Add option to delay responses until the end

rel/overlay/etc/default.ini

@@ -130,6 +130,9 @@ prefer_minimal = Cache-Control, Content-Length, Content-Range, Content-Type, ETa
 ; _dbs_info in a request
 max_db_number_for_dbs_info_req = 100
 
+; set to true to delay the start of a response until the end has been calculated
+;buffer_response = false
+
 ; authentication handlers
 ; authentication_handlers = {chttpd_auth, cookie_authentication_handler}, {chttpd_auth, default_authentication_handler}
 ; uncomment the next line to enable proxy authentication

src/chttpd/src/chttpd.erl

@@ -52,8 +52,9 @@
     req,
     code,
     headers,
-    first_chunk,
-    resp=nil
+    chunks,
+    resp=nil,
+    buffer_response=false
 }).
 
 start_link() ->
@@ -780,40 +781,54 @@ start_json_response(Req, Code, Headers0) ->
 end_json_response(Resp) ->
     couch_httpd:end_json_response(Resp).
 
+
 start_delayed_json_response(Req, Code) ->
     start_delayed_json_response(Req, Code, []).
 
+
 start_delayed_json_response(Req, Code, Headers) ->
     start_delayed_json_response(Req, Code, Headers, "").
 
+
 start_delayed_json_response(Req, Code, Headers, FirstChunk) ->
     {ok, #delayed_resp{
         start_fun = fun start_json_response/3,
         req = Req,
         code = Code,
         headers = Headers,
-        first_chunk = FirstChunk}}.
+        chunks = [FirstChunk],
+        buffer_response = buffer_response(Req)}}.
+
 
 start_delayed_chunked_response(Req, Code, Headers) ->
     start_delayed_chunked_response(Req, Code, Headers, "").
 
+
 start_delayed_chunked_response(Req, Code, Headers, FirstChunk) ->
     {ok, #delayed_resp{
         start_fun = fun start_chunked_response/3,
         req = Req,
         code = Code,
         headers = Headers,
-        first_chunk = FirstChunk}}.
+        chunks = [FirstChunk],
+        buffer_response = buffer_response(Req)}}.
+
 
-send_delayed_chunk(#delayed_resp{}=DelayedResp, Chunk) ->
+send_delayed_chunk(#delayed_resp{buffer_response=false}=DelayedResp, Chunk) ->
     {ok, #delayed_resp{resp=Resp}=DelayedResp1} =
         start_delayed_response(DelayedResp),
     {ok, Resp} = send_chunk(Resp, Chunk),
-    {ok, DelayedResp1}.
+    {ok, DelayedResp1};
+
+send_delayed_chunk(#delayed_resp{buffer_response=true}=DelayedResp, Chunk) ->
+    #delayed_resp{chunks = Chunks} = DelayedResp,
+    {ok, DelayedResp#delayed_resp{chunks = [Chunk | Chunks]}}.
+
 
 send_delayed_last_chunk(Req) ->
     send_delayed_chunk(Req, []).
 
+
 send_delayed_error(#delayed_resp{req=Req,resp=nil}=DelayedResp, Reason) ->
     {Code, ErrorStr, ReasonStr} = error_info(Reason),
     {ok, Resp} = send_error(Req, Code, ErrorStr, ReasonStr),
@@ -823,6 +838,7 @@ send_delayed_error(#delayed_resp{resp=Resp, req=Req}, Reason) ->
     log_error_with_stack_trace(Reason),
     throw({http_abort, Resp, Reason}).
 
+
 close_delayed_json_object(Resp, Buffer, Terminator, 0) ->
     % Use a separate chunk to close the streamed array to maintain strict
     % compatibility with earlier versions. See COUCHDB-2724
@@ -831,10 +847,22 @@ close_delayed_json_object(Resp, Buffer, Terminator, 0) ->
 close_delayed_json_object(Resp, Buffer, Terminator, _Threshold) ->
     send_delayed_chunk(Resp, [Buffer | Terminator]).
 
-end_delayed_json_response(#delayed_resp{}=DelayedResp) ->
+
+end_delayed_json_response(#delayed_resp{buffer_response=false}=DelayedResp) ->
     {ok, #delayed_resp{resp=Resp}} =
         start_delayed_response(DelayedResp),
-    end_json_response(Resp).
+    end_json_response(Resp);
+
+end_delayed_json_response(#delayed_resp{buffer_response=true}=DelayedResp) ->
+    #delayed_resp{
+        req = Req,
+        code = Code,
+        headers = Headers,
+        chunks = Chunks
+    } = DelayedResp,
+    {ok, Resp} = start_response_length(Req, Code, Headers, iolist_size(Chunks)),
+    send(Resp, lists:reverse(Chunks)).
+
 
 get_delayed_req(#delayed_resp{req=#httpd{mochi_req=MochiReq}}) ->
     MochiReq;
@@ -847,7 +875,7 @@ start_delayed_response(#delayed_resp{resp=nil}=DelayedResp) ->
         req=Req,
         code=Code,
         headers=Headers,
-        first_chunk=FirstChunk
+        chunks=[FirstChunk]
     }=DelayedResp,
     {ok, Resp} = StartFun(Req, Code, Headers),
     case FirstChunk of
@@ -858,6 +886,18 @@ start_delayed_response(#delayed_resp{resp=nil}=DelayedResp) ->
 start_delayed_response(#delayed_resp{}=DelayedResp) ->
     {ok, DelayedResp}.
 
+
+buffer_response(Req) ->
+    case chttpd:qs_value(Req, "buffer_response") of
+        "false" ->
+            false;
+        "true" ->
+            true;
+        _ ->
+            config:get_boolean("chttpd", "buffer_response", false)
+    end.
+
+
 error_info({Error, Reason}) when is_list(Reason) ->
     error_info({Error, couch_util:to_binary(Reason)});
 error_info(bad_request) ->

src/chttpd/test/eunit/chttpd_delayed_test.erl

@@ -0,0 +1,73 @@
+-module(chttpd_delayed_test).
+
+-include_lib("couch/include/couch_eunit.hrl").
+-include_lib("couch/include/couch_db.hrl").
+
+-define(USER, "chttpd_view_test_admin").
+-define(PASS, "pass").
+-define(AUTH, {basic_auth, {?USER, ?PASS}}).
+-define(CONTENT_JSON, {"Content-Type", "application/json"}).
+-define(DDOC, "{\"_id\": \"_design/bar\", \"views\": {\"baz\":
+               {\"map\": \"function(doc) {emit(doc._id, doc._id);}\"}}}").
+
+-define(FIXTURE_TXT, ?ABS_PATH(?FILE)).
+-define(i2l(I), integer_to_list(I)).
+-define(TIMEOUT, 60). % seconds
+
+setup() ->
+    Hashed = couch_passwords:hash_admin_password(?PASS),
+    ok = config:set("admins", ?USER, ?b2l(Hashed), _Persist=false),
+    ok = config:set("chttpd", "buffer_response", "true"),
+    TmpDb = ?tempdb(),
+    Addr = config:get("chttpd", "bind_address", "127.0.0.1"),
+    Port = mochiweb_socket_server:get(chttpd, port),
+    Url = lists:concat(["http://", Addr, ":", Port, "/", ?b2l(TmpDb)]),
+    create_db(Url),
+    Url.
+
+teardown(Url) ->
+    delete_db(Url),
+    ok = config:delete("admins", ?USER, _Persist=false).
+
+create_db(Url) ->
+    {ok, Status, _, _} = test_request:put(Url, [?CONTENT_JSON, ?AUTH], "{}"),
+    ?assert(Status =:= 201 orelse Status =:= 202).
+
+
+delete_db(Url) ->
+    {ok, 200, _, _} = test_request:delete(Url, [?AUTH]).
+
+
+all_test_() ->
+    {
+        "chttpd delay tests",
+        {
+            setup,
+            fun chttpd_test_util:start_couch/0, fun chttpd_test_util:stop_couch/1,
+            {
+                foreach,
+                fun setup/0, fun teardown/1,
+                [
+                    fun test_buffer_response_all_docs/1,
+                    fun test_buffer_response_changes/1
+                ]
+            }
+        }
+    }.
+
+
+test_buffer_response_all_docs(Url) ->
+    assert_has_content_length(Url ++ "/_all_docs").
+
+
+test_buffer_response_changes(Url) ->
+    assert_has_content_length(Url ++ "/_changes").
+
+
+assert_has_content_length(Url) ->
+    {timeout, ?TIMEOUT, ?_test(begin
+        {ok, Code, Headers, _Body} = test_request:get(Url, [?AUTH]),
+        ?assertEqual(200, Code),
+        ?assert(lists:keymember("Content-Length", 1, Headers))
+    end)}.
+