || {_Key, {ok, Doc}, _Count} <- Replies] of
-    [] ->
-        {stop, {not_found, missing}};
-    [Doc|_] ->
-        % TODO merge docs to find the winner as determined by replication
-        {stop, {ok, Doc}}
-    end.
\ No newline at end of file
+    % normal case - quorum reached, no disagreement
+    ?assertEqual({stop, Foo1}, handle_message(Foo1, nil, State1)),
+
+    % 2nd worker disagrees, voting continues
+    ?assertEqual({ok, State2}, handle_message(Bar1, nil, State1)),
+
+    % 3rd worker resolves voting, but repair is needed
+    ?assertEqual({error, needs_repair, Foo1}, handle_message(Foo1, nil, State2)),
+
+    % 2nd worker comes up with descendant of Foo1, voting resolved, run repair
+    ?assertEqual({error, needs_repair, Foo2}, handle_message(Foo2, nil, State1)),
+
+    % not_found is considered to be an ancestor of everybody
+    ?assertEqual({error, needs_repair, Foo1}, handle_message(NF, nil, State1)),
+
+    % 3 distinct edit branches result in quorum failure
+    ?assertEqual({error, needs_repair}, handle_message(Baz1, nil, State2)),
+
+    % bad node concludes voting w/o success, run sync repair to get the result
+    ?assertEqual(
+        {error, needs_repair},
+        handle_message({rexi_DOWN, 1, 2, 3}, nil, State2)
+    ).
-- 
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