Buffer rows to reduce number of chunks
This patch reduces the number of chunks in an HTTP chunked response body
by coalescing multiple rows into a single transmission. The default
value is chosen to fill a standard Ethernet frame and can be configured
by setting
[httpd]
chunked_response_buffer = 1490
Setting the buffer size to 0 restores the original behavior of sending
each row in a separate chunk. Note that the same setting is several
streaming responses (e.g. _changes, _all_docs, _views).
COUCHDB-2724
diff --git a/include/couch_mrview.hrl b/include/couch_mrview.hrl
index 1a0cdea..c176839 100644
--- a/include/couch_mrview.hrl
+++ b/include/couch_mrview.hrl
@@ -94,7 +94,10 @@
resp,
prepend,
etag,
- should_close = false
+ should_close = false,
+ buffer = [],
+ bufsize = 0,
+ threshold = 1490
}).
-record(lacc, {
diff --git a/src/couch_mrview_http.erl b/src/couch_mrview_http.erl
index d0da69e..d285240 100644
--- a/src/couch_mrview_http.erl
+++ b/src/couch_mrview_http.erl
@@ -229,7 +229,8 @@
end,
Args = Args1#mrargs{preflight_fun=ETagFun},
{ok, Resp} = couch_httpd:etag_maybe(Req, fun() ->
- VAcc0 = #vacc{db=Db, req=Req},
+ Max = chttpd:chunked_response_buffer_size(),
+ VAcc0 = #vacc{db=Db, req=Req, threshold=Max},
DbName = ?b2l(Db#db.name),
UsersDbName = config:get("couch_httpd_auth",
"authentication_db",
@@ -274,7 +275,8 @@
end,
Args = Args0#mrargs{preflight_fun=ETagFun},
{ok, Resp} = couch_httpd:etag_maybe(Req, fun() ->
- VAcc0 = #vacc{db=Db, req=Req},
+ Max = chttpd:chunked_response_buffer_size(),
+ VAcc0 = #vacc{db=Db, req=Req, threshold=Max},
couch_mrview:query_view(Db, DDoc, ViewName, Args, fun view_cb/2, VAcc0)
end),
case is_record(Resp, vacc) of
@@ -291,7 +293,8 @@
couch_mrview_util:validate_args(QueryArg)
end, Queries),
{ok, Resp2} = couch_httpd:etag_maybe(Req, fun() ->
- VAcc0 = #vacc{db=Db, req=Req, prepend="\r\n"},
+ Max = chttpd:chunked_response_buffer_size(),
+ VAcc0 = #vacc{db=Db, req=Req, prepend="\r\n", threshold=Max},
%% TODO: proper calculation of etag
Etag = couch_uuids:new(),
Headers = [{"ETag", Etag}],
@@ -331,7 +334,7 @@
Headers = [{"ETag", Acc#vacc.etag}],
{ok, Resp} = chttpd:start_delayed_json_response(Acc#vacc.req, 200, Headers),
view_cb({meta, Meta}, Acc#vacc{resp=Resp, should_close=true});
-view_cb({meta, Meta}, #vacc{resp=Resp}=Acc) ->
+view_cb({meta, Meta}, #vacc{}=Acc) ->
% Sending metadata
Parts = case couch_util:get_value(total, Meta) of
undefined -> [];
@@ -344,26 +347,25 @@
UpdateSeq -> [io_lib:format("\"update_seq\":~p", [UpdateSeq])]
end ++ ["\"rows\":["],
Chunk = [prepend_val(Acc), "{", string:join(Parts, ","), "\r\n"],
- {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Chunk),
- {ok, Acc#vacc{resp=Resp1, prepend=""}};
+ {ok, AccOut} = maybe_flush_response(Acc, Chunk, iolist_size(Chunk)),
+ {ok, AccOut#vacc{prepend=""}};
view_cb({row, Row}, Acc) ->
% Adding another row
Chunk = [prepend_val(Acc), row_to_json(Row)],
- {ok, Resp1} = chttpd:send_delayed_chunk(Acc#vacc.resp, Chunk),
- {ok, Acc#vacc{prepend=",\r\n", resp=Resp1}};
+ maybe_flush_response(Acc, Chunk, iolist_size(Chunk));
view_cb(complete, #vacc{resp=undefined}=Acc) ->
% Nothing in view
{ok, Resp} = chttpd:send_json(Acc#vacc.req, 200, {[{rows, []}]}),
{ok, Acc#vacc{resp=Resp}};
-view_cb(complete, #vacc{resp=Resp}=Acc) ->
+view_cb(complete, #vacc{resp=Resp, buffer=Buf, threshold=Max}=Acc) ->
% Finish view output and possibly end the response
- {ok, Resp1} = chttpd:send_delayed_chunk(Resp, "\r\n]}"),
+ {ok, Resp1} = chttpd:close_delayed_json_object(Resp, Buf, "\r\n]}", Max),
case Acc#vacc.should_close of
true ->
{ok, Resp2} = chttpd:end_delayed_json_response(Resp1),
{ok, Acc#vacc{resp=Resp2}};
_ ->
- {ok, Acc#vacc{resp=Resp1, prepend=",\r\n"}}
+ {ok, Acc#vacc{resp=Resp1, prepend=",\r\n", buffer=[], bufsize=0}}
end;
view_cb({error, Reason}, #vacc{resp=undefined}=Acc) ->
{ok, Resp} = chttpd:send_error(Acc#vacc.req, Reason),
@@ -372,6 +374,19 @@
{ok, Resp1} = chttpd:send_delayed_error(Resp, Reason),
{ok, Acc#vacc{resp=Resp1}}.
+maybe_flush_response(#vacc{bufsize=Size, threshold=Max} = Acc, Data, Len)
+ when Size > 0 andalso (Size + Len) > Max ->
+ #vacc{buffer = Buffer, resp = Resp} = Acc,
+ {ok, R1} = chttpd:send_delayed_chunk(Resp, Buffer),
+ {ok, Acc#vacc{prepend = ",\r\n", buffer = Data, bufsize = Len, resp = R1}};
+maybe_flush_response(Acc0, Data, Len) ->
+ #vacc{buffer = Buf, bufsize = Size} = Acc0,
+ Acc = Acc0#vacc{
+ prepend = ",\r\n",
+ buffer = [Buf | Data],
+ bufsize = Size + Len
+ },
+ {ok, Acc}.
prepend_val(#vacc{prepend=Prepend}) ->
case Prepend of
