Return 404 error if no sync committee contribution is available

[nflaig]

Clarify that 404 status code (error) should be returned if no sync committee contribution is available for the requested beacon_block_root.

See related PR #380 that added the same note for no aggregated attestation available.

[rolfyone]

is the implication here if the block denoted by beacon_block_root is not present?

Are there any other reason we'd not see a contribution?

eg. if i request sync committee contribution from 12 months ago, and only 6 months blocks are stored, then i'd expect 404...

[nflaig]

is the implication here if the block denoted by beacon_block_root is not present?

The two conditions I see where a 404 should be returned is if

• block as denoted by beacon_block_root is not known or not a descendant of the finalized root, as determined by fork choice
• or if beacon node did not prepare a contribution for beacon_block_root, this might be implementation specific but can happen if validator client did not submit a sync committee signature earlier in the slot

eg. if i request sync committee contribution from 12 months ago, and only 6 months blocks are stored, then i'd expect 404...

This API is part of validator APIs which are not intended to serve historical data so I am not sure this is a case we need to consider here. At least in Lodestar we serve this data from a cache which prunes any data from previous slots based on clock slot.

But yes, that would result in a 404 as well..

Unless I am missing something there is no equivalent to getAggregatedAttestation, so would have to request the whole block to get sync committee contributions from 12 months ago.