ADR: Stateless transaction observation & construction

[ch1bo]

Drafts a way to make the chain layer use no head state specific information to construct and observe transactions. In fact, by using ResolvedTx, the observation becomes fully stateless. For constructing head protocol transactions, one still needs to keep relevant UTxO around and any information to be able to spend them (SpendableUTxO).

A rough proof of concept is currently available on branch ch1bo/stateless-hack.

TODO:

• Gather ideas and resolve discussion points (TBD in document)

---

• CHANGELOG updated or not needed
• Documentation updated or not needed
• Haddocks updated or not needed
• No new TODOs introduced or explained herafter

[github-actions]

Transactions Costs

Sizes and execution budgets for Hydra protocol transactions. Note that unlisted parameters are currently using arbitrary values and results are not fully deterministic and comparable to previous runs.

Metadata
Generated at	2023-09-18 15:19:30.994227559 UTC
Max. memory units	14000000
Max. CPU units	10000000000
Max. tx size (kB)	16384

Script summary

Name	Hash	Size (Bytes)
νInitial	3ffaf6b87df35cb01a52eb23032b8f0b1a2a3ad3acf0930abc9c833a	4150
νCommit	e4c32d6dc83b2917aa7805571f30437ad98b6d20d821d34d45943755	2093
νHead	8a43c1c4d5cb60c212e7aa540932f311cb914a1b6104f0f36a2aaaf0	8845
μHead	efd460b736e8155861e909d6507760b24a5c28717591c6e98c26b104*	4187

• The minting policy hash is only usable for comparison. As the script is parameterized, the actual script is unique per Head.

Cost of Init Transaction

Parties	Tx size	% max Mem	% max CPU	Min fee ₳
1	4782	12.19	4.81	0.49
2	4985	14.24	5.57	0.52
3	5191	16.69	6.51	0.56
5	5598	21.25	8.24	0.63
10	6629	33.24	12.80	0.80
38	12367	99.85	38.14	1.78

Cost of Commit Transaction

This is using ada-only outputs for better comparability.

UTxO	Tx size	% max Mem	% max CPU	Min fee ₳
1	599	12.75	5.01	0.32
2	787	16.41	6.66	0.37
3	974	20.37	8.42	0.42
5	1348	28.46	12.01	0.53
10	2288	51.35	21.96	0.82
18	3775	95.35	40.55	1.38

Cost of CollectCom Transaction

Parties	UTxO (bytes)	Tx size	% max Mem	% max CPU	Min fee ₳
1	57	813	24.07	9.57	0.45
2	114	1136	36.88	14.81	0.61
3	169	1455	54.78	22.04	0.82
4	225	1775	69.98	28.43	1.00
5	282	2095	90.47	36.88	1.24

Cost of Close Transaction

Parties	Tx size	% max Mem	% max CPU	Min fee ₳
1	694	19.27	8.85	0.40
2	945	20.74	10.36	0.43
3	1074	22.41	11.70	0.46
5	1590	26.36	15.24	0.54
10	2598	34.42	22.62	0.71
49	7211	82.09	42.56	1.44

Cost of Contest Transaction

Parties	Tx size	% max Mem	% max CPU	Min fee ₳
1	739	23.18	10.34	0.44
2	951	25.14	11.99	0.48
3	1175	27.10	13.67	0.52
5	1580	30.54	16.62	0.59
10	2638	39.37	24.46	0.76
43	9461	99.52	76.05	1.92

Cost of Abort Transaction

Some variation because of random mixture of still initial and already committed outputs.

Parties	Tx size	% max Mem	% max CPU	Min fee ₳
1	4999	21.63	9.30	0.61
2	5179	31.54	13.46	0.73
3	5947	54.71	23.94	1.03
4	6112	69.28	30.16	1.20
5	6500	93.54	40.83	1.49

Cost of FanOut Transaction

Involves spending head output and burning head tokens. Uses ada-only UTxO for better comparability.

Parties	UTxO	UTxO (bytes)	Tx size	% max Mem	% max CPU	Min fee ₳
5	0	0	4800	8.80	3.70	0.46
5	1	57	4840	10.11	4.50	0.48
5	5	285	4984	15.10	7.59	0.55
5	10	569	5168	21.75	11.62	0.64
5	20	1138	5522	34.88	19.61	0.82
5	30	1707	5883	48.43	27.77	1.00
5	40	2275	6245	61.40	35.71	1.18
5	50	2846	6598	73.92	43.45	1.35
5	69	3925	7281	99.52	58.92	1.70

[github-actions]

Test Results

358 tests  ±0   353 ✔️ ±0   22m 18s ⏱️ +25s
121 suites ±0       5 💤 ±0 
    6 files   ±0       0 ❌ ±0 

Results for commit 5524d5b. ± Comparison against base commit ec6c7a2.

♻️ This comment has been updated with latest results.