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
Note that the same setting is several other streaming responses (e.g.
_changes, _all_docs, _views).
COUCHDB-2724
diff --git a/src/mango_httpd.erl b/src/mango_httpd.erl
index 54510fb..566ff09 100644
--- a/src/mango_httpd.erl
+++ b/src/mango_httpd.erl
@@ -25,7 +25,10 @@
-record(vacc, {
resp,
prepend,
- kvs
+ kvs,
+ buffer = [],
+ bufsize = 0,
+ threshold = 1490
}).
handle_req(#httpd{} = Req, Db0) ->
@@ -218,13 +221,14 @@
chttpd:start_delayed_json_response(Req, 200, [], "{\"docs\":[").
-end_find_resp(Acc) ->
- #vacc{resp=Resp0, kvs=KVs} = Acc,
+end_find_resp(Acc0) ->
+ #vacc{resp=Resp00, buffer=Buf, kvs=KVs, threshold=Max} = Acc0,
+ {ok, Resp0} = chttpd:close_delayed_json_object(Resp00, Buf, "\r\n]}", Max),
FinalAcc = lists:foldl(fun({K, V}, Acc) ->
JK = ?JSON_ENCODE(K),
JV = ?JSON_ENCODE(V),
[JV, ": ", JK, ",\r\n" | Acc]
- end, ["\r\n]"], KVs),
+ end, [], KVs),
Chunk = lists:reverse(FinalAcc, ["}\r\n"]),
{ok, Resp1} = chttpd:send_delayed_chunk(Resp0, Chunk),
chttpd:end_delayed_json_response(Resp1).
@@ -234,20 +238,34 @@
Acc0 = #vacc{
resp = Resp,
prepend = "\r\n",
- kvs = []
+ kvs = [],
+ threshold = chttpd:chunked_response_buffer_size()
},
mango_crud:find(Db, Sel, fun handle_doc/2, Acc0, Opts).
handle_doc({add_key, Key, Value}, Acc0) ->
- #vacc{resp=Resp, prepend=Prepend, kvs=KVs} = Acc0,
+ #vacc{kvs=KVs} = Acc0,
NewKVs = lists:keystore(Key, 1, KVs, {Key, Value}),
- {ok, {Resp, Prepend, NewKVs}};
+ {ok, Acc0#vacc{kvs = NewKVs}};
handle_doc({row, Doc}, Acc0) ->
- #vacc{resp=Resp0, prepend=Prepend, kvs=KVs} = Acc0,
+ #vacc{prepend=Prepend} = Acc0,
Chunk = [Prepend, ?JSON_ENCODE(Doc)],
- {ok, Resp1} = chttpd:send_delayed_chunk(Resp0, Chunk),
- {ok, {Resp1, ",\r\n", KVs}}.
+ maybe_flush_response(Acc0, Chunk, iolist_size(Chunk)).
+
+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}.
parse_index_param("limit", Value) ->
