## Issue Addressed
NA
## Proposed Changes
Our `ERRO` stream has been rather noisy since the merge due to some unexpected behaviours of builders and EEs. Now that we've been running post-merge for a while, I think we can drop some of these `ERRO` to `WARN` so we're not "crying wolf".
The modified logs are:
#### `ERRO Execution engine call failed`
I'm seeing this quite frequently on Geth nodes. They seem to timeout when they're busy and it rarely indicates a serious issue. We also have logging across block import, fork choice updating and payload production that raise `ERRO` or `CRIT` when the EE times out, so I think we're not at risk of silencing actual issues.
#### `ERRO "Builder failed to reveal payload"`
In #3775 we reduced this log from `CRIT` to `ERRO` since it's common for builders to fail to reveal the block to the producer directly whilst still broadcasting it to the networ. I think it's worth dropping this to `WARN` since it's rarely interesting.
I elected to stay with `WARN` since I really do wish builders would fulfill their API promises by returning the block to us. Perhaps I'm just being pedantic here, I could be convinced otherwise.
#### `ERRO "Relay error when registering validator(s)"`
It seems like builders and/or mev-boost struggle to handle heavy loads of validator registrations. I haven't observed issues with validators not actually being registered, but I see timeouts on these endpoints many times a day. It doesn't seem like this `ERRO` is worth it.
#### `ERRO Error fetching block for peer ExecutionLayerErrorPayloadReconstruction`
This means we failed to respond to a peer on the P2P network with a block they requested because of an error in the `execution_layer`. It's very common to see timeouts or incomplete responses on this endpoint whilst the EE is busy and I don't think it's important enough for an `ERRO`. As long as the peer count stays high, I don't think the user needs to be actively concerned about how we're responding to peers.
## Additional Info
NA
* Use Local Payload if More Profitable than Builder
* Rename clone -> clone_from_ref
* Minimize Clones of GetPayloadResponse
* Cleanup & Fix Tests
* Added Tests for Payload Choice by Profit
* Fix Outdated Comments
## Issue Addressed
Recent discussions with other client devs about optimistic sync have revealed a conceptual issue with the optimisation implemented in #3738. In designing that feature I failed to consider that the execution node checks the `blockHash` of the execution payload before responding with `SYNCING`, and that omitting this check entirely results in a degradation of the full node's validation. A node omitting the `blockHash` checks could be tricked by a supermajority of validators into following an invalid chain, something which is ordinarily impossible.
## Proposed Changes
I've added verification of the `payload.block_hash` in Lighthouse. In case of failure we log a warning and fall back to verifying the payload with the execution client.
I've used our existing dependency on `ethers_core` for RLP support, and a new dependency on Parity's `triehash` crate for the Merkle patricia trie. Although the `triehash` crate is currently unmaintained it seems like our best option at the moment (it is also used by Reth, and requires vastly less boilerplate than Parity's generic `trie-root` library).
Block hash verification is pretty quick, about 500us per block on my machine (mainnet).
The optimistic finalized sync feature can be disabled using `--disable-optimistic-finalized-sync` which forces full verification with the EL.
## Additional Info
This PR also introduces a new dependency on our [`metastruct`](https://github.com/sigp/metastruct) library, which was perfectly suited to the RLP serialization method. There will likely be changes as `metastruct` grows, but I think this is a good way to start dogfooding it.
I took inspiration from some Parity and Reth code while writing this, and have preserved the relevant license headers on the files containing code that was copied and modified.
