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Reduce intra cluster conflicts #5371

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186 changes: 142 additions & 44 deletions src/fabric/src/fabric_doc_update.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,10 @@
doc_count,
w,
grouped_docs,
reply
reply,
update_options,
leaders = [],
started = []
}).

go(_, [], _) ->
Expand All @@ -33,25 +36,25 @@ go(DbName, AllDocs0, Opts) ->
validate_atomic_update(DbName, AllDocs, lists:member(all_or_nothing, Opts)),
Options = lists:delete(all_or_nothing, Opts),
GroupedDocs = lists:map(
fun({#shard{name = Name, node = Node} = Shard, Docs}) ->
Docs1 = untag_docs(Docs),
Ref = rexi:cast(Node, {fabric_rpc, update_docs, [Name, Docs1, Options]}),
{Shard#shard{ref = Ref}, Docs}
fun({#shard{} = Shard, Docs}) ->
{Shard#shard{ref = make_ref()}, Docs}
end,
group_docs_by_shard(DbName, AllDocs)
),
{Workers, _} = lists:unzip(GroupedDocs),
RexiMon = fabric_util:create_monitors(Workers),
W = couch_util:get_value(w, Options, integer_to_list(mem3:quorum(DbName))),
Acc0 = #acc{
update_options = Options,
waiting_count = length(Workers),
doc_count = length(AllDocs),
w = list_to_integer(W),
grouped_docs = GroupedDocs,
reply = dict:new()
},
Timeout = fabric_util:request_timeout(),
try rexi_utils:recv(Workers, #shard.ref, fun handle_message/3, Acc0, infinity, Timeout) of
Acc1 = start_leaders(Acc0),
try rexi_utils:recv(Workers, #shard.ref, fun handle_message/3, Acc1, infinity, Timeout) of
{ok, {Health, Results}} when
Health =:= ok; Health =:= accepted; Health =:= error
->
Expand All @@ -72,61 +75,78 @@ go(DbName, AllDocs0, Opts) ->
rexi_monitor:stop(RexiMon)
end.

handle_message({rexi_DOWN, _, {_, NodeRef}, _}, _Worker, #acc{} = Acc0) ->
handle_message({rexi_DOWN, _, {_, NodeRef}, _}, Worker, #acc{} = Acc0) ->
#acc{grouped_docs = GroupedDocs} = Acc0,
NewGrpDocs = [X || {#shard{node = N}, _} = X <- GroupedDocs, N =/= NodeRef],
skip_message(Acc0#acc{waiting_count = length(NewGrpDocs), grouped_docs = NewGrpDocs});
Acc1 = Acc0#acc{waiting_count = length(NewGrpDocs), grouped_docs = NewGrpDocs},
Acc2 = start_followers(Worker, Acc1),
skip_message(Acc2);
handle_message({rexi_EXIT, _}, Worker, #acc{} = Acc0) ->
#acc{waiting_count = WC, grouped_docs = GrpDocs} = Acc0,
NewGrpDocs = lists:keydelete(Worker, 1, GrpDocs),
skip_message(Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs});
Acc1 = Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs},
Acc2 = start_followers(Worker, Acc1),
skip_message(Acc2);
handle_message({error, all_dbs_active}, Worker, #acc{} = Acc0) ->
% treat it like rexi_EXIT, the hope at least one copy will return successfully
#acc{waiting_count = WC, grouped_docs = GrpDocs} = Acc0,
NewGrpDocs = lists:keydelete(Worker, 1, GrpDocs),
skip_message(Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs});
Acc1 = Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs},
Acc2 = start_followers(Worker, Acc1),
skip_message(Acc2);
handle_message(internal_server_error, Worker, #acc{} = Acc0) ->
% happens when we fail to load validation functions in an RPC worker
#acc{waiting_count = WC, grouped_docs = GrpDocs} = Acc0,
NewGrpDocs = lists:keydelete(Worker, 1, GrpDocs),
skip_message(Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs});
Acc1 = Acc0#acc{waiting_count = WC - 1, grouped_docs = NewGrpDocs},
Acc2 = start_followers(Worker, Acc1),
skip_message(Acc2);
handle_message(attachment_chunk_received, _Worker, #acc{} = Acc0) ->
{ok, Acc0};
handle_message({ok, Replies}, Worker, #acc{} = Acc0) ->
#acc{
waiting_count = WaitingCount,
doc_count = DocCount,
w = W,
grouped_docs = GroupedDocs,
reply = DocReplyDict0
} = Acc0,
{value, {_, Docs}, NewGrpDocs} = lists:keytake(Worker, 1, GroupedDocs),
DocReplyDict = append_update_replies(Docs, Replies, DocReplyDict0),
case {WaitingCount, dict:size(DocReplyDict)} of
{1, _} ->
% last message has arrived, we need to conclude things
{Health, W, Reply} = dict:fold(
fun force_reply/3,
{ok, W, []},
DocReplyDict
),
{stop, {Health, Reply}};
{_, DocCount} ->
% we've got at least one reply for each document, let's take a look
case dict:fold(fun maybe_reply/3, {stop, W, []}, DocReplyDict) of
continue ->
{ok, Acc0#acc{
waiting_count = WaitingCount - 1,
grouped_docs = NewGrpDocs,
reply = DocReplyDict
}};
{stop, W, FinalReplies} ->
{stop, {ok, FinalReplies}}
end;
_ ->
{ok, Acc0#acc{
waiting_count = WaitingCount - 1, grouped_docs = NewGrpDocs, reply = DocReplyDict
}}
{value, {_, Docs}, NewGrpDocs0} = lists:keytake(Worker, 1, GroupedDocs),
IsLeader = lists:member(Worker#shard.ref, Acc0#acc.leaders),
DocReplyDict = append_update_replies(Docs, Replies, W, IsLeader, DocReplyDict0),
Acc1 = Acc0#acc{grouped_docs = NewGrpDocs0, reply = DocReplyDict},
Acc2 = remove_conflicts(Docs, Replies, Acc1),
NewGrpDocs = Acc2#acc.grouped_docs,
case skip_message(Acc2) of
{stop, Msg} ->
{stop, Msg};
{ok, Acc3} ->
Acc4 = start_followers(Worker, Acc3),
case {Acc4#acc.waiting_count, dict:size(DocReplyDict)} of
{1, _} ->
% last message has arrived, we need to conclude things
{Health, W, Reply} = dict:fold(
fun force_reply/3,
{ok, W, []},
DocReplyDict
),
{stop, {Health, Reply}};
{_, DocCount} ->
% we've got at least one reply for each document, let's take a look
case dict:fold(fun maybe_reply/3, {stop, W, []}, DocReplyDict) of
continue ->
{ok, Acc4#acc{
waiting_count = Acc4#acc.waiting_count - 1,
grouped_docs = NewGrpDocs
}};
{stop, W, FinalReplies} ->
{stop, {ok, FinalReplies}}
end;
_ ->
{ok, Acc4#acc{
waiting_count = Acc4#acc.waiting_count - 1,
grouped_docs = NewGrpDocs
}}
end
end;
handle_message({missing_stub, Stub}, _, _) ->
throw({missing_stub, Stub});
Expand Down Expand Up @@ -318,13 +338,91 @@ group_docs_by_shard(DbName, Docs) ->
)
).

append_update_replies([], [], DocReplyDict) ->
%% use 'lowest' node that hosts this shard range as leader
is_leader(Worker, Workers) ->
Worker#shard.node ==
lists:min([W#shard.node || W <- Workers, W#shard.range == Worker#shard.range]).

start_leaders(#acc{} = Acc0) ->
#acc{grouped_docs = GroupedDocs} = Acc0,
{Workers, _} = lists:unzip(GroupedDocs),
LeaderRefs = lists:foldl(
fun({Worker, Docs}, RefAcc) ->
case is_leader(Worker, Workers) of
true ->
start_worker(Worker, Docs, Acc0),
[Worker#shard.ref | RefAcc];
false ->
RefAcc
end
end,
[],
GroupedDocs
),
Acc0#acc{leaders = LeaderRefs, started = LeaderRefs}.

start_followers(#shard{} = Leader, #acc{} = Acc0) ->
Followers = [
{Worker, Docs}
|| {Worker, Docs} <- Acc0#acc.grouped_docs,
Worker#shard.range == Leader#shard.range,
not lists:member(Worker#shard.ref, Acc0#acc.started)
],
lists:foreach(
fun({Worker, Docs}) ->
start_worker(Worker, Docs, Acc0)
end,
Followers
),
Started = [Ref || {#shard{ref = Ref}, _Docs} <- Followers],
Acc0#acc{started = lists:append([Started, Acc0#acc.started])}.

start_worker(#shard{ref = Ref} = Worker, Docs, #acc{} = Acc0) when is_reference(Ref) ->
#shard{name = Name, node = Node} = Worker,
#acc{update_options = UpdateOptions} = Acc0,
rexi:cast_ref(Ref, Node, {fabric_rpc, update_docs, [Name, untag_docs(Docs), UpdateOptions]}),
ok;
start_worker(#shard{ref = undefined}, _Docs, #acc{}) ->
% for unit tests below.
ok.

append_update_replies([], [], _W, _IsLeader, DocReplyDict) ->
DocReplyDict;
append_update_replies([Doc | Rest], [], Dict0) ->
append_update_replies([Doc | Rest], [], W, IsLeader, Dict0) ->
% icky, if replicated_changes only errors show up in result
append_update_replies(Rest, [], dict:append(Doc, noreply, Dict0));
append_update_replies([Doc | Rest1], [Reply | Rest2], Dict0) ->
append_update_replies(Rest1, Rest2, dict:append(Doc, Reply, Dict0)).
append_update_replies(Rest, [], W, IsLeader, dict:append(Doc, noreply, Dict0));
append_update_replies([Doc | Rest1], [conflict | Rest2], W, true, Dict0) ->
%% fake conflict replies from followers as we won't ask them
append_update_replies(
Rest1, Rest2, W, true, dict:append_list(Doc, lists:duplicate(W, conflict), Dict0)
);
append_update_replies([Doc | Rest1], [Reply | Rest2], W, IsLeader, Dict0) ->
append_update_replies(Rest1, Rest2, W, IsLeader, dict:append(Doc, Reply, Dict0)).

%% leader found a conflict, remove that doc from the other (follower) workers,
%% removing the worker entirely if no docs remain.
remove_conflicts([], [], #acc{} = Acc0) ->
Acc0;
remove_conflicts([Doc | DocRest], [conflict | ReplyRest], #acc{} = Acc0) ->
#acc{grouped_docs = GroupedDocs0} = Acc0,
GroupedDocs1 = lists:foldl(
fun({Worker, Docs}, FoldAcc) ->
case lists:delete(Doc, Docs) of
[] ->
FoldAcc#acc{waiting_count = FoldAcc#acc.waiting_count - 1};
Rest ->
[{Worker, Rest} | FoldAcc]
end
end,
[],
GroupedDocs0
),
Acc1 = Acc0#acc{grouped_docs = GroupedDocs1},
remove_conflicts(DocRest, ReplyRest, Acc1);
remove_conflicts([_Doc | DocRest], [_Reply | ReplyRest], #acc{} = Acc0) ->
remove_conflicts(DocRest, ReplyRest, Acc0);
remove_conflicts([_Doc | DocRest], [], #acc{} = Acc0) ->
remove_conflicts(DocRest, [], Acc0).

skip_message(#acc{waiting_count = 0, w = W, reply = DocReplyDict}) ->
{Health, W, Reply} = dict:fold(fun force_reply/3, {ok, W, []}, DocReplyDict),
Expand Down