Description

The UI requires some extra metrics such as current active validator count and some effective measures of how well a validator is performing.

Although the validator count can in principle be obtained from the standard HTTP API, it is not every efficient.

We should make some efficient version and put them under an endpoint like lighthouse/ui/X

The easiest first endpoint could be:
lighthouse/ui/validator_count

This would read the state and return totals for validators in different states, i.e active, pending, withdrawing, slashed, etc.

For the effectiveness, we might want to measure variables off the form:

• Number of missed head votes
• Attestation rewards
• Percentage missed head votes
• Percentage of full attestation rewards achieved

This could be more complicated to get in an efficient manner. Ideally we would like an endpoint that can get and return these metrics for a list of validators.

If this proves too expensive, perhaps we can retain these metrics for subscribed validators using the validator monitor on the beacon node.