HTTPDecoder: don't deliver unsolicited responses

[weissi]

Motivation:

Despite the fact that we already stopped delivering unsolicited
responses for the HTTP response decoder, there was a window where we
would deliver a second .head for a response that come without a request.

Modifications:

Don't deliver a second .head even if send together with a first, legit
response.

Result:

Being a HTTP client using NIO is now easier.

[weissi]

@swift-nio-bot test perf please

[weissi]

@swift-nio-bot test perf please

[swift-nio-bot]

performance report

build id: 11

timestamp: Tue Aug 6 14:57:10 UTC 2019

results

name	min	max	mean	std
write_http_headers	0.004672050476074219	0.004701972007751465	0.004682493209838867	8.639215274420695e-06
bytebuffer_write_12MB_short_string_literals	0.4871819019317627	0.4940100908279419	0.48902039527893065	0.0018799653005042425
bytebuffer_write_12MB_short_calculated_strings	0.49014902114868164	0.4918309450149536	0.49094557762145996	0.0004974480861775824
bytebuffer_write_12MB_medium_string_literals	0.18102598190307617	0.18423199653625488	0.18161729574203492	0.0009781288441399914
bytebuffer_write_12MB_medium_calculated_strings	0.23320090770721436	0.23453402519226074	0.23363288640975952	0.00036782887387042654
bytebuffer_write_12MB_large_calculated_strings	0.21282804012298584	0.21382200717926025	0.21327890157699586	0.0002855270641293843
bytebuffer_lots_of_rw	0.5475389957427979	0.555306077003479	0.5494376063346863	0.002277967902230494
bytebuffer_write_http_response_ascii_only_as_string	0.039848923683166504	0.04050302505493164	0.04005320072174072	0.00023919532793854672
bytebuffer_write_http_response_ascii_only_as_staticstring	0.029270052909851074	0.029846906661987305	0.029430699348449708	0.00022141405569751815
bytebuffer_write_http_response_some_nonascii_as_string	0.03985905647277832	0.040418028831481934	0.039982497692108154	0.00022256794173638935
bytebuffer_write_http_response_some_nonascii_as_staticstring	0.029218077659606934	0.029819965362548828	0.029368603229522706	0.0002376952062195706
no-net_http1_10k_reqs_1_conn	0.14649200439453125	0.1478569507598877	0.1471501111984253	0.0003900635924291901
http1_10k_reqs_1_conn	0.5829799175262451	0.586804986000061	0.5848252892494201	0.0013004454023887095
http1_10k_reqs_100_conns	0.5819300413131714	0.5867229700088501	0.5844359993934631	0.0015633035310051201
future_whenallsucceed_100k_immediately_succeeded_off_loop	0.1235039234161377	0.12495195865631104	0.12418497800827026	0.0004439429397698077
future_whenallsucceed_100k_immediately_succeeded_on_loop	0.12438499927520752	0.13578295707702637	0.12640070915222168	0.0033940595117112485
future_whenallsucceed_100k_deferred_off_loop	0.6110810041427612	0.6168539524078369	0.613690710067749	0.0017875830012681166
future_whenallsucceed_100k_deferred_on_loop	0.19170498847961426	0.19366800785064697	0.19259120225906373	0.000623231330295191
future_whenallcomplete_100k_immediately_succeeded_off_loop	0.10088801383972168	0.10258305072784424	0.10164060592651367	0.0007104215193182487
future_whenallcomplete_100k_immediately_succeeded_on_loop	0.10087597370147705	0.10293400287628174	0.10171210765838623	0.0007397542620493532
future_whenallcomplete_100k_deferred_off_loop	0.5878069400787354	0.6022310256958008	0.5959251046180725	0.004098161695396617
future_whenallcomplete_100k_deferred_on_loop	0.17399001121520996	0.18085205554962158	0.1757832169532776	0.0019693970897714224
future_reduce_10k_futures	0.04932093620300293	0.050221920013427734	0.04979032278060913	0.00023765166603867302
future_reduce_into_10k_futures	0.05013096332550049	0.05124092102050781	0.05061229467391968	0.00036136780359037694
channel_pipeline_1m_events	0.2188739776611328	0.21908092498779297	0.21894439458847045	7.563163309064769e-05

comparison

name	current	previous	winner	diff
write_http_headers	0.004682493209838867	0.0047024011611938475	previous	0%
bytebuffer_write_12MB_short_string_literals	0.48902039527893065	0.4893687844276428	current	0%
bytebuffer_write_12MB_short_calculated_strings	0.49094557762145996	0.49095200300216674	previous	0%
bytebuffer_write_12MB_medium_string_literals	0.18161729574203492	0.18113089799880983	previous	0%
bytebuffer_write_12MB_medium_calculated_strings	0.23363288640975952	0.2331204056739807	previous	0%
bytebuffer_write_12MB_large_calculated_strings	0.21327890157699586	0.2108012080192566	previous	1%
bytebuffer_lots_of_rw	0.5494376063346863	0.6138427138328553	current	-10%
bytebuffer_write_http_response_ascii_only_as_string	0.04005320072174072	0.04070550203323364	current	-1%
bytebuffer_write_http_response_ascii_only_as_staticstring	0.029430699348449708	0.029402494430541992	current	0%
bytebuffer_write_http_response_some_nonascii_as_string	0.039982497692108154	0.04065009355545044	current	-1%
bytebuffer_write_http_response_some_nonascii_as_staticstring	0.029368603229522706	0.02929360866546631	previous	0%
no-net_http1_10k_reqs_1_conn	0.1471501111984253	0.1512933850288391	current	-2%
http1_10k_reqs_1_conn	0.5848252892494201	0.587480092048645	previous	0%
http1_10k_reqs_100_conns	0.5844359993934631	0.5857821941375733	current	0%
future_whenallsucceed_100k_immediately_succeeded_off_loop	0.12418497800827026	0.1207085132598877	previous	3%
future_whenallsucceed_100k_immediately_succeeded_on_loop	0.12640070915222168	0.12248148918151855	previous	3%
future_whenallsucceed_100k_deferred_off_loop	0.613690710067749	0.6143378973007202	previous	0%
future_whenallsucceed_100k_deferred_on_loop	0.19259120225906373	0.19010151624679567	previous	1%
future_whenallcomplete_100k_immediately_succeeded_off_loop	0.10164060592651367	0.10232150554656982	current	0%
future_whenallcomplete_100k_immediately_succeeded_on_loop	0.10171210765838623	0.10184358358383179	previous	0%
future_whenallcomplete_100k_deferred_off_loop	0.5959251046180725	0.5962650060653687	current	0%
future_whenallcomplete_100k_deferred_on_loop	0.1757832169532776	0.17523090839385985	previous	0%
future_reduce_10k_futures	0.04979032278060913	0.049446606636047365	previous	0%
future_reduce_into_10k_futures	0.05061229467391968	0.050055181980133055	previous	0%
channel_pipeline_1m_events	0.21894439458847045	0.2216325044631958	current	-1%

significant differences found

[Lukasa]

LGTM, thanks!