## 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
This PR enables the user to adjust the shuffling cache size.
This is useful for some HTTP API requests which require re-computing old shufflings. This PR currently optimizes the
beacon/states/{state_id}/committees HTTP API by first checking the cache before re-building shuffling.
If the shuffling is set to a non-default value, then the HTTP API request will also fill the cache when as it constructs new shufflings.
If the CLI flag is not present or the value is set to the default of 16 the default behaviour is observed.
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
Currently Lighthouse will remain uncontactable if users port forward a port that is not the same as the one they are listening on.
For example, if Lighthouse runs with port 9000 TCP/UDP locally but a router is configured to pass 9010 externally to the lighthouse node on 9000, other nodes on the network will not be able to reach the lighthouse node.
This occurs because Lighthouse does not update its ENR TCP port on external socket discovery. The intention was always that users should use `--enr-tcp-port` to customise this, but this is non-intuitive.
The difficulty arises because we have no discovery mechanism to find our external TCP port. If we discovery a new external UDP port, we must guess what our external TCP port might be. This PR assumes the external TCP port is the same as the external UDP port (which may not be the case) and thus updates the TCP port along with the UDP port if the `--enr-tcp-port` flag is not set.
Along with this PR, will be added documentation to the Lighthouse book so users can correctly understand and configure their ENR to maximize Lighthouse's connectivity.
This relies on https://github.com/sigp/discv5/pull/166 and we should wait for a new release in discv5 before adding this PR.
If a node is also a bootnode it can try to add itself to its own local routing table which will emit an error.
The error is entirely harmless but we would prefer to avoid emitting the error.
This PR does not attempt to add a boot node ENR if that ENR corresponds to our local peer-id/node-id.
## Issue Addressed
Resolves#4061
## Proposed Changes
Adds a message to tell users to check their EE.
## Additional Info
I really struggled to come up with something succinct and complete, so I'm totally open to feedback.
## Issue Addressed
NA
## Proposed Changes
When producing a block from a builder, there are two points where we could consider the block "broadcast":
1. When the blinded block is published to the builder.
2. When the un-blinded block is published to the P2P network (this is always *after* the previous step).
Our logging for late block broadcasts was using (2) for builder-blocks, which was creating a lot of false-positive logs. This is because the builder publishes the block on the P2P network themselves before returning it to us and we perform (2). For clarity, the logs were false-positives because we claim that the block was published late by us when it was actually published earlier by the builder.
This PR changes our logging behavior so we do our logging at (1) instead. It also updates our metrics for block broadcast to distinguish between local and builder blocks. I believe the metrics change will be natively compatible with existing Grafana dashboards.
## Additional Info
One could argue that the builder *should* return the block to us faster, however that's not the case. I think it's more important that we don't desensitize users with false-positives.
## 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.
## 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 a complete match for `Protocol` here.
- The incomplete match was causing us not to append context bytes to the light client protocols
- This is the relevant part of the spec and it looks like context bytes are defined https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/p2p-interface.md#getlightclientbootstrap
Disclaimer: I have no idea if people are using it but it shouldn't have been working so not sure why it wasn't caught
Co-authored-by: realbigsean <seananderson33@gmail.com>
## Issue Addressed
In #4027 I forgot to add the `parent_block_number` to the payload attributes SSE.
## Proposed Changes
Compute the parent block number while computing the pre-payload attributes. Pass it on to the SSE stream.
## Additional Info
Not essential for v3.5.1 as I suspect most builders don't need the `parent_block_root`. I would like to use it for my dummy no-op builder however.
## 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
## Proposed Changes
The current `/lighthouse/nat` implementation checks for _zero_ address updated messages, when it should check for a _non-zero_ number. This was spotted while debugging an issue on Discord where a user's ports weren't forwarded but `/lighthouse/nat` was still returning `true`.
## Issue Addressed
#3435
## Proposed Changes
Fire a warning with the path of JWT to be created when the path given by --execution-jwt is not found
Currently, the same error is logged if the jwt is found but doesn't match the execution client's jwt, and if no jwt was found at the given path. This makes it very hard to tell if you accidentally typed the wrong path, as a new jwt is created silently that won't match the execution client's jwt. So instead, it will now fire a warning stating that a jwt is being generated at the given path.
## Additional Info
In the future, it may be smarter to handle this case by adding an InvalidJWTPath member to the Error enum in lib.rs or auth.rs
that can be handled during upcheck()
This is my first PR and first project with rust. so thanks to anyone who looks at this for their patience and help!
Co-authored-by: Sebastian Richel <47844429+sebastianrich18@users.noreply.github.com>
## Proposed Changes
Two tiny updates to satisfy Clippy 1.68
Plus refactoring of the `http_api` into less complex types so the compiler can chew and digest them more easily.
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
## Issue Addressed
#4040
## Proposed Changes
- Add the `always_prefer_builder_payload` field to `Config` in `beacon_node/client/src/config.rs`.
- Add that same field to `Inner` in `beacon_node/execution_layer/src/lib.rs`
- Modify the logic for picking the payload in `beacon_node/execution_layer/src/lib.rs`
- Add the `always-prefer-builder-payload` flag to the beacon node CLI
- Test the new flags in `lighthouse/tests/beacon_node.rs`
Co-authored-by: Paul Hauner <paul@paulhauner.com>
## Issue Addressed
Closes#3896Closes#3998Closes#3700
## Proposed Changes
- Optimise the calculation of withdrawals for payload attributes by avoiding state clones, avoiding unnecessary state advances and reading from the snapshot cache if possible.
- Use the execution layer's payload attributes cache to avoid re-calculating payload attributes. I actually implemented a new LRU cache just for withdrawals but it had the exact same key and most of the same data as the existing payload attributes cache, so I deleted it.
- Add a new SSE event that fires when payloadAttributes are calculated. This is useful for block builders, a la https://github.com/ethereum/beacon-APIs/issues/244.
- Add a new CLI flag `--always-prepare-payload` which forces payload attributes to be sent with every fcU regardless of connected proposers. This is intended for use by builders/relays.
For maximum effect, the flags I've been using to run Lighthouse in "payload builder mode" are:
```
--always-prepare-payload \
--prepare-payload-lookahead 12000 \
--suggested-fee-recipient 0x0000000000000000000000000000000000000000
```
The fee recipient is required so Lighthouse has something to pack in the payload attributes (it can be ignored by the builder). The lookahead causes fcU to be sent at the start of every slot rather than at 8s. As usual, fcU will also be sent after each change of head block. I think this combination is sufficient for builders to build on all viable heads. Often there will be two fcU (and two payload attributes) sent for the same slot: one sent at the start of the slot with the head from `n - 1` as the parent, and one sent after the block arrives with `n` as the parent.
Example usage of the new event stream:
```bash
curl -N "http://localhost:5052/eth/v1/events?topics=payload_attributes"
```
## Additional Info
- [x] Tests added by updating the proposer re-org tests. This has the benefit of testing the proposer re-org code paths with withdrawals too, confirming that the new changes don't interact poorly.
- [ ] Benchmarking with `blockdreamer` on devnet-7 showed promising results but I'm yet to do a comparison to `unstable`.
Co-authored-by: Michael Sproul <micsproul@gmail.com>
## Issue Addressed
NA
## Proposed Changes
As discovered in #4034, Lighthouse is not accepting `latest_valid_hash == None` in an `INVALID` response to `newPayload`. The `null`/`None` response *was* illegal at one point, however it was added in https://github.com/ethereum/execution-apis/pull/254.
This PR brings Lighthouse in line with the standard and should fix the root cause of what #4034 patched around.
## Additional Info
NA
## 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
NA
## Proposed Changes
Adds two new `DEBG` logs to the HTTP API:
1. As soon as we are requested to produce a block.
2. As soon as a signed block is received.
In #3858 we added some very helpful logs to the VC so we could see when things are happening with block proposals in the VC. After doing some more debugging, I found that I can tell when the VC is sending a block but I *can't* tell the time that the BN receives it (I can only get the time after the BN has started doing some work with the block). Knowing when the VC published and as soon as the BN receives is useful for determining the delays introduced by network latency (and some other things like JSON decoding, etc).
## Additional Info
NA
This fixes issues with certain metrics scrapers, which might error if the content-type is not correctly set.
## Issue Addressed
Fixes https://github.com/sigp/lighthouse/issues/3437
## Proposed Changes
Simply set header: `Content-Type: text/plain` on metrics server response. Seems like the errored branch does this correctly already.
## Additional Info
This is needed also to enable influx-db metric scraping which work very nicely with Geth.
## Proposed Changes
Allowing compiling without MDBX by running:
```bash
CARGO_INSTALL_EXTRA_FLAGS="--no-default-features" make
```
The reasons to do this are several:
- Save compilation time if the slasher won't be used
- Work around compilation errors in slasher backend dependencies (our pinned version of MDBX is currently not compiling on FreeBSD with certain compiler versions).
## Additional Info
When I opened this PR we were using resolver v1 which [doesn't disable default features in dependencies](https://doc.rust-lang.org/cargo/reference/features.html#resolver-version-2-command-line-flags), and `mdbx` is default for the `slasher` crate. Even after the resolver got changed to v2 in #3697 compiling with `--no-default-features` _still_ wasn't turning off the slasher crate's default features, so I added `default-features = false` in all the places we depend on it.
Co-authored-by: Michael Sproul <micsproul@gmail.com>
## Issue Addressed
NA
## Proposed Changes
- Bump versions
## Sepolia Capella Upgrade
This release will enable the Capella fork on Sepolia. We are planning to publish this release on the 23rd of Feb 2023.
Users who can build from source and wish to do pre-release testing can use this branch.
## Additional Info
- [ ] Requires further testing
This is a correction to #3757.
The correction registers a peer that is being disconnected in the local peer manager db to ensure we are tracking the correct state.
## Issue Addressed
#3804
## Proposed Changes
- Add `total_balance` to the validator monitor and adjust the number of historical epochs which are cached.
- Allow certain values in the cache to be served out via the HTTP API without requiring a state read.
## Usage
```
curl -X POST "http://localhost:5052/lighthouse/ui/validator_info" -d '{"indices": [0]}' -H "Content-Type: application/json" | jq
```
```
{
"data": {
"validators": {
"0": {
"info": [
{
"epoch": 172981,
"total_balance": 36566388519
},
...
{
"epoch": 172990,
"total_balance": 36566496513
}
]
},
"1": {
"info": [
{
"epoch": 172981,
"total_balance": 36355797968
},
...
{
"epoch": 172990,
"total_balance": 36355905962
}
]
}
}
}
}
```
## Additional Info
This requires no historical states to operate which mean it will still function on the freshly checkpoint synced node, however because of this, the values will populate each epoch (up to a maximum of 10 entries).
Another benefit of this method, is that we can easily cache any other values which would normally require a state read and serve them via the same endpoint. However, we would need be cautious about not overly increasing block processing time by caching values from complex computations.
This also caches some of the validator metrics directly, rather than pulling them from the Prometheus metrics when the API is called. This means when the validator count exceeds the individual monitor threshold, the cached values will still be available.
Co-authored-by: Paul Hauner <paul@paulhauner.com>
* Remove CapellaReadiness::NotSynced
Some EEs have a habit of flipping between synced/not-synced, which causes some
spurious "Not read for the merge" messages back before the merge. For the
merge, if the EE wasn't synced the CE simple wouldn't go through the transition
(due to optimistic sync stuff). However, we don't have that hard requirement
for Capella; the CE will go through the fork and just wait for the EE to catch
up. I think that removing `NotSynced` here will avoid false-positives on the
"Not ready logs..". We'll be creating other WARN/ERRO logs if the EE isn't
synced, anyway.
* Change some Capella readiness logging
There's two changes here:
1. Shorten the log messages, for readability.
2. Change the hints.
Connecting a Capella-ready LH to a non-Capella-ready EE gives this log:
```
WARN Not ready for Capella info: The execution endpoint does not appear to support the required engine api methods for Capella: Required Methods Unsupported: engine_getPayloadV2 engine_forkchoiceUpdatedV2 engine_newPayloadV2, service: slot_notifier
```
This variant of error doesn't get a "try updating" style hint, when it's the
one that needs it. This is because we detect the method-not-found reponse from
the EE and return default capabilities, rather than indicating that the request
fails. I think it's fair to say that an EE upgrade is required whenever it
doesn't provide the required methods.
I changed the `ExchangeCapabilitiesFailed` message since that can only happen
when the EE fails to respond with anything other than success or not-found.
## 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
On heavily crowded networks, we are seeing many attempted connections to our node every second.
Often these connections come from peers that have just been disconnected. This can be for a number of reasons including:
- We have deemed them to be not as useful as other peers
- They have performed poorly
- They have dropped the connection with us
- The connection was spontaneously lost
- They were randomly removed because we have too many peers
In all of these cases, if we have reached or exceeded our target peer limit, there is no desire to accept new connections immediately after the disconnect from these peers. In fact, it often costs us resources to handle the established connections and defeats some of the logic of dropping them in the first place.
This PR adds a timeout, that prevents recently disconnected peers from reconnecting to us.
Technically we implement a ban at the swarm layer to prevent immediate re connections for at least 10 minutes. I decided to keep this light, and use a time-based LRUCache which only gets updated during the peer manager heartbeat to prevent added stress of polling a delay map for what could be a large number of peers.
This cache is bounded in time. An extra space bound could be added should people consider this a risk.
Co-authored-by: Diva M <divma@protonmail.com>
## Issue Addressed
Fix a bug introduced by #3696. The bug is not expected to occur frequently, so releasing this PR is non-urgent.
## Proposed Changes
* Add a variant to `StoreOp` that allows a raw KV operation to be passed around.
* Return to using `self.store.do_atomically` rather than `self.store.hot_db.do_atomically`. This streamlines the write back into a single call and makes our auto-revert work again.
* Prevent `import_block_update_shuffling_cache` from failing block import. This is an outstanding bug from before v3.4.0 which may have contributed to some random unexplained database corruption.
## Additional Info
In #3696 I split the database write into two calls, one to convert the `StoreOp`s to `KeyValueStoreOp`s and one to write them. This had the unfortunate side-effect of damaging our atomicity guarantees in case of a write error. If the first call failed, we would be left with the block in fork choice but not on-disk (or the snapshot cache), which would prevent us from processing any descendant blocks. On `unstable` the first call is very unlikely to fail unless the disk is full, but on `tree-states` the conversion is more involved and a user reported database corruption after it failed in a way that should have been recoverable.
Additionally, as @emhane observed, #3696 also inadvertently removed the import of the new block into the block cache. Although this seems like it could have negatively impacted performance, there are several mitigating factors:
- For regular block processing we should almost always load the parent block (and state) from the snapshot cache.
- We often load blinded blocks, which bypass the block cache anyway.
- Metrics show no noticeable increase in the block cache miss rate with v3.4.0.
However, I expect the block cache _will_ be useful again in `tree-states`, so it is restored to use by this PR.
## 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
## Issue Addressed
NA
## Description
We were missing an edge case when checking to see if a block is a descendant of the finalized checkpoint. This edge case is described for one of the tests in this PR:
a119edc739/consensus/proto_array/src/proto_array_fork_choice.rs (L1018-L1047)
This bug presented itself in the following mainnet log:
```
Jan 26 15:12:42.841 ERRO Unable to validate attestation error: MissingBeaconState(0x7c30cb80ec3d4ec624133abfa70e4c6cfecfca456bfbbbff3393e14e5b20bf25), peer_id: 16Uiu2HAm8RPRciXJYtYc5c3qtCRdrZwkHn2BXN3XP1nSi1gxHYit, type: "unaggregated", slot: Slot(5660161), beacon_block_root: 0x4a45e59da7cb9487f4836c83bdd1b741b4f31c67010c7ae343fa6771b3330489
```
Here the BN is rejecting an attestation because of a "missing beacon state". Whilst it was correct to reject the attestation, it should have rejected it because it attests to a block that conflicts with finality rather than claiming that the database is inconsistent.
The block that this attestation points to (`0x4a45`) is block `C` in the above diagram. It is a non-canonical block in the first slot of an epoch that conflicts with the finalized checkpoint. Due to our lazy pruning of proto array, `0x4a45` was still present in proto-array. Our missed edge-case in [`ForkChoice::is_descendant_of_finalized`](38514c07f2/consensus/fork_choice/src/fork_choice.rs (L1375-L1379)) would have indicated to us that the block is a descendant of the finalized block. Therefore, we would have accepted the attestation thinking that it attests to a descendant of the finalized *checkpoint*.
Since we didn't have the shuffling for this erroneously processed block, we attempted to read its state from the database. This failed because we prune states from the database by keeping track of the tips of the chain and iterating back until we find a finalized block. This would have deleted `C` from the database, hence the `MissingBeaconState` error.
