[spec proposal] improved API to get validators

[metachris]

Context: https://collective.flashbots.net/t/privacy-concerns-with-data-api/568

We'll update the API for getting validators (https://boost-relay.flashbots.net/relay/v1/data/validator_registration?pubkey=) to make it more private, and to allow bulk queries.

Changes:

1. Instead of only providing pubkey for the request, it will also require fee_recipient (and optionally gas_limit). This is to maintain privacy for proposers (you can only query them if you know the fee_recipient).
2. Allow single queries (like currently), as well as bulk queries with POST requests.
3. Return a response only for active proposers (currently the API returns the result if a proposer registered at any time in the past)

Single query:

https://boost-relay.flashbots.net/relay/v1/data/validator_registration
    ?pubkey=<pubkey>
    ?fee_recipient=<feeRecipient>
    [?gas_limit=<gasLimit>]

Bulk query:

[
  {
    "pubkey": "<a_pubkey>",
    "fee_recipient": "<a_fee_recipient>"
  },
  {
    "pubkey": "<b_pubkey>",
    "fee_recipient": "<b_fee_recipient>",
    "gas_limit": "<b_gas_limit>"
  }
]

Response includes a list of found entries:

[
  "<a_pubkey>",
  "<b_pubkey>"
]

Possible extensions (please comment if you have a need for that, could be added now or in the future):

1. return not only the pubkey but also fee_recipient and gas_limit (enable this response format with another query arg?)
2. return not the found entries, but those that are not found (could also be enabled with another query arg).

---

Please comment with any remaining thoughts. Will start implementation soon 🙏

[jtraglia]

Regarding possible extensions, I like the idea of having another query argument for missing entries; an empty list if everything is found. It seems like the most efficient way for operators to check a large group of validators at once.

Could be as simple as:

• POST /relay/v1/data/validator_registration?missing

[jtraglia]

Semi-related, I think we should remove the timestamp field from /relay/v1/builder/validators response entries:

• https://flashbots.github.io/relay-specs/#/Builder/getValidators

If the registrations are guaranteed to be active, that information isn't required.

[metachris]

Can you please open a new issue re builder/getValidators? (fwiw I disagree because it also includes a signature, which can't be verified without the timestamp. should we also remove the signature?)

[jtraglia]

Ah that's a good point. I'll think about it some more, but yeah I'll open a new issue. Thanks.