`news` has a few open issues that are not present in `nim-websock`:
1. There is a 1 second delay between each MB of sent data.
2. Cancelling an ongoing `send` makes the entire WebSocket unusable.
3. Control packets do not have priority over ongoing message frames.
Using `news`, there are quite a few of these messages in Geth:
```
Previously seen beacon client is offline. Please ensure it is
operational to follow the chain!
```
It may take quite some time to reconnect when this happens.
Using `nim-websock`, this message still occurs because `eth1_monitor`
reconnects the EL connection when no new blocks occurred for 5 minutes,
but reconnecting is quick and the message is rarer.
The sync protocol does not distinguish between:
- All requested slots are empty
- Peer does not have data available about requested range
Therefore, we treat EOF for `beacon_blocks_by_range` and for
`beacon_blocks_by_range` as valid responses, as if the entire epoch
really contained no single block for any slot. Once a followup response
provides new blocks, we detect that some blocks were missing and rewind.
During backfill, we also request the known-to-exist `backfill.slot`,
so we can actually detect whether an epoch really does not have blocks
or whether a response is incomplete (`PeerScoreNoBlocks`).
When the BN-embedded LC makes sync progress, pass the corresponding
execution block hash to the EL via `engine_forkchoiceUpdatedV1`.
This allows the EL to sync to wall slot while the chain DAG is behind.
Renamed `--light-client` to `--sync-light-client` for clarity, and
`--light-client-trusted-block-root` to `--trusted-block-root` for
consistency with `nimbus_light_client`.
Note that this does not work well in practice at this time:
- Geth sticks to the optimistic sync:
"Ignoring payload while snap syncing" (when passing the LC head)
"Forkchoice requested unknown head" (when updating to LC head)
- Nethermind syncs to LC head but does not report ancestors as VALID,
so the main forward sync is still stuck in optimistic mode:
"Pre-pivot block, ignored and returned Syncing"
To aid EL client teams in fixing those issues, having this available
as a hidden option is still useful.
When calling `newPayload` on a >1MB payload (can happen post-merge),
`news` splits up that payload into 1MB chunks. The chunks are each sent
individually, though, with `await` in-between. This means that when we
send concurrent `forkChoiceUpdated` calls, that those may end up getting
in-between the `newPayload` chunks, leading to invalid data being sent.
The EL then returns an error message with a `null` `id` entry (as it
could not read the request `id` due to the mangling) and disconnects.
A PR has been submitted to fix this in `news`, and merged into `status`
branch early as this fix is critical for reliable post-merge operation:
https://github.com/Tormund/news/pull/22
When issuing an engine API call while the EL is disconnected, a `nil`
pointer is dereferenced. Fixed by correctly initializing futures.
```
Traceback (most recent call last, using override)
vendor/nim-libp2p/libp2p/protocols/pubsub/pubsub.nim(890) main
beacon_chain/nimbus_beacon_node.nim(2139) main
beacon_chain/nimbus_beacon_node.nim(0) handleStartUpCmd
beacon_chain/nimbus_beacon_node.nim(0) doRunBeaconNode
beacon_chain/nimbus_beacon_node.nim(0) start
beacon_chain/nimbus_beacon_node.nim(1589) run
vendor/nimbus-build-system/vendor/Nim/lib/system/iterators_1.nim(107) poll
vendor/nim-chronos/chronos/asyncfutures2.nim(365) futureContinue
beacon_chain/consensus_object_pools/consensus_manager.nim(297) updateHeadWithExecution
vendor/nim-chronos/chronos/asyncmacro2.nim(213) runProposalForkchoiceUpdated
vendor/nim-chronos/chronos/asyncfutures2.nim(365) futureContinue
beacon_chain/consensus_object_pools/consensus_manager.nim(259) runProposalForkchoiceUpdated
beacon_chain/eth1/eth1_monitor.nim(0) forkchoiceUpdated
vendor/nim-chronos/chronos/asyncfutures2.nim(219) complete
vendor/nim-chronos/chronos/asyncfutures2.nim(149) cancelled
vendor/nimbus-build-system/vendor/Nim/lib/system/excpt.nim(610) signalHandler
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
```
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.
When the EL fails to respond to `newPayload`, e.g., because connection
to the EL got interrupted, or due to misconfiguration, optimistic blocks
cannot be imported according to spec. This condition is treated the same
as if the peer returned a block with missing parent which gets the block
out of our processing queue, but can have nasty side effects.
For example, if sync manager asks for validation of a block known to be
in the finalized range, if it receives a `MissingParent` verdict, the
peer is immediately removed from the peer pool.
```
DBG 2022-08-24 11:45:26.874+02:00 newPayload: inserting block into execution engine parentHash=e4ca7424 blockHash=36cdc198 stateRoot=cf3902c1 receiptsRoot=56e81f17 prevRandao=0b49a172 blockNumber=1518089 gasLimit=30000000 gasUsed=0 timestamp=1657980396 extraDataLen=0 baseFeePerGas=7 numTransactions=0
ERR 2022-08-24 11:45:26.875+02:00 newPayload failed msg="Transport is not initialised (missing a call to connect?)"
DBG 2022-08-24 11:45:26.875+02:00 Block pool rejected peer's response topics="syncman" request=187232:32@1475 peer=16U*MsCJdx direction=forward blocks_map=xxxxxxxxxxxxxxxxxxxxxxxxxxxx.xxx blocks_count=31 ok=false unviable=false missing_parent=true sync_ident=main
ERR 2022-08-24 11:45:26.875+02:00 Unexpected missing parent at finalized epoch slot topics="syncman" request=187232:32@1475 peer=16U*MsCJdx direction=forward rewind_to_slot=187232 blocks_count=31 blocks_map=xxxxxxxxxxxxxxxxxxxxxxxxxxxx.xxx sync_ident=main
DBG 2022-08-24 11:45:26.875+02:00 Peer was removed from PeerPool due to low score topics="beacnde" peer=16U*MsCJdx peer_score=-1000 score_low_limit=0 score_high_limit=1000
DBG 2022-08-24 11:45:26.875+02:00 Lost connection to peer topics="networking" peer=16U*MsCJdx connections=0
```
By delaying issuing a verdict until the EL connection is restored and
`newPayload` successfully ran, the problem should be fixed. This also
induces back pressure to the sync manager by stopping download of new
blocks (or re-downloading the same block over and over again).
* Harden block proposal against expired slashings/exits
When a message is signed in a phase0 domain, it can no longer be
validated under bellatrix due to the correct fork no longer being
available in the `BeaconState`.
To ensure that all slashing/exits are still valid, in this PR we re-run
the checks in the state that we're proposing for, thus hardening against
both signatures and other changes in the state that might have
invalidated the message.
* fix same message added multiple times
in case of attestation slashing of multiple validators in one go
Etan Kissling
tersec
Jacek Sieka
Miran
Tanguy
omahs
Zahary Karadjov
dependabot[bot]