Phase 0 attestation rewards via Beacon API (#4474)
## Issue Addressed
Addresses #4026.
Beacon-API spec [here](https://ethereum.github.io/beacon-APIs/?urls.primaryName=dev#/Beacon/getAttestationsRewards).
Endpoint: `POST /eth/v1/beacon/rewards/attestations/{epoch}`
This endpoint already supports post-Altair epochs. This PR adds support for phase 0 rewards calculation.
## Proposed Changes
- [x] Attestation rewards API to support phase 0 rewards calculation, re-using logic from `state_processing`. Refactored `get_attestation_deltas` slightly to support computing deltas for a subset of validators.
- [x] Add `inclusion_delay` to `ideal_rewards` (`beacon-API` spec update to follow)
- [x] Add `inactivity` penalties to both `ideal_rewards` and `total_rewards` (`beacon-API` spec update to follow)
- [x] Add tests to compute attestation rewards and compare results with beacon states
## Additional Notes
- The extra penalty for missing attestations or being slashed during an inactivity leak is currently not included in the API response (for both phase 0 and Altair) in the spec.
- I went with adding `inactivity` as a separate component rather than combining them with the 4 rewards, because this is how it was grouped in [the phase 0 spec](https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#get_attestation_deltas). During inactivity leak, all rewards include the optimal reward, and inactivity penalties are calculated separately (see below code snippet from the spec), so it would be quite confusing if we merge them. This would also work better with Altair, because there's no "cancelling" of rewards and inactivity penalties are more separate.
- Altair calculation logic (to include inactivity penalties) to be updated in a follow-up PR.
```python
def get_attestation_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
"""
Return attestation reward/penalty deltas for each validator.
"""
source_rewards, source_penalties = get_source_deltas(state)
target_rewards, target_penalties = get_target_deltas(state)
head_rewards, head_penalties = get_head_deltas(state)
inclusion_delay_rewards, _ = get_inclusion_delay_deltas(state)
_, inactivity_penalties = get_inactivity_penalty_deltas(state)
rewards = [
source_rewards[i] + target_rewards[i] + head_rewards[i] + inclusion_delay_rewards[i]
for i in range(len(state.validators))
]
penalties = [
source_penalties[i] + target_penalties[i] + head_penalties[i] + inactivity_penalties[i]
for i in range(len(state.validators))
]
return rewards, penalties
```
## Example API Response
<details>
<summary>Click me</summary>
```json
{
"ideal_rewards": [
{
"effective_balance": "1000000000",
"head": "6638",
"target": "6638",
"source": "6638",
"inclusion_delay": "9783",
"inactivity": "0"
},
{
"effective_balance": "2000000000",
"head": "13276",
"target": "13276",
"source": "13276",
"inclusion_delay": "19565",
"inactivity": "0"
},
{
"effective_balance": "3000000000",
"head": "19914",
"target": "19914",
"source": "19914",
"inclusion_delay": "29349",
"inactivity": "0"
},
{
"effective_balance": "4000000000",
"head": "26553",
"target": "26553",
"source": "26553",
"inclusion_delay": "39131",
"inactivity": "0"
},
{
"effective_balance": "5000000000",
"head": "33191",
"target": "33191",
"source": "33191",
"inclusion_delay": "48914",
"inactivity": "0"
},
{
"effective_balance": "6000000000",
"head": "39829",
"target": "39829",
"source": "39829",
"inclusion_delay": "58697",
"inactivity": "0"
},
{
"effective_balance": "7000000000",
"head": "46468",
"target": "46468",
"source": "46468",
"inclusion_delay": "68480",
"inactivity": "0"
},
{
"effective_balance": "8000000000",
"head": "53106",
"target": "53106",
"source": "53106",
"inclusion_delay": "78262",
"inactivity": "0"
},
{
"effective_balance": "9000000000",
"head": "59744",
"target": "59744",
"source": "59744",
"inclusion_delay": "88046",
"inactivity": "0"
},
{
"effective_balance": "10000000000",
"head": "66383",
"target": "66383",
"source": "66383",
"inclusion_delay": "97828",
"inactivity": "0"
},
{
"effective_balance": "11000000000",
"head": "73021",
"target": "73021",
"source": "73021",
"inclusion_delay": "107611",
"inactivity": "0"
},
{
"effective_balance": "12000000000",
"head": "79659",
"target": "79659",
"source": "79659",
"inclusion_delay": "117394",
"inactivity": "0"
},
{
"effective_balance": "13000000000",
"head": "86298",
"target": "86298",
"source": "86298",
"inclusion_delay": "127176",
"inactivity": "0"
},
{
"effective_balance": "14000000000",
"head": "92936",
"target": "92936",
"source": "92936",
"inclusion_delay": "136959",
"inactivity": "0"
},
{
"effective_balance": "15000000000",
"head": "99574",
"target": "99574",
"source": "99574",
"inclusion_delay": "146742",
"inactivity": "0"
},
{
"effective_balance": "16000000000",
"head": "106212",
"target": "106212",
"source": "106212",
"inclusion_delay": "156525",
"inactivity": "0"
},
{
"effective_balance": "17000000000",
"head": "112851",
"target": "112851",
"source": "112851",
"inclusion_delay": "166307",
"inactivity": "0"
},
{
"effective_balance": "18000000000",
"head": "119489",
"target": "119489",
"source": "119489",
"inclusion_delay": "176091",
"inactivity": "0"
},
{
"effective_balance": "19000000000",
"head": "126127",
"target": "126127",
"source": "126127",
"inclusion_delay": "185873",
"inactivity": "0"
},
{
"effective_balance": "20000000000",
"head": "132766",
"target": "132766",
"source": "132766",
"inclusion_delay": "195656",
"inactivity": "0"
},
{
"effective_balance": "21000000000",
"head": "139404",
"target": "139404",
"source": "139404",
"inclusion_delay": "205439",
"inactivity": "0"
},
{
"effective_balance": "22000000000",
"head": "146042",
"target": "146042",
"source": "146042",
"inclusion_delay": "215222",
"inactivity": "0"
},
{
"effective_balance": "23000000000",
"head": "152681",
"target": "152681",
"source": "152681",
"inclusion_delay": "225004",
"inactivity": "0"
},
{
"effective_balance": "24000000000",
"head": "159319",
"target": "159319",
"source": "159319",
"inclusion_delay": "234787",
"inactivity": "0"
},
{
"effective_balance": "25000000000",
"head": "165957",
"target": "165957",
"source": "165957",
"inclusion_delay": "244570",
"inactivity": "0"
},
{
"effective_balance": "26000000000",
"head": "172596",
"target": "172596",
"source": "172596",
"inclusion_delay": "254352",
"inactivity": "0"
},
{
"effective_balance": "27000000000",
"head": "179234",
"target": "179234",
"source": "179234",
"inclusion_delay": "264136",
"inactivity": "0"
},
{
"effective_balance": "28000000000",
"head": "185872",
"target": "185872",
"source": "185872",
"inclusion_delay": "273918",
"inactivity": "0"
},
{
"effective_balance": "29000000000",
"head": "192510",
"target": "192510",
"source": "192510",
"inclusion_delay": "283701",
"inactivity": "0"
},
{
"effective_balance": "30000000000",
"head": "199149",
"target": "199149",
"source": "199149",
"inclusion_delay": "293484",
"inactivity": "0"
},
{
"effective_balance": "31000000000",
"head": "205787",
"target": "205787",
"source": "205787",
"inclusion_delay": "303267",
"inactivity": "0"
},
{
"effective_balance": "32000000000",
"head": "212426",
"target": "212426",
"source": "212426",
"inclusion_delay": "313050",
"inactivity": "0"
}
],
"total_rewards": [
{
"validator_index": "0",
"head": "212426",
"target": "212426",
"source": "212426",
"inclusion_delay": "313050",
"inactivity": "0"
},
{
"validator_index": "32",
"head": "212426",
"target": "212426",
"source": "212426",
"inclusion_delay": "313050",
"inactivity": "0"
},
{
"validator_index": "63",
"head": "-357771",
"target": "-357771",
"source": "-357771",
"inclusion_delay": "0",
"inactivity": "0"
}
]
}
```
</details>
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