Broadcast validator registration to all synced beacon nodes

[jimmygchen]

Issue Addressed

The validator client currently publish validator registrations to its first beacon node, and it doesn't require the beacon node to be synced. This could potentially result in registration not being sent to all builders beacon nodes are connected to, because:

• Beacon nodes may be connected to different relays, and only sending it to the first one means registrations may not be sent to all relays.
• Beacon nodes read validator data from the chain, and only send registration for active validators. However if the node is out of sync, it could either be missing the validator or have an outdated status of the validator, resulting in registration for the active validator to be missed.

lighthouse/validator_client/src/preparation_service.rs

Lines 478 to 487 in b4556a3

	match self
	.beacon_nodes
	.first_success(
	RequireSynced::No,
	OfflineOnFailure::No,
	|beacon_node| async move {
	beacon_node.post_validator_register_validator(batch).await
	},
	)
	.await

Proposed Changes

To ensure registrations for all active validators are sent to all relays, we publish validator registration to all synced beacon nodes.

[michaelsproul]

@Mergifyio queue

[mergify]

queue

🛑 The pull request has been removed from the queue default

The queue conditions cannot be satisfied due to failing checks.

You can take a look at Queue: Embarked in merge queue check runs for more details.

In case of a failure due to a flaky test, you should first retrigger the CI.
Then, re-embark the pull request into the merge queue by posting the comment
@mergifyio refresh on the pull request.

[jimmygchen]

@mergify requeue

[mergify]

requeue

✅ This pull request will be re-embarked automatically

The followup queue command will be automatically executed to re-embark the pull request

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 3f82952