[Draft, do-not-merge] Send response from within application code

[eddyashton]

Extremely DRAFT, just opening for an easy diff view while I break out some of the standalone changes into separate PRs. This will likely remain a monster, but hopefully (eventually) an explicable one.

Implementation of #4219.

Headlines:

• Loads of renames in the http:: namespace to clarify concepts, and avoid reuse of Endpoint. The main one is that Endpoint becomes Session
• HTTP/2 implementation squeezed closer to HTTP/1.1, by separating a Parser object from the Session, and moving all the callbacks to a separate file
• Making tls::Session a member-of rather than base-class-of the HTTPSession and HTTP2Session. Simplifies the class hierarchy, though it remains complex, and opens the door for a plain-text IO layer for all sessions
• Broader use of std::span<const uint8_t>. I think this removes a bunch of unnecessary copies as we switch between moved vectors and raw pointers, but it enforces a single eventual copy. I dunno, I think its simpler to read regardless

The core difficulty, which I hadn't grokked before I was deep into the weeds, is the need for additional info in lookup -between a HTTP/1.1 session which can be looked up or referenced by a single ConnID, and a HTTP/2 session which sometimes needs an additional StreamId. In particular to respond to an actual request, we need a StreamId, but for early parsing errors/parity with HTTP/1.1, we may not have one. I think the right approach here is to break the concepts of a lifetime-managed TLS socket, from a writeable/readable request/response stream. This is 1-to-1 in HTTP/1.1, but 1-to-many in HTTP/2. This is partially done in this PR, with multiple HTTPResponders per HTTP2ServerSession, but this is incomplete.

[ccf-bot]

expose_forwarding@52002 aka 20221024.34 vs main ewma over 20 builds from 51552 to 51959

Click to see table

main

build_id	build_number	tpcc_virtual_cft^	tpcc_virtual_cft_mem	ls_virtual_cft^	ls_virtual_cft_mem	ls_jwt_virtual_cft^	ls_jwt_virtual_cft_mem	ls_js_virtual_cft^	ls_js_virtual_cft_mem	ls_full_js_virtual_cft^	ls_full_js_virtual_cft_mem	ls_js_jwt_virtual_cft^	ls_js_jwt_virtual_cft_mem	hist_sgx_cft^	tpcc_sgx_cft^	tpcc_sgx_cft_mem	ls_sgx_cft^	ls_sgx_cft_mem	ls_jwt_sgx_cft^	ls_jwt_sgx_cft_mem	ls_js_sgx_cft^	ls_js_sgx_cft_mem	ls_full_js_sgx_cft^	ls_full_js_sgx_cft_mem	ls_js_jwt_sgx_cft^	ls_js_jwt_sgx_cft_mem	RB put (/s)^	CHAMP put (/s)^	RB get (/s)^	CHAMP get (/s)^
51552	20221018.55	8720.44	0	34911.7	0	9261.82	0	4085.74	0	3347.54	0	3197.54	0	24649.6	6425.99	8.3497e+07	20823.3	1.63882e+07	6505.01	1.58639e+07	2485.32	1.00967e+07	2095.18	9.31027e+06	2010.82	9.31027e+06	917639	1.37977e+06	9.27952e+06	3.63121e+07
51560	20221019.3	11252.2	0	37041	0	10152.8	0	4368.85	0	3403.13	0	3365.06	0	28778.6	6359.85	8.3497e+07	20749	1.63882e+07	6418.94	1.58639e+07	2490.69	9.83456e+06	2105.81	9.31027e+06	2036.1	9.04813e+06	908117	1.37624e+06	9.41168e+06	3.66362e+07
51568	20221019.7	10865.4	0	37837.3	0	10050.4	0	4574.09	0	3426.37	0	3507.21	0	21129.7	5745.73	8.37592e+07	17946.8	1.71746e+07	6045.94	1.53396e+07	2356.59	9.83456e+06	1999.41	1.08831e+07	1975.93	9.31027e+06	905101	1.37374e+06	9.29629e+06	3.54933e+07
51596	20221019.17	9898.13	0	36578.3	0	9638.42	0	4265.05	0	3362.88	0	3199.59	0	23518.8	5697	8.29727e+07	17157.3	1.69124e+07	6161.39	1.56017e+07	2411.73	9.57242e+06	2017.64	9.31027e+06	1931.15	9.31027e+06	911715	1.37145e+06	9.17148e+06	3.58669e+07
51626	20221019.27	11126.6	0	42087	0	10128.4	0	4248.36	0	3590.06	0	3264.35	0	27871.7	5640.83	8.29727e+07	17643	1.58639e+07	6155.07	1.53396e+07	2345.98	9.57242e+06	1981.41	9.57242e+06	1930.93	9.04813e+06	911634	1.36897e+06	9.06993e+06	3.51884e+07
51650	20221020.3	11472.4	0	41541.8	0	10031.5	0	4301.53	0	3539.77	0	3209.56	0	28253.1	5786.4	8.27106e+07	18023.8	1.58639e+07	6135.44	1.56017e+07	2369.1	9.57242e+06	1991.09	9.57242e+06	1934.73	9.04813e+06	905029	1.39168e+06	9.22934e+06	3.56174e+07
51670	20221020.10	11143.3	0	42769.6	0	10308.8	0	4367.85	0	3535.13	0	3305.8	0	29115.5	5718.02	8.32349e+07	17836.8	1.69124e+07	6100.99	1.58639e+07	2367.39	9.57242e+06	1941.56	9.57242e+06	1923.17	9.31027e+06	891086	1.38743e+06	9.18789e+06	3.58036e+07
51694	20221020.18	10569.2	0	40721.7	0	10547.6	0	4237.22	0	3461.38	0	3256.86	0	20991.9	5528.74	8.29727e+07	17709.3	1.63882e+07	6105.49	1.56017e+07	2315.14	9.83456e+06	1981.1	9.57242e+06	1918.74	9.31027e+06	904667	1.39054e+06	9.45513e+06	3.60557e+07
51756	20221020.38	11145.5	0	43326.1	0	10685.5	0	4313.24	0	3571.63	0	3227.65	0	24478.8	5617	8.32349e+07	17658.7	1.66503e+07	6143.66	1.53396e+07	2350.65	9.83456e+06	2019.9	9.31027e+06	1928.99	9.57242e+06	897688	1.33107e+06	9.0981e+06	3.54939e+07
51800	20221020.52	11474.6	0	43005.4	0	10189.3	0	4329.56	0	3606.16	0	3095.43	0	24480.9	5792.02	8.42835e+07	17941.5	1.66503e+07	6099.91	1.56017e+07	2362.63	9.31027e+06	1984.09	9.57242e+06	1917.09	9.57242e+06	904628	1.37902e+06	9.22934e+06	3.56794e+07
51805	20221021.2	11181.3	0	42683.3	0	10188.4	0	4351.77	0	3461.51	0	3212.55	0	26940	5750.81	8.3497e+07	17709.5	1.71746e+07	6168.59	1.56017e+07	2345.54	9.57242e+06	1996.68	9.57242e+06	1921.35	9.04813e+06	902870	1.3806e+06	9.27948e+06	3.58669e+07
51813	20221021.5	11336.7	0	40642.5	0	11519.1	0	4260.82	0	3425.09	0	3223.42	0	28834.2	5793.12	8.3497e+07	17799.1	1.6126e+07	6120.3	1.56017e+07	2348.47	9.57242e+06	2044.46	9.31027e+06	1910.74	9.04813e+06	907679	1.37643e+06	9.22103e+06	3.59298e+07
51826	20221021.9	10567.1	0	42390.5	0	10341.2	0	4289.94	0	3385.16	0	3174.02	0	26911.8	5621.67	8.24484e+07	17870.6	1.6126e+07	6151.43	1.56017e+07	2357.11	9.57242e+06	1980.47	9.31027e+06	1926.41	9.04813e+06	885814	1.34551e+06	9.13063e+06	3.53713e+07
51832	20221021.11	10984.6	0	43765.1	0	10141	0	4366.3	0	3463.29	0	3228.09	0	24824.9	5611.78	8.3497e+07	17968.1	1.63882e+07	6067.88	1.56017e+07	2340.66	9.57242e+06	1975.36	9.57242e+06	1877.25	9.04813e+06	891090	1.36788e+06	9.21273e+06	3.56174e+07
51844	20221021.15	10939.3	0	42325.1	0	10632.1	0	4249.92	0	3457.66	0	3218.37	0	23210.3	5666.7	8.42835e+07	17806.4	1.63882e+07	6079.43	1.56017e+07	2310.1	9.57242e+06	2004.41	9.31027e+06	1914.02	9.31027e+06	908278	1.37283e+06	9.22099e+06	3.57411e+07
51922	20221023.1	11341.2	0	42755.5	0	10599.5	0	4421.86	0	3478.67	0	3215.35	0	24171.6	5780.97	8.21863e+07	17755.2	1.6126e+07	6062.06	1.53396e+07	2339.54	9.57242e+06	1976.51	9.57242e+06	1923.12	9.04813e+06	908401	1.36688e+06	9.14686e+06	3.57417e+07
51929	20221024.2	11020	0	42507.8	0	10714.4	0	4234.49	0	3585.69	0	3241.89	0	21619.3	5649.55	8.32349e+07	18197.1	1.66503e+07	6173.25	1.58639e+07	2353.95	9.31027e+06	1956.4	1.14074e+07	1881.83	9.04813e+06	924057	1.38349e+06	9.30901e+06	3.57411e+07
51934	20221024.4	11228.6	0	43074.1	0	10611.6	0	4309.36	0	3534.43	0	3202.17	0	28527.6	5696.81	8.37592e+07	17882.1	1.6126e+07	6157.47	1.58639e+07	2348.42	9.31027e+06	1978.09	1.27181e+07	1930.14	9.31027e+06	905468	1.35252e+06	9.41601e+06	3.56794e+07
51943	20221024.8	11138.8	0	41682.8	0	10100.2	0	4213.87	0	3372.76	0	3197.46	0	24870.3	5747.57	8.37592e+07	17784.2	1.63882e+07	6134.12	1.56017e+07	2359.15	9.83456e+06	1984.33	9.83456e+06	1930.04	9.31027e+06	898869	1.37809e+06	9.39876e+06	3.58669e+07
51959	20221024.15	11371.8	0	42816.8	0	10018.8	0	4301.09	0	3541.08	0	3206.07	0	24628.2	5782.18	8.45456e+07	17690.6	1.6126e+07	6032.81	1.56017e+07	2359.2	9.57242e+06	1980.58	9.57242e+06	1914.75	9.04813e+06	920195	1.36952e+06	9.33446e+06	3.58669e+07

expose_forwarding

build_id	build_number	tpcc_virtual_cft^	tpcc_virtual_cft_mem	ls_virtual_cft^	ls_virtual_cft_mem	tpcc_sgx_cft^	tpcc_sgx_cft_mem	ls_jwt_virtual_cft^	ls_jwt_virtual_cft_mem	ls_js_virtual_cft^	ls_js_virtual_cft_mem	ls_sgx_cft^	ls_sgx_cft_mem	ls_full_js_virtual_cft^	ls_full_js_virtual_cft_mem	ls_jwt_sgx_cft^	ls_jwt_sgx_cft_mem	ls_js_jwt_virtual_cft^	ls_js_jwt_virtual_cft_mem	ls_js_sgx_cft^	ls_js_sgx_cft_mem	ls_full_js_sgx_cft^	ls_full_js_sgx_cft_mem	hist_sgx_cft^	ls_js_jwt_sgx_cft^	ls_js_jwt_sgx_cft_mem	RB put (/s)^	CHAMP put (/s)^	RB get (/s)^	CHAMP get (/s)^
51842	20221021.14	11168.9	0	40979.1	0	5603.1	8.37592e+07	10405.9	0	4316.21	0	17592	1.6126e+07	3523.1	0	6549.29	1.56017e+07	3246.57	0	2352.35	9.57242e+06	1980	9.31027e+06	21898.8	1926.45	9.04813e+06	906870	1.38555e+06	9.21269e+06	3.56174e+07
51848	20221021.16	11364.3	0	43358.9	0	5658.82	8.32349e+07	10138.2	0	4456.01	0	17703.3	1.6126e+07	3572.58	0	5981.75	1.53396e+07	3260.47	0	2352.14	9.57242e+06	1984.48	9.57242e+06	25142	1926.69	9.31027e+06	904527	1.37157e+06	9.22124e+06	3.55556e+07
51851	20221021.17	11176.3	0	44090.4	0	5729.32	8.29727e+07	10212	0	4263.98	0	17671.2	1.63882e+07	3493.24	0	6020.59	1.56017e+07	3218	0	2360.35	9.57242e+06	1987.43	9.57242e+06	21840.1	1914.63	9.31027e+06	889539	1.38107e+06	9.39445e+06	3.58663e+07
51993	20221024.30	10975.4	0	40992.4	0	5601.91	8.40213e+07	10010.2	0	4349.52	0	17620.9	1.6126e+07	3464.4	0	6029.57	1.53396e+07	3218.13	0	2361.91	9.57242e+06	1983.84	9.57242e+06	25266.4	1913.11	9.04813e+06	881347	1.37136e+06	9.3601e+06	3.58663e+07
52002	20221024.34	11265.9	0	43190.2	0	5604.41	8.29727e+07	10703	0	4307.4	0	17652.2	1.6126e+07	3413.27	0	6128.9	1.56017e+07	3231.6	0	2367.94	9.57242e+06	1984.36	9.57242e+06	26975.2	1928.18	9.04813e+06	877306	1.37338e+06	9.20441e+06	3.58669e+07

[eddyashton]

Most are rename suggestions. For some context, when variable names are single/double lettered and (for example) are declared in line 1, one can quickly forget what that represents in line 20 or so. Sometimes F12 in VSCode also becomes quite tricky to do it on one or two lettered variables.

Otherwise, nice work on this change!

@MahatiC Thanks, I've renamed the short variables as suggested :)

[eddyashton]

/azp run

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