## Issue Addressed
NA
## Proposed Changes
Avoids reprocessing loops introduced in #4179. (Also somewhat related to #4192).
Breaks the re-queue loop by only re-queuing when an RPC block is received before the attestation creation deadline.
I've put `proposal_is_known` behind a closure to avoid interacting with the `observed_proposers` lock unnecessarily.
## Additional Info
NA
## Issue Addressed
Closes#4185
## Proposed Changes
- Set user agent to `Lighthouse/vX.Y.Z-<commit hash>` by default
- Allow tweaking user agent via `--builder-user-agent "agent"`
## Proposed Changes
Builds on #4028 to use the new payload bodies methods in the HTTP API as well.
## Caveats
The payloads by range method only works for the finalized chain, so it can't be used in the execution engine integration tests because we try to reconstruct unfinalized payloads there.
## Issue Addressed
NA
## Proposed Changes
Apply two changes to code introduced in #4179:
1. Remove the `ERRO` log for when we error on `proposer_has_been_observed()`. We were seeing a lot of this in our logs for finalized blocks and it's a bit noisy.
1. Use `false` rather than `true` for `proposal_already_known` when there is an error. If a block raises an error in `proposer_has_been_observed()` then the block must be invalid, so we should process (and reject) it now rather than queuing it.
For reference, here is one of the offending `ERRO` logs:
```
ERRO Failed to check observed proposers block_root: 0x5845…878e, source: rpc, error: FinalizedBlock { slot: Slot(5410983), finalized_slot: Slot(5411232) }
```
## Additional Info
NA
## Issue Addressed
NA
## Proposed Changes
Similar to #4181 but without the version bump and a more nuanced fix.
Patches the high CPU usage seen after the Capella fork which was caused by processing exits when there are skip slots.
## Additional Info
~~This is an imperfect solution that will cause us to drop some exits at the fork boundary. This is tracked at #4184.~~
## Proposed Changes
We already make some attempts to avoid processing RPC blocks when a block from the same proposer is already being processed through gossip. This PR strengthens that guarantee by using the existing cache for `observed_block_producers` to inform whether an RPC block's processing should be delayed.
## Proposed Changes
This change attempts to prevent failed re-orgs by:
1. Lowering the re-org cutoff from 2s to 1s. This is informed by a failed re-org attempted by @yorickdowne's node. The failed block was requested in the 1.5-2s window due to a Vouch failure, and failed to propagate to the majority of the network before the attestation deadline at 4s.
2. Allow users to adjust their re-org cutoff depending on observed network conditions and their risk profile. The static 2 second cutoff was too rigid.
3. Add a `--proposer-reorg-disallowed-offsets` flag which can be used to prohibit reorgs at certain slots. This is intended to help workaround an issue whereby reorging blocks at slot 1 are currently taking ~1.6s to propagate on gossip rather than ~500ms. This is suspected to be due to a cache miss in current versions of Prysm, which should be fixed in their next release.
## Additional Info
I'm of two minds about removing the `shuffling_stable` check which checks for blocks at slot 0 in the epoch. If we removed it users would be able to configure Lighthouse to try reorging at slot 0, which likely wouldn't work very well due to interactions with the proposer index cache. I think we could leave it for now and revisit it later.
