Bellatrix light client data does not contain the EL block hash, so we
had to follow blocks gossip to learn the EL `block_hash` of such blocks.
Now that Bellatrix is obsolete, we can simplify EL syncing logic under
light client scenarios. Bellatrix light client data can still be used
to advance the light client sync itself, but will no longer result in
`engine_forkchoiceUpdated` calls until the sync reaches Capella. This
also frees up some memory as we no longer have to retain blocks.
The optimistic candidate block check that only imports a new block into
the EL client if its parent block also had execution enabled is not
needed anymore, as mainnet has merged and the attack period is over.
The optimistic sync spec was updated since the LC based optsync module
was introduced. It is no longer necessary to wait for the justified
checkpoint to have execution enabled; instead, any block is okay to be
optimistically imported to the EL client, as long as its parent block
has execution enabled. Complex syncing logic has been removed, and the
LC optsync module will now follow gossip directly, reducing the latency
when using this module. Note that because this is now based on gossip
instead of using sync manager / request manager, that individual blocks
may be missed. However, EL clients should recover from this by fetching
missing blocks themselves.
Etan Kissling
Jacek Sieka
tersec