Github user eiri commented on a diff in the pull request:
https://github.com/apache/couchdb-fabric/pull/61#discussion_r70139806
--- Diff: src/fabric_group_info.erl ---
@@ -58,17 +58,23 @@ handle_message({rexi_EXIT, Reason}, Shard, {Counters,
Acc, Ushards}) ->
end;
handle_message({ok, Info}, Shard, {Counters0, Acc, Ushards}) ->
- NewAcc = append_result(Info, Shard, Acc, Ushards),
- Counters1 = fabric_dict:store(Shard, ok, Counters0),
- Counters = fabric_view:remove_overlapping_shards(Shard, Counters1),
- case is_complete(Counters) of
- false ->
- {ok, {Counters, NewAcc, Ushards}};
- true ->
- Pending = aggregate_pending(NewAcc),
- Infos = get_infos(NewAcc),
- Results = [{updates_pending, {Pending}} | merge_results(Infos)],
- {stop, Results}
+ case fabric_dict:lookup_element(Shard, Counters0) of
+ undefined ->
+ % already heard from other node in this range
--- End diff --
It can for the shards we haven't received a response yet.
It goes like this - we are initiating `Counters` dict with all the shards
as keys and values as `nil`. Shard is a combination of range and node, so even
though they are all unique, ranges (and accordingly their view_info) are not.
We are doing this because we can't guess which node with a given range will
respond first or respond at all.
Now, once we are starting to receive responses, we are updating our
`Counters0` dict with `ok` for the received range+node, with gives as
`Counters1`, and then removing all the duplicated ranges for the rest of the
nodes, which gives as `Counters`.
Once our `Counters` dict doesn't have any `nil` left (`is_complete/1` is a
check for that) we know that we've received the responses for all the ranges
and aggregating info we've kept on `NewAcc ` into final response.
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