nickva commented on code in PR #5371:
URL: https://github.com/apache/couchdb/pull/5371#discussion_r1904450157
##########
src/fabric/src/fabric_doc_update.erl:
##########
@@ -292,18 +336,94 @@ 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 == lists:min([W || W <- Workers, W#shard.range ==
Worker#shard.range]).
+
+start_leaders(#acc{} = Acc0) ->
+ #acc{grouped_docs = GroupedDocs} = Acc0,
+ {Workers, _} = lists:unzip(GroupedDocs),
+ Started = 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{started = lists:append([Started, Acc0#acc.started])}.
+
+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{}) ->
+ ok.
+
+append_update_replies([], [], _W, DocReplyDict) ->
DocReplyDict;
-append_update_replies([Doc | Rest], [], Dict0) ->
+append_update_replies([Doc | Rest], [], W, 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)).
-
-skip_message({0, _, W, _, DocReplyDict}) ->
+ append_update_replies(Rest, [], W, dict:append(Doc, noreply, Dict0));
+append_update_replies([Doc | Rest1], [conflict | Rest2], W, Dict0) ->
+ %% fake conflict replies from followers as we won't ask them
+ append_update_replies(
+ Rest1, Rest2, W, dict:append_list(Doc, lists:duplicate(W, conflict),
Dict0)
+ );
+append_update_replies([Doc | Rest1], [Reply | Rest2], W, Dict0) ->
+ append_update_replies(Rest1, Rest2, W, 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;
+ Rest ->
+ [{Worker, Rest} | FoldAcc]
+ end
+ end,
+ [],
+ GroupedDocs0
+ ),
+ Acc1 = Acc0#acc{waiting_count = length(GroupedDocs1), 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], [], Acc0) ->
Review Comment:
Tiny nit: might as well assert Acc0 is an`#acc{}` here as well
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