This PR address the following spec change: https://github.com/ethereum/consensus-specs/pull/3312
Instead of subscribing to a long-lived subnet for every attached validator to a beacon node, all beacon nodes will subscribe to `SUBNETS_PER_NODE` long-lived subnets. This is currently set to 2 for mainnet.
This PR does not include any scoring or advanced discovery mechanisms. A future PR will improve discovery and we can implement scoring after the next hard fork when we expect all client teams and all implementations to respect this spec change.
This will be a significant change in the subnet network structure for consensus clients and we will likely have to monitor and tweak our peer management logic.
## Issue Addressed
NA
## Proposed Changes
Adds metrics to track validators that are submitting equivocating (but not slashable) sync messages. This follows on from some research we've been doing in a separate fork of LH.
## Additional Info
@jimmygchen and @michaelsproul have already run their eyes over this so it should be easy to get into v4.2.0, IMO.
## Issue Addressed
NA
## Proposed Changes
Adds an additional check to a feature introduced in #4179 to prevent us from re-queuing already-known blocks that could be rejected immediately.
## Additional Info
Ideally this would have been included in v4.1.0, however we came across it too late to release it safely. We decided that the safest path forward is to release *without* this check and then patch it in the next version. The lack of this check should only result in a very minor performance impact (the impact is totally negligible in my assessment).
## Issue Addressed
NA
## Proposed Changes
Adds a flag to store invalid blocks on disk for teh debugz. Only *some* invalid blocks are stored, those which:
- Were received via gossip (rather than RPC, for instance)
- This keeps things simple to start with and should capture most blocks.
- Passed gossip verification
- This reduces the ability for random people to fill up our disk. A proposer signature is required to write something to disk.
## Additional Info
It's possible that we'll store blocks that aren't necessarily invalid, but we had an internal error during verification. Those blocks seem like they might be useful sometimes.
This commit adds a check to the networking service when handling core gossipsub topic subscription requests. If the BN is already subscribed to the core topics, we won't attempt to resubscribe.
## Issue Addressed
#4258
## Proposed Changes
- In the networking service, check if we're already subscribed to all of the core gossipsub topics and, if so, do nothing
## Additional Info
N/A
## Limit Backfill Sync
This PR transitions Lighthouse from syncing all the way back to genesis to only syncing back to the weak subjectivity point (~ 5 months) when syncing via a checkpoint sync.
There are a number of important points to note with this PR:
- Firstly and most importantly, this PR fundamentally shifts the default security guarantees of checkpoint syncing in Lighthouse. Prior to this PR, Lighthouse could verify the checkpoint of any given chain by ensuring the chain eventually terminates at the corresponding genesis. This guarantee can still be employed via the new CLI flag --genesis-backfill which will prompt lighthouse to the old behaviour of downloading all blocks back to genesis. The new behaviour only checks the proposer signatures for the last 5 months of blocks but cannot guarantee the chain matches the genesis chain.
- I have not modified any of the peer scoring or RPC responses. Clients syncing from gensis, will downscore new Lighthouse peers that do not possess blocks prior to the WSP. This is by design, as Lighthouse nodes of this form, need a mechanism to sort through peers in order to find useful peers in order to complete their genesis sync. We therefore do not discriminate between empty/error responses for blocks prior or post the local WSP. If we request a block that a peer does not posses, then fundamentally that peer is less useful to us than other peers.
- This will make a radical shift in that the majority of nodes will no longer store the full history of the chain. In the future we could add a pruning mechanism to remove old blocks from the db also.
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## Issue Addressed
#4150
## Proposed Changes
Maintain trusted peers in the pruning logic. ~~In principle the changes here are not necessary as a trusted peer has a max score (100) and all other peers can have at most 0 (because we don't implement positive scores). This means that we should never prune trusted peers unless we have more trusted peers than the target peer count.~~
This change shifts this logic to explicitly never prune trusted peers which I expect is the intuitive behaviour.
~~I suspect the issue in #4150 arises when a trusted peer disconnects from us for one reason or another and then we remove that peer from our peerdb as it becomes stale. When it re-connects at some large time later, it is no longer a trusted peer.~~
Currently we do disconnect trusted peers, and this PR corrects this to maintain trusted peers in the pruning logic.
As suggested in #4150 we maintain trusted peers in the db and thus we remember them even if they disconnect from us.
* Update Engine API to Latest
* Get Mock EE Working
* Fix Mock EE
* Update Engine API Again
* Rip out get_blobs_bundle Stuff
* Fix Test Harness
* Fix Clippy Complaints
* Fix Beacon Chain Tests
It is a well-known fact that IP addresses for beacon nodes used by specific validators can be de-anonymized. There is an assumed risk that a malicious user may attempt to DOS validators when producing blocks to prevent chain growth/liveness.
Although there are a number of ideas put forward to address this, there a few simple approaches we can take to mitigate this risk.
Currently, a Lighthouse user is able to set a number of beacon-nodes that their validator client can connect to. If one beacon node is taken offline, it can fallback to another. Different beacon nodes can use VPNs or rotate IPs in order to mask their IPs.
This PR provides an additional setup option which further mitigates attacks of this kind.
This PR introduces a CLI flag --proposer-only to the beacon node. Setting this flag will configure the beacon node to run with minimal peers and crucially will not subscribe to subnets or sync committees. Therefore nodes of this kind should not be identified as nodes connected to validators of any kind.
It also introduces a CLI flag --proposer-nodes to the validator client. Users can then provide a number of beacon nodes (which may or may not run the --proposer-only flag) that the Validator client will use for block production and propagation only. If these nodes fail, the validator client will fallback to the default list of beacon nodes.
Users are then able to set up a number of beacon nodes dedicated to block proposals (which are unlikely to be identified as validator nodes) and point their validator clients to produce blocks on these nodes and attest on other beacon nodes. An attack attempting to prevent liveness on the eth2 network would then need to preemptively find and attack the proposer nodes which is significantly more difficult than the default setup.
This is a follow on from: #3328
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## 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
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
## 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.
## Issue Addressed
N/A
## Proposed Changes
Adds a flag for disabling peer scoring. This is useful for local testing and testing small networks for new features.
## Issue Addressed
#3212
## Proposed Changes
- Introduce a new `rate_limiting_backfill_queue` - any new inbound backfill work events gets immediately sent to this FIFO queue **without any processing**
- Spawn a `backfill_scheduler` routine that pops a backfill event from the FIFO queue at specified intervals (currently halfway through a slot, or at 6s after slot start for 12s slots) and sends the event to `BeaconProcessor` via a `scheduled_backfill_work_tx` channel
- This channel gets polled last in the `InboundEvents`, and work event received is wrapped in a `InboundEvent::ScheduledBackfillWork` enum variant, which gets processed immediately or queued by the `BeaconProcessor` (existing logic applies from here)
Diagram comparing backfill processing with / without rate-limiting:
https://github.com/sigp/lighthouse/issues/3212#issuecomment-1386249922
See this comment for @paulhauner's explanation and solution: https://github.com/sigp/lighthouse/issues/3212#issuecomment-1384674956
## Additional Info
I've compared this branch (with backfill processing rate limited to to 1 and 3 batches per slot) against the latest stable version. The CPU usage during backfill sync is reduced by ~5% - 20%, more details on this page:
https://hackmd.io/@jimmygchen/SJuVpJL3j
The above testing is done on Goerli (as I don't currently have hardware for Mainnet), I'm guessing the differences are likely to be bigger on mainnet due to block size.
### TODOs
- [x] Experiment with processing multiple batches per slot. (need to think about how to do this for different slot durations)
- [x] Add option to disable rate-limiting, enabed by default.
- [x] (No longer required now we're reusing the reprocessing queue) Complete the `backfill_scheduler` task when backfill sync is completed or not required
* rename 4844 to deneb
* rename 4844 to deneb
* move excess data gas field
* get EF tests working
* fix ef tests lint
* fix the blob identifier ef test
* fix accessed files ef test script
* get beacon chain tests passing
* introduce availability pending block
* add intoavailableblock trait
* small fixes
* add 'gossip blob cache' and start to clean up processing and transition types
* shard memory blob cache
* Initial commit
* Fix after rebase
* Add gossip verification conditions
* cache cleanup
* general chaos
* extended chaos
* cargo fmt
* more progress
* more progress
* tons of changes, just tryna compile
* everything, everywhere, all at once
* Reprocess an ExecutedBlock on unavailable blobs
* Add sus gossip verification for blobs
* Merge stuff
* Remove reprocessing cache stuff
* lint
* Add a wrapper to allow construction of only valid `AvailableBlock`s
* rename blob arc list to blob list
* merge cleanuo
* Revert "merge cleanuo"
This reverts commit 5e98326878c77528d0c4668c5a4db4a4b0fbaeaa.
* Revert "Revert "merge cleanuo""
This reverts commit 3a4009443a5812b3028abe855079307436dc5419.
* fix rpc methods
* move beacon block and blob to eth2/types
* rename gossip blob cache to data availability checker
* lots of changes
* fix some compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* cargo fmt
* use a common data structure for block import types
* fix availability check on proposal import
* refactor the blob cache and split the block wrapper into two types
* add type conversion for signed block and block wrapper
* fix beacon chain tests and do some renaming, add some comments
* Partial processing (#4)
* move beacon block and blob to eth2/types
* rename gossip blob cache to data availability checker
* lots of changes
* fix some compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* fix compilation issues
* cargo fmt
* use a common data structure for block import types
* fix availability check on proposal import
* refactor the blob cache and split the block wrapper into two types
* add type conversion for signed block and block wrapper
* fix beacon chain tests and do some renaming, add some comments
* cargo update (#6)
---------
Co-authored-by: realbigsean <sean@sigmaprime.io>
Co-authored-by: realbigsean <seananderson33@gmail.com>
## Issue Addressed
NA
## Proposed Changes
Replaces #4058 to attempt to reduce `ERRO Failed to send scheduled attestation` spam and provide more information for diagnosis. With this PR we achieve:
- When dequeuing attestations after a block is received, send only one log which reports `n` failures (rather than `n` logs reporting `n` failures).
- Make a distinction in logs between two separate attestation dequeuing events.
- Add more information to both log events to help assist with troubleshooting.
## Additional Info
NA
## Issue Addressed
Closes#3814, replaces #3818.
## Proposed Changes
* Add a WARN log for the case where we are attempting to sync chain segments but can't process them because they're building on an invalid parent. The most common case where we see this is when the execution node database is corrupt, causing sync to stall mysteriously (because we're currently logging the failure only at debug level).
* Additionally I've bumped up the logging for invalid execution payloads to `WARN`. This may result in some duplicate logs as we log errors from the `beacon_chain` and then again from the beacon processor. Invalid payloads and corrupt DBs _should_ be rare enough that this doesn't produce overwhelming log volume.
There is a race condition which occurs when multiple discovery queries return at almost the exact same time and they independently contain a useful peer we would like to connect to.
The condition can occur that we can add the same peer to the dial queue, before we get a chance to process the queue.
This ends up displaying an error to the user:
```
ERRO Dialing an already dialing peer
```
Although this error is harmless it's not ideal.
There are two solutions to resolving this:
1. As we decide to dial the peer, we change the state in the peer-db to dialing (before we add it to the queue) which would prevent other requests from adding to the queue.
2. We prevent duplicates in the dial queue
This PR has opted for 2. because 1. will complicate the code in that we are changing states in non-intuitive places. Although this technically adds a very slight performance cost, its probably a cleaner solution as we can keep the state-changing logic in one place.
* update docs
* introduce a temp enum to model an adjusted `BlockWrapper` and fix blob coupling
* fix compilation issue
* fix blob coupling in the network context
* review comments
## Issue Addressed
#3938
## Proposed Changes
- `network::Processor` is deleted and all it's logic is moved to `network::Router`.
- The `network::Router` module is moved to a single file.
- The following functions are deleted: `on_disconnect` `send_status` `on_status_response` `on_blocks_by_root_request` `on_lightclient_bootstrap` `on_blocks_by_range_request` `on_block_gossip` `on_unaggregated_attestation_gossip` `on_aggregated_attestation_gossip` `on_voluntary_exit_gossip` `on_proposer_slashing_gossip` `on_attester_slashing_gossip` `on_sync_committee_signature_gossip` `on_sync_committee_contribution_gossip` `on_light_client_finality_update_gossip` `on_light_client_optimistic_update_gossip`. This deletions are possible because the updated `Router` allows the underlying methods to be called directly.
## Issue Addressed
Add support for ipv6 and dual stack in lighthouse.
## Proposed Changes
From an user perspective, now setting an ipv6 address, optionally configuring the ports should feel exactly the same as using an ipv4 address. If listening over both ipv4 and ipv6 then the user needs to:
- use the `--listen-address` two times (ipv4 and ipv6 addresses)
- `--port6` becomes then required
- `--discovery-port6` can now be used to additionally configure the ipv6 udp port
### Rough list of code changes
- Discovery:
- Table filter and ip mode set to match the listening config.
- Ipv6 address, tcp port and udp port set in the ENR builder
- Reported addresses now check which tcp port to give to libp2p
- LH Network Service:
- Can listen over Ipv6, Ipv4, or both. This uses two sockets. Using mapped addresses is disabled from libp2p and it's the most compatible option.
- NetworkGlobals:
- No longer stores udp port since was not used at all. Instead, stores the Ipv4 and Ipv6 TCP ports.
- NetworkConfig:
- Update names to make it clear that previous udp and tcp ports in ENR were Ipv4
- Add fields to configure Ipv6 udp and tcp ports in the ENR
- Include advertised enr Ipv6 address.
- Add type to model Listening address that's either Ipv4, Ipv6 or both. A listening address includes the ip, udp port and tcp port.
- UPnP:
- Kept only for ipv4
- Cli flags:
- `--listen-addresses` now can take up to two values
- `--port` will apply to ipv4 or ipv6 if only one listening address is given. If two listening addresses are given it will apply only to Ipv4.
- `--port6` New flag required when listening over ipv4 and ipv6 that applies exclusively to Ipv6.
- `--discovery-port` will now apply to ipv4 and ipv6 if only one listening address is given.
- `--discovery-port6` New flag to configure the individual udp port of ipv6 if listening over both ipv4 and ipv6.
- `--enr-udp-port` Updated docs to specify that it only applies to ipv4. This is an old behaviour.
- `--enr-udp6-port` Added to configure the enr udp6 field.
- `--enr-tcp-port` Updated docs to specify that it only applies to ipv4. This is an old behaviour.
- `--enr-tcp6-port` Added to configure the enr tcp6 field.
- `--enr-addresses` now can take two values.
- `--enr-match` updated behaviour.
- Common:
- rename `unused_port` functions to specify that they are over ipv4.
- add functions to get unused ports over ipv6.
- Testing binaries
- Updated code to reflect network config changes and unused_port changes.
## Additional Info
TODOs:
- use two sockets in discovery. I'll get back to this and it's on https://github.com/sigp/discv5/pull/160
- lcli allow listening over two sockets in generate_bootnodes_enr
- add at least one smoke flag for ipv6 (I have tested this and works for me)
- update the book
* wip
* fix router
* arc the byroot responses we send
* add placeholder for blob verification
* respond to blobs by range and blobs by root request in the most horrible and gross way ever
* everything in sync is now unimplemented
* fix compiation issues
* http_pi change is very small, just add it
* remove ctrl-c ctrl-v's docs
## Issue Addressed
Cleaner resolution for #4006
## Proposed Changes
We are currently subscribing to core topics of new forks way before the actual fork since we had just a single `CORE_TOPICS` array. This PR separates the core topics for every fork and subscribes to only required topics based on the current fork.
Also adds logic for subscribing to the core topics of a new fork only 2 slots before the fork happens.
2 slots is to give enough time for the gossip meshes to form.
Currently doesn't add logic to remove topics from older forks in new forks. For e.g. in the coupled 4844 world, we had to remove the `BeaconBlock` topic in favour of `BeaconBlocksAndBlobsSidecar` at the 4844 fork. It should be easy enough to add though. Not adding it because I'm assuming that #4019 will get merged before this PR and we won't require any deletion logic. Happy to add it regardless though.
## Issue Addressed
Cleans up all the remnants of 4844 in capella. This makes sure when 4844 is reviewed there is nothing we are missing because it got included here
## Proposed Changes
drop a bomb on every 4844 thing
## Additional Info
Merge process I did (locally) is as follows:
- squash merge to produce one commit
- in new branch off unstable with the squashed commit create a `git revert HEAD` commit
- merge that new branch onto 4844 with `--strategy ours`
- compare local 4844 to remote 4844 and make sure the diff is empty
- enjoy
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## Issue Addressed
Windows tests for subscription and unsubscriptions fail in CI sporadically. We usually ignore this failures, so this PR aims to help reduce the failure noise. Associated issue is https://github.com/sigp/lighthouse/issues/3960
## 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
* Add first efforts at broadcast
* Tidy
* Move broadcast code to client
* Progress with broadcast impl
* Rename to address change
* Fix compile errors
* Use `while` loop
* Tidy
* Flip broadcast condition
* Switch to forgetting individual indices
* Always broadcast when the node starts
* Refactor into two functions
* Add testing
* Add another test
* Tidy, add more testing
* Tidy
* Add test, rename enum
* Rename enum again
* Tidy
* Break loop early
* Add V15 schema migration
* Bump schema version
* Progress with migration
* Update beacon_node/client/src/address_change_broadcast.rs
Co-authored-by: Michael Sproul <micsproul@gmail.com>
* Fix typo in function name
---------
Co-authored-by: Michael Sproul <micsproul@gmail.com>
Currently there is a race between receiving blocks and receiving light client optimistic updates (in unstable), which results in processing errors. This is a continuation of PR #3693 and seeks to progress on issue #3651
Add the parent_root to ReprocessQueueMessage::BlockImported so we can remove blocks from queue when a block arrives that has the same parent root. We use the parent root as opposed to the block_root because the LightClientOptimisticUpdate does not contain the block_root.
If light_client_optimistic_update.attested_header.canonical_root() != head_block.message().parent_root() then we queue the update. Otherwise we process immediately.
michaelsproul came up with this idea.
The code was heavily based off of the attestation reprocessing.
I have not properly tested this to see if it works as intended.
* Import BLS to execution changes before Capella
* Test for BLS to execution change HTTP API
* Pack BLS to execution changes in LIFO order
* Remove unused var
* Clippy
We recently ran a large-block experiment on the testnet and plan to do a further experiment on mainnet.
Although the metrics recovered from lighthouse nodes were quite useful, I think we could do with greater resolution in the block delay metrics and get some specific values for each block (currently these can be lost to large exponential histogram buckets).
This PR increases the resolution of the block delay histogram buckets, but also introduces a new metric which records the last block delay. Depending on the polling resolution of the metric server, we can lose some block delay information, however it will always give us a specific value and we will not lose exact data based on poor resolution histogram buckets.
## Issue Addressed
Currently there is a race between receiving blocks and receiving light client optimistic updates (in unstable), which results in processing errors. This is a continuation of PR #3693 and seeks to progress on issue #3651
## Proposed Changes
Add the parent_root to ReprocessQueueMessage::BlockImported so we can remove blocks from queue when a block arrives that has the same parent root. We use the parent root as opposed to the block_root because the LightClientOptimisticUpdate does not contain the block_root.
If light_client_optimistic_update.attested_header.canonical_root() != head_block.message().parent_root() then we queue the update. Otherwise we process immediately.
## Additional Info
michaelsproul came up with this idea.
The code was heavily based off of the attestation reprocessing.
I have not properly tested this to see if it works as intended.
* Import BLS to execution changes before Capella
* Test for BLS to execution change HTTP API
* Pack BLS to execution changes in LIFO order
* Remove unused var
* Clippy
We recently ran a large-block experiment on the testnet and plan to do a further experiment on mainnet.
Although the metrics recovered from lighthouse nodes were quite useful, I think we could do with greater resolution in the block delay metrics and get some specific values for each block (currently these can be lost to large exponential histogram buckets).
This PR increases the resolution of the block delay histogram buckets, but also introduces a new metric which records the last block delay. Depending on the polling resolution of the metric server, we can lose some block delay information, however it will always give us a specific value and we will not lose exact data based on poor resolution histogram buckets.
## Issue Addressed
NA
## Proposed Changes
Myself and others (#3678) have observed that when running with lots of validators (e.g., 1000s) the cardinality is too much for Prometheus. I've seen Prometheus instances just grind to a halt when we turn the validator monitor on for our testnet validators (we have 10,000s of Goerli validators). Additionally, the debug log volume can get very high with one log per validator, per attestation.
To address this, the `bn --validator-monitor-individual-tracking-threshold <INTEGER>` flag has been added to *disable* per-validator (i.e., non-aggregated) metrics/logging once the validator monitor exceeds the threshold of validators. The default value is `64`, which is a finger-to-the-wind value. I don't actually know the value at which Prometheus starts to become overwhelmed, but I've seen it work with ~64 validators and I've seen it *not* work with 1000s of validators. A default of `64` seems like it will result in a breaking change to users who are running millions of dollars worth of validators whilst resulting in a no-op for low-validator-count users. I'm open to changing this number, though.
Additionally, this PR starts collecting aggregated Prometheus metrics (e.g., total count of head hits across all validators), so that high-validator-count validators still have some interesting metrics. We already had logging for aggregated values, so nothing has been added there.
I've opted to make this a breaking change since it can be rather damaging to your Prometheus instance to accidentally enable the validator monitor with large numbers of validators. I've crashed a Prometheus instance myself and had a report from another user who's done the same thing.
## Additional Info
NA
## Breaking Changes Note
A new label has been added to the validator monitor Prometheus metrics: `total`. This label tracks the aggregated metrics of all validators in the validator monitor (as opposed to each validator being tracking individually using its pubkey as the label).
Additionally, a new flag has been added to the Beacon Node: `--validator-monitor-individual-tracking-threshold`. The default value is `64`, which means that when the validator monitor is tracking more than 64 validators then it will stop tracking per-validator metrics and only track the `all_validators` metric. It will also stop logging per-validator logs and only emit aggregated logs (the exception being that exit and slashing logs are always emitted).
These changes were introduced in #3728 to address issues with untenable Prometheus cardinality and log volume when using the validator monitor with high validator counts (e.g., 1000s of validators). Users with less than 65 validators will see no change in behavior (apart from the added `all_validators` metric). Users with more than 65 validators who wish to maintain the previous behavior can set something like `--validator-monitor-individual-tracking-threshold 999999`.
## 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.
