jadeallenx

Intro

Last Friday (May 29, 2015) I published a tweet teaser about @macintux and my work on Lager 3.x. We have been benchmarking the "final" product including all of the community PRs we have decided to merge for 3.0 and we achieved some really great results over the 2.x branch. Those graphs look like this:

https://www.dropbox.com/s/417ysstatybvtkd/log_1000.png https://www.dropbox.com/s/iwoz7r2s690itdr/tput_1000.png

Many had questions about how we achieved such a big improvement in throughput and latency. The secret is very simple.

1. We tried to move some decisions about whether to do work earlier into the process.
2. We moved a couple pieces of global state into ets.

jadeallenx

handoff_starting(_TargetNode, State) ->
    {true, State}.

handoff_cancelled(State) ->
    {ok, State}.

handoff_finished(_TargetNode, State) ->
    {ok, State}.

jadeallenx

is_empty(State) ->
    Result = case list_dir(State) of
        [] -> true; 
        {error, _Reason} -> true;
        _ -> false
    end,
    {Result, State}.

jadeallenx

handle_handoff_data(Data, State) ->
    {Meta, Blob} = binary_to_term(Data),
    R = case Meta#file.csum =:= erlang:adler32(Blob) of
        true ->
            Result = store(State, Meta, Blob),
            ?PRINT(Result),
            ok;
        false ->
            {error, file_checksum_differs}
    end,

jadeallenx

encode_handoff_item(_Key, Data = {_Meta, _File}) ->
    term_to_binary(Data).

jadeallenx

handle_handoff_command(?FOLD_REQ{foldfun=VisitFun, acc0=Acc0}, _Sender, State) ->
    AllObjects = get_all_objects(State),
    Base = make_base_path(State),

    Do = fun(Object, AccIn) ->
                 MPath = path_from_object(Base, Object, ".meta"),
                 ?PRINT(MPath),
                 Meta = get_metadata(MPath),
                 ?PRINT(Meta),
                 %% TODO: Get all file versions

jadeallenx

-record(riak_core_fold_req_v2, {
          foldfun :: fun(),
          acc0 :: term(),
          forwardable :: boolean(),
          opts = [] :: list()}).
          
-define(FOLD_REQ, #riak_core_fold_req_v2).

jadeallenx

handle_handoff_command(?FOLD_REQ{foldfun=VisitFun, acc0=Acc0}, _Sender, State) ->
    %% eliding details for now. Don't worry, we'll get to them shortly.
    Final = lists:foldl(fun magic/2, Acc0, object_list()),
    {reply, Final, State}.

jadeallenx

handle_handoff_command(_Message, _Sender, State) ->
    {noreply, State}.

handoff_starting(_TargetNode, State) ->
    {true, State}.

handoff_cancelled(State) ->
    {ok, State}.

handoff_finished(_TargetNode, State) ->

jadeallenx

ping() ->
    DocIdx = riak_core_util:chash_key({<<"ping">>, term_to_binary(now())}),
    PrefList = riak_core_apl:get_primary_apl(DocIdx, 1, demoapp),
    [{IndexNode, _Type}] = PrefList,
    riak_core_vnode_master:sync_spawn_command(IndexNode, ping, demoapp_vnode_master).