Update `SAMPLES_PER_SLOT` to be number of custody groups instead of data columns. This should have no impact on the current implementation as config currently maintains a `group:subnet:column` ratio of `1:1:1`. **In short, this PR doesn't change anything for Fusaka, but ensures compliance with the spec and potential future changes.**
I've added separate methods to compute sampling columns and custody groups for clarity: `spec.sampling_size_columns` and `spec.sampling_size_custod_groups`
See the clarifications in this PR for more details: https://github.com/ethereum/consensus-specs/pull/4251
N/A
Persist the epoch -> cgc values. This is to ensure that `ValidatorRegistrations::latest_validator_custody_requirement` always returns a `Some` value post restart assuming the `epoch_validator_custody_requirements` map has been updated in the previous runs.
Currently the validator effective balance used for computing PeerDAS custody group count is only updated when the validator subscribes to the BN via `validator/beacon_committee_subscriptions`.
If a validator stops registering with the node, the effective balance gets outdated and stays in the BN memory until the next restart. They are no longer required for CGC computation, as long as the CGC never reduces as per the spec, therefore they can be dropped.
Resolves#6767
This PR implements a basic version of validator custody.
- It introduces a new `CustodyContext` object which contains info regarding number of validators attached to a node and the custody count they contribute to the cgc.
- The `CustodyContext` is added in the da_checker and has methods for returning the current cgc and the number of columns to sample at head. Note that the logic for returning the cgc existed previously in the network globals.
- To estimate the number of validators attached, we use the `beacon_committee_subscriptions` endpoint. This might overestimate the number of validators actually publishing attestations from the node in the case of multi BN setups. We could also potentially use the `publish_attestations` endpoint to get a more conservative estimate at a later point.
- Anytime there's a change in the `custody_group_count` due to addition/removal of validators, the custody context should send an event on a broadcast channnel. The only subscriber for the channel exists in the network service which simply subscribes to more subnets. There can be additional subscribers in sync that will start a backfill once the cgc changes.
TODO
- [ ] **NOT REQUIRED:** Currently, the logic only handles an increase in validator count and does not handle a decrease. We should ideally unsubscribe from subnets when the cgc has decreased.
- [ ] **NOT REQUIRED:** Add a service in the `CustodyContext` that emits an event once `MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS ` passes after updating the current cgc. This event should be picked up by a subscriber which updates the enr and metadata.
- [x] Add more tests
