# beacon_chain # Copyright (c) 2022 Status Research & Development GmbH # Licensed and distributed under either of # * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT). # * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0). # at your option. This file may not be copied, modified, or distributed except according to those terms. {.push raises: [Defect].} # This implements the pre-release proposal of the libp2p based light client sync # protocol. See https://github.com/ethereum/consensus-specs/pull/2802 import # Status libraries stew/[bitops2, objects], chronos, # Beacon chain internals ../spec/datatypes/[phase0, altair, bellatrix], "."/[block_pools_types, blockchain_dag] logScope: topics = "chaindag" type HashedBeaconStateWithSyncCommittee = bellatrix.HashedBeaconState | altair.HashedBeaconState TrustedSignedBeaconBlockWithSyncAggregate = bellatrix.TrustedSignedBeaconBlock | altair.TrustedSignedBeaconBlock template nextEpochBoundarySlot(slot: Slot): Slot = ## Compute the first possible epoch boundary state slot of a `Checkpoint` ## referring to a block at given slot. (slot + (SLOTS_PER_EPOCH - 1)).epoch.start_slot func computeEarliestLightClientSlot(dag: ChainDAGRef): Slot = ## Compute the earliest slot for which light client data is retained. let minSupportedSlot = max( dag.cfg.ALTAIR_FORK_EPOCH.start_slot, dag.lcDataStore.cache.importTailSlot) currentSlot = getStateField(dag.headState, slot) if currentSlot < minSupportedSlot: return minSupportedSlot let MIN_EPOCHS_FOR_BLOCK_REQUESTS = dag.cfg.MIN_VALIDATOR_WITHDRAWABILITY_DELAY + dag.cfg.CHURN_LIMIT_QUOTIENT div 2 MIN_SLOTS_FOR_BLOCK_REQUESTS = MIN_EPOCHS_FOR_BLOCK_REQUESTS * SLOTS_PER_EPOCH if currentSlot - minSupportedSlot < MIN_SLOTS_FOR_BLOCK_REQUESTS: return minSupportedSlot let earliestSlot = currentSlot - MIN_SLOTS_FOR_BLOCK_REQUESTS max(earliestSlot.sync_committee_period.start_slot, minSupportedSlot) proc updateExistingState( dag: ChainDAGRef, state: var ForkedHashedBeaconState, bsi: BlockSlotId, save: bool, cache: var StateCache): bool = ## Wrapper around `updateState` for states expected to exist. let ok = dag.updateState(state, bsi, save, cache) if not ok: error "State failed to load unexpectedly", bsi, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags ok template withUpdatedExistingState( dag: ChainDAGRef, stateParam: var ForkedHashedBeaconState, bsiParam: BlockSlotId, okBody: untyped, failureBody: untyped): untyped = ## Wrapper around `withUpdatedState` for states expected to exist. block: let bsi = bsiParam dag.withUpdatedState(stateParam, bsiParam) do: okBody do: error "State failed to load unexpectedly", bsi, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags failureBody proc getExistingBlockIdAtSlot(dag: ChainDAGRef, slot: Slot): Opt[BlockSlotId] = ## Wrapper around `getBlockIdAtSlot` for blocks expected to exist. let bsi = dag.getBlockIdAtSlot(slot) if bsi.isErr: error "Block failed to load unexpectedly", slot, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags bsi proc existingParent(dag: ChainDAGRef, bid: BlockId): Opt[BlockId] = ## Wrapper around `parent` for parents known to exist. let parent = dag.parent(bid) if parent.isErr: error "Parent failed to load unexpectedly", bid, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags parent proc getExistingForkedBlock( dag: ChainDAGRef, bid: BlockId): Opt[ForkedTrustedSignedBeaconBlock] = ## Wrapper around `getForkedBlock` for blocks expected to exist. let bdata = dag.getForkedBlock(bid) if bdata.isErr: error "Block failed to load unexpectedly", bid, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags bdata proc existingCurrentSyncCommitteeForPeriod( dag: ChainDAGRef, tmpState: var ForkedHashedBeaconState, period: SyncCommitteePeriod): Opt[SyncCommittee] = ## Wrapper around `currentSyncCommitteeForPeriod` for states known to exist. let syncCommittee = dag.currentSyncCommitteeForPeriod(tmpState, period) if syncCommittee.isErr: error "Current sync committee failed to load unexpectedly", period, tail = dag.tail.slot doAssert verifyFinalization notin dag.updateFlags syncCommittee template syncCommitteeRoot( state: HashedBeaconStateWithSyncCommittee): Eth2Digest = ## Compute a root to uniquely identify `current_sync_committee` and ## `next_sync_committee`. withEth2Hash: h.update state.data.current_sync_committee.hash_tree_root().data h.update state.data.next_sync_committee.hash_tree_root().data proc syncCommitteeRootForPeriod( dag: ChainDAGRef, tmpState: var ForkedHashedBeaconState, period: SyncCommitteePeriod): Opt[Eth2Digest] = ## Compute a root to uniquely identify `current_sync_committee` and ## `next_sync_committee` for a given sync committee period. ## For non-finalized periods, follow the chain as selected by fork choice. let lowSlot = max(dag.tail.slot, dag.cfg.ALTAIR_FORK_EPOCH.start_slot) if period < lowSlot.sync_committee_period: return err() let periodStartSlot = period.start_slot syncCommitteeSlot = max(periodStartSlot, lowSlot) bsi = ? dag.getExistingBlockIdAtSlot(syncCommitteeSlot) dag.withUpdatedExistingState(tmpState, bsi) do: withState(state): when stateFork >= BeaconStateFork.Altair: ok state.syncCommitteeRoot else: raiseAssert "Unreachable" do: err() proc getLightClientData( dag: ChainDAGRef, bid: BlockId): CachedLightClientData = ## Fetch cached light client data about a given block. ## Data must be cached (`cacheLightClientData`) before calling this function. try: dag.lcDataStore.cache.data[bid] except KeyError: raiseAssert "Unreachable" proc cacheLightClientData( dag: ChainDAGRef, state: HashedBeaconStateWithSyncCommittee, bid: BlockId) = ## Cache data for a given block and its post-state to speed up creating future ## `LightClientUpdate` and `LightClientBootstrap` instances that refer to this ## block and state. let cachedData = CachedLightClientData( current_sync_committee_branch: state.data.build_proof(altair.CURRENT_SYNC_COMMITTEE_INDEX).get, next_sync_committee_branch: state.data.build_proof(altair.NEXT_SYNC_COMMITTEE_INDEX).get, finalized_slot: state.data.finalized_checkpoint.epoch.start_slot, finality_branch: state.data.build_proof(altair.FINALIZED_ROOT_INDEX).get) if dag.lcDataStore.cache.data.hasKeyOrPut(bid, cachedData): doAssert false, "Redundant `cacheLightClientData` call" proc deleteLightClientData*(dag: ChainDAGRef, bid: BlockId) = ## Delete cached light client data for a given block. This needs to be called ## when a block becomes unreachable due to finalization of a different fork. if dag.lcDataStore.importMode == LightClientDataImportMode.None: return dag.lcDataStore.cache.data.del bid func handleUnexpectedLightClientError(dag: ChainDAGRef, buggedSlot: Slot) = ## If there is an unexpected error, adjust `importTailSlot` to keep track of ## section for which complete light client data is available, and to avoid ## failed lookups of cached light client data. doAssert verifyFinalization notin dag.updateFlags if buggedSlot >= dag.lcDataStore.cache.importTailSlot: dag.lcDataStore.cache.importTailSlot = buggedSlot + 1 template lazy_header(name: untyped): untyped {.dirty.} = ## `createLightClientUpdates` helper to lazily load a known block header. var `name _ ptr`: ptr[BeaconBlockHeader] `name _ ok` = true template `assign _ name`(target: var BeaconBlockHeader, bid: BlockId): bool = if `name _ ptr` != nil: target = `name _ ptr`[] elif `name _ ok`: let bdata = dag.getExistingForkedBlock(bid) if bdata.isErr: dag.handleUnexpectedLightClientError(bid.slot) `name _ ok` = false else: target = bdata.get.toBeaconBlockHeader() `name _ ptr` = addr target `name _ ok` template lazy_data(name: untyped): untyped {.dirty.} = ## `createLightClientUpdates` helper to lazily load cached light client state. var `name` {.noinit.}: CachedLightClientData `name`.finalized_slot = FAR_FUTURE_SLOT template `load _ name`(bid: BlockId) = if `name`.finalized_slot == FAR_FUTURE_SLOT: `name` = dag.getLightClientData(bid) template lazy_bid(name: untyped): untyped {.dirty.} = ## `createLightClientUpdates` helper to lazily load a known to exist block id. var `name` {.noinit.}: BlockId `name _ ok` = true `name`.slot = FAR_FUTURE_SLOT template `load _ name`(slot: Slot): bool = if `name _ ok` and `name`.slot == FAR_FUTURE_SLOT: let bsi = dag.getExistingBlockIdAtSlot(slot) if bsi.isErr: dag.handleUnexpectedLightClientError(slot) `name _ ok` = false else: `name` = bsi.get.bid `name _ ok` proc createLightClientUpdates( dag: ChainDAGRef, state: HashedBeaconStateWithSyncCommittee, blck: TrustedSignedBeaconBlockWithSyncAggregate, parent_bid: BlockId) = ## Create `LightClientUpdate` instances for a given block and its post-state, ## and keep track of best / latest ones. Data about the parent block's ## post-state must be cached (`cacheLightClientData`) before calling this. # Verify sync committee has sufficient participants template sync_aggregate(): auto = blck.asSigned().message.body.sync_aggregate template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits let num_active_participants = countOnes(sync_committee_bits).uint64 if num_active_participants < MIN_SYNC_COMMITTEE_PARTICIPANTS: return # Verify attested block (parent) is recent enough and that state is available template attested_bid(): auto = parent_bid let earliest_slot = dag.computeEarliestLightClientSlot attested_slot = attested_bid.slot if attested_slot < earliest_slot: return # Lazy variables to hold historic data lazy_header(attested_header) lazy_data(attested_data) lazy_bid(finalized_bid) lazy_header(finalized_header) # Update latest light client data template latest(): auto = dag.lcDataStore.cache.latest var newFinality = false newOptimistic = false let signature_slot = blck.message.slot is_later = if attested_slot != latest.attested_header.slot: attested_slot > latest.attested_header.slot else: signature_slot > latest.signature_slot if is_later and latest.attested_header.assign_attested_header(attested_bid): load_attested_data(attested_bid) let finalized_slot = attested_data.finalized_slot if finalized_slot == latest.finalized_header.slot: latest.finality_branch = attested_data.finality_branch elif finalized_slot == GENESIS_SLOT: latest.finalized_header.reset() latest.finality_branch = attested_data.finality_branch elif finalized_slot >= dag.tail.slot and load_finalized_bid(finalized_slot) and latest.finalized_header.assign_finalized_header(finalized_bid): latest.finality_branch = attested_data.finality_branch newFinality = true else: latest.finalized_header.reset() latest.finality_branch.reset() latest.sync_aggregate = sync_aggregate latest.signature_slot = signature_slot newOptimistic = true # Track best light client data for current period let attested_period = attested_slot.sync_committee_period signature_period = signature_slot.sync_committee_period if attested_period == signature_period: template next_sync_committee(): auto = state.data.next_sync_committee let isCommitteeFinalized = dag.isNextSyncCommitteeFinalized(attested_period) var best = if isCommitteeFinalized: dag.lcDataStore.cache.best.getOrDefault(attested_period) else: let key = (attested_period, state.syncCommitteeRoot) dag.lcDataStore.cache.pendingBest.getOrDefault(key) load_attested_data(attested_bid) let finalized_slot = attested_data.finalized_slot has_finality = finalized_slot >= dag.tail.slot and load_finalized_bid(finalized_slot) meta = LightClientUpdateMetadata( attested_slot: attested_slot, finalized_slot: finalized_slot, signature_slot: signature_slot, has_sync_committee: true, has_finality: has_finality, num_active_participants: num_active_participants) is_better = is_better_data(meta, best.toMeta) if is_better and best.attested_header.assign_attested_header(attested_bid): best.next_sync_committee = next_sync_committee best.next_sync_committee_branch = attested_data.next_sync_committee_branch if finalized_slot == best.finalized_header.slot: best.finality_branch = attested_data.finality_branch elif finalized_slot == GENESIS_SLOT: best.finalized_header.reset() best.finality_branch = attested_data.finality_branch elif has_finality and best.finalized_header.assign_finalized_header(finalized_bid): best.finality_branch = attested_data.finality_branch else: best.finalized_header.reset() best.finality_branch.reset() best.sync_aggregate = sync_aggregate best.signature_slot = signature_slot if isCommitteeFinalized: dag.lcDataStore.cache.best[attested_period] = best debug "Best LC update for period improved", period = attested_period, update = best else: let key = (attested_period, state.syncCommitteeRoot) dag.lcDataStore.cache.pendingBest[key] = best debug "Best LC update for period improved", period = key, update = best if newFinality and dag.lcDataStore.onLightClientFinalityUpdate != nil: dag.lcDataStore.onLightClientFinalityUpdate(latest) if newOptimistic and dag.lcDataStore.onLightClientOptimisticUpdate != nil: dag.lcDataStore.onLightClientOptimisticUpdate(latest.toOptimistic) proc processNewBlockForLightClient*( dag: ChainDAGRef, state: ForkedHashedBeaconState, signedBlock: ForkyTrustedSignedBeaconBlock, parentBid: BlockId) = ## Update light client data with information from a new block. if dag.lcDataStore.importMode == LightClientDataImportMode.None: return if signedBlock.message.slot < dag.computeEarliestLightClientSlot: return when signedBlock is bellatrix.TrustedSignedBeaconBlock: dag.cacheLightClientData(state.bellatrixData, signedBlock.toBlockId()) dag.createLightClientUpdates(state.bellatrixData, signedBlock, parentBid) elif signedBlock is altair.TrustedSignedBeaconBlock: dag.cacheLightClientData(state.altairData, signedBlock.toBlockId()) dag.createLightClientUpdates(state.altairData, signedBlock, parentBid) elif signedBlock is phase0.TrustedSignedBeaconBlock: raiseAssert "Unreachable" # `earliestSlot` cannot be before Altair else: {.error: "Unreachable".} proc processHeadChangeForLightClient*(dag: ChainDAGRef) = ## Update light client data to account for a new head block. ## Note that `dag.finalizedHead` is not yet updated when this is called. if dag.lcDataStore.importMode == LightClientDataImportMode.None: return let earliestSlot = dag.computeEarliestLightClientSlot if dag.head.slot < earliestSlot: return # Update `best` from `pendingBest` to ensure light client data # only refers to sync committees as selected by fork choice let headPeriod = dag.head.slot.sync_committee_period if not dag.isNextSyncCommitteeFinalized(headPeriod): let earliestPeriod = earliestSlot.sync_committee_period lowPeriod = max(dag.firstNonFinalizedPeriod, earliestPeriod) if headPeriod > lowPeriod: var tmpState = assignClone(dag.headState) for period in lowPeriod ..< headPeriod: let syncCommitteeRoot = dag.syncCommitteeRootForPeriod(tmpState[], period).valueOr: dag.handleUnexpectedLightClientError(period.start_slot) continue key = (period, syncCommitteeRoot) dag.lcDataStore.cache.best[period] = dag.lcDataStore.cache.pendingBest.getOrDefault(key) withState(dag.headState): # Common case separate to avoid `tmpState` copy when stateFork >= BeaconStateFork.Altair: let key = (headPeriod, state.syncCommitteeRoot) dag.lcDataStore.cache.best[headPeriod] = dag.lcDataStore.cache.pendingBest.getOrDefault(key) else: raiseAssert "Unreachable" proc processFinalizationForLightClient*( dag: ChainDAGRef, oldFinalizedHead: BlockSlot) = ## Prune cached data that is no longer useful for creating future ## `LightClientUpdate` and `LightClientBootstrap` instances. ## This needs to be called whenever `finalized_checkpoint` changes. if dag.lcDataStore.importMode == LightClientDataImportMode.None: return let earliestSlot = dag.computeEarliestLightClientSlot finalizedSlot = dag.finalizedHead.slot if finalizedSlot < earliestSlot: return # Cache `LightClientBootstrap` for newly finalized epoch boundary blocks let lowSlot = max(oldFinalizedHead.slot + 1, earliestSlot) var boundarySlot = finalizedSlot while boundarySlot >= lowSlot: let bsi = dag.getExistingBlockIdAtSlot(boundarySlot).valueOr: dag.handleUnexpectedLightClientError(boundarySlot) break bid = bsi.bid if bid.slot >= lowSlot: dag.lcDataStore.cache.bootstrap[bid.slot] = CachedLightClientBootstrap( current_sync_committee_branch: dag.getLightClientData(bid).current_sync_committee_branch) boundarySlot = bid.slot.nextEpochBoundarySlot if boundarySlot < SLOTS_PER_EPOCH: break boundarySlot -= SLOTS_PER_EPOCH # Prune light client data that is no longer referrable by future updates var bidsToDelete: seq[BlockId] for bid, data in dag.lcDataStore.cache.data: if bid.slot >= dag.finalizedHead.blck.slot: continue bidsToDelete.add bid for bid in bidsToDelete: dag.lcDataStore.cache.data.del bid # Prune bootstrap data that is no longer relevant var slotsToDelete: seq[Slot] for slot in dag.lcDataStore.cache.bootstrap.keys: if slot < earliestSlot: slotsToDelete.add slot for slot in slotsToDelete: dag.lcDataStore.cache.bootstrap.del slot # Prune best `LightClientUpdate` that are no longer relevant let earliestPeriod = earliestSlot.sync_committee_period var periodsToDelete: seq[SyncCommitteePeriod] for period in dag.lcDataStore.cache.best.keys: if period < earliestPeriod: periodsToDelete.add period for period in periodsToDelete: dag.lcDataStore.cache.best.del period # Prune best `LightClientUpdate` referring to non-finalized sync committees # that are no longer relevant, i.e., orphaned or too old let firstNonFinalizedPeriod = dag.firstNonFinalizedPeriod var keysToDelete: seq[(SyncCommitteePeriod, Eth2Digest)] for (period, committeeRoot) in dag.lcDataStore.cache.pendingBest.keys: if period < firstNonFinalizedPeriod: keysToDelete.add (period, committeeRoot) for key in keysToDelete: dag.lcDataStore.cache.pendingBest.del key func initLightClientDataStore*( serve: bool, importMode: LightClientDataImportMode, onLCFinalityUpdateCb: OnLightClientFinalityUpdateCallback = nil, onLCOptimisticUpdateCb: OnLightClientOptimisticUpdateCallback = nil ): LightClientDataStore = ## Initialize light client data collector. LightClientDataStore( serve: serve, importMode: importMode, onLightClientFinalityUpdate: onLCFinalityUpdateCb, onLightClientOptimisticUpdate: onLCOptimisticUpdateCb) proc initLightClientBootstrapForPeriod( dag: ChainDAGRef, period: SyncCommitteePeriod) = ## Compute and cache `LightClientBootstrap` data for all finalized ## epoch boundary blocks within a given sync committee period. if not dag.isNextSyncCommitteeFinalized(period): return let earliestSlot = dag.computeEarliestLightClientSlot periodStartSlot = period.start_slot periodEndSlot = periodStartSlot + SLOTS_PER_SYNC_COMMITTEE_PERIOD - 1 if periodEndSlot < earliestSlot: return let startTick = Moment.now() debug "Caching LC bootstrap data for period", period defer: let endTick = Moment.now() debug "LC bootstrap data for period cached", period, cacheDur = endTick - startTick let lowSlot = max(periodStartSlot, earliestSlot) highSlot = min(periodEndSlot, dag.finalizedHead.blck.slot) lowBoundarySlot = lowSlot.nextEpochBoundarySlot highBoundarySlot = highSlot.nextEpochBoundarySlot var tmpState = assignClone(dag.headState) tmpCache: StateCache nextBoundarySlot = lowBoundarySlot while nextBoundarySlot <= highBoundarySlot: defer: nextBoundarySlot += SLOTS_PER_EPOCH let bsi = dag.getExistingBlockIdAtSlot(nextBoundarySlot).valueOr: dag.handleUnexpectedLightClientError(nextBoundarySlot) continue bid = bsi.bid boundarySlot = bid.slot.nextEpochBoundarySlot if boundarySlot == nextBoundarySlot and bid.slot >= lowSlot and not dag.lcDataStore.cache.bootstrap.hasKey(bid.slot): if not dag.updateExistingState( tmpState[], bid.atSlot, save = false, tmpCache): dag.handleUnexpectedLightClientError(bid.slot) continue var cachedBootstrap {.noinit.}: CachedLightClientBootstrap cachedBootstrap.current_sync_committee_branch = withState(tmpState[]): when stateFork >= BeaconStateFork.Altair: state.data.build_proof(altair.CURRENT_SYNC_COMMITTEE_INDEX).get else: raiseAssert "Unreachable" dag.lcDataStore.cache.bootstrap[bid.slot] = cachedBootstrap proc initLightClientUpdateForPeriod( dag: ChainDAGRef, period: SyncCommitteePeriod) = ## Compute and cache the best `LightClientUpdate` within a given ## sync committee period up through the finalized head block. ## Non-finalized blocks are processed incrementally. if not dag.isNextSyncCommitteeFinalized(period): return let earliestSlot = dag.computeEarliestLightClientSlot periodStartSlot = period.start_slot periodEndSlot = periodStartSlot + SLOTS_PER_SYNC_COMMITTEE_PERIOD - 1 if periodEndSlot < earliestSlot: return if dag.lcDataStore.cache.best.hasKey(period): return let startTick = Moment.now() debug "Computing best LC update for period", period proc logBest(endTick = Moment.now()) = # Using a helper function reduces code size as the `defer` beneath is # replicated on every `return`, and the log statement allocates another # copy of the arguments on the stack for each instantiation (~1 MB stack!) debug "Best LC update for period computed", period, update = dag.lcDataStore.cache.best.getOrDefault(period), computeDur = endTick - startTick defer: logBest() proc maxParticipantsBlock( dag: ChainDAGRef, highBid: BlockId, lowSlot: Slot ): tuple[bid: Opt[BlockId], ok: bool] = ## Determine the earliest block with most sync committee signatures among ## ancestors of `highBid` with at least `lowSlot` as parent block slot. ## Return `err` if no block with `MIN_SYNC_COMMITTEE_PARTICIPANTS` exists. ## `bool` in result indicates whether no unexpected errors occurred. var maxParticipants = MIN_SYNC_COMMITTEE_PARTICIPANTS maxBid: Opt[BlockId] allOk = true bid = highBid while true: if bid.slot <= lowSlot: break let parentBid = dag.existingParent(bid).valueOr: dag.handleUnexpectedLightClientError(bid.slot) allOk = false break if parentBid.slot < lowSlot: break let bdata = dag.getExistingForkedBlock(bid).valueOr: dag.handleUnexpectedLightClientError(bid.slot) allOk = false break numParticipants = withBlck(bdata): when stateFork >= BeaconStateFork.Altair: countOnes(blck.message.body.sync_aggregate.sync_committee_bits) else: raiseAssert "Unreachable" if numParticipants >= maxParticipants: maxParticipants = numParticipants maxBid.ok bid bid = parentBid (bid: maxBid, ok: allOk) # Determine the block in the period with highest sync committee participation let lowSlot = max(periodStartSlot, earliestSlot) highSlot = min(periodEndSlot, dag.finalizedHead.blck.slot) highBsi = dag.getExistingBlockIdAtSlot(highSlot).valueOr: dag.handleUnexpectedLightClientError(highSlot) return highBid = highBsi.bid maxParticipantsRes = dag.maxParticipantsBlock(highBid, lowSlot) maxParticipantsBid = maxParticipantsRes.bid.valueOr: if maxParticipantsRes.ok: # No single valid block exists in the period dag.lcDataStore.cache.best[period] = default(altair.LightClientUpdate) return # The block with highest participation may refer to a `finalized_checkpoint` # in a different sync committee period. If that is the case, search for a # later block with a `finalized_checkpoint` within the given sync committee # period, despite it having a lower sync committee participation var tmpState = assignClone(dag.headState) signatureBid {.noinit.}, finalizedBid {.noinit.}: BlockId signatureBid.slot = FAR_FUTURE_SLOT finalizedBid.slot = FAR_FUTURE_SLOT while true: if signatureBid.slot == FAR_FUTURE_SLOT: signatureBid = maxParticipantsBid else: let nextLowSlot = signatureBid.slot + 1 signatureRes = dag.maxParticipantsBlock(highBid, nextLowSlot) signatureBid = signatureRes.bid.valueOr: signatureBid = maxParticipantsBid break let attestedBid = dag.existingParent(signatureBid).valueOr: dag.handleUnexpectedLightClientError(signatureBid.slot) continue finalizedEpoch = block: dag.withUpdatedExistingState(tmpState[], attestedBid.atSlot) do: withState(state): when stateFork >= BeaconStateFork.Altair: state.data.finalized_checkpoint.epoch else: raiseAssert "Unreachable" do: dag.handleUnexpectedLightClientError(attestedBid.slot) continue finalizedSlot = finalizedEpoch.start_slot finalizedBsi = if finalizedSlot >= dag.tail.slot: dag.getExistingBlockIdAtSlot(finalizedSlot).valueOr: dag.handleUnexpectedLightClientError(finalizedSlot) continue else: continue if finalizedBid.slot >= lowSlot: finalizedBid = finalizedBsi.bid break if signatureBid == maxParticipantsBid: finalizedBid = finalizedBsi.bid # For fallback `break` at start of loop # Save best light client data for given period var update {.noinit.}: altair.LightClientUpdate let attestedBid = dag.existingParent(signatureBid).valueOr: dag.handleUnexpectedLightClientError(signatureBid.slot) return dag.withUpdatedExistingState(tmpState[], attestedBid.atSlot) do: let bdata = dag.getExistingForkedBlock(bid).valueOr: dag.handleUnexpectedLightClientError(bid.slot) return withStateAndBlck(state, bdata): when stateFork >= BeaconStateFork.Altair: update.attested_header = blck.toBeaconBlockHeader() update.next_sync_committee = state.data.next_sync_committee update.next_sync_committee_branch = state.data.build_proof(altair.NEXT_SYNC_COMMITTEE_INDEX).get if finalizedBid.slot == FAR_FUTURE_SLOT: update.finality_branch.reset() else: update.finality_branch = state.data.build_proof(altair.FINALIZED_ROOT_INDEX).get else: raiseAssert "Unreachable" do: dag.handleUnexpectedLightClientError(attestedBid.slot) return if finalizedBid.slot == FAR_FUTURE_SLOT or finalizedBid.slot == GENESIS_SLOT: update.finalized_header.reset() else: let bdata = dag.getExistingForkedBlock(finalizedBid).valueOr: dag.handleUnexpectedLightClientError(finalizedBid.slot) return withBlck(bdata): update.finalized_header = blck.toBeaconBlockHeader() let bdata = dag.getExistingForkedBlock(signatureBid).valueOr: dag.handleUnexpectedLightClientError(signatureBid.slot) return withBlck(bdata): when stateFork >= BeaconStateFork.Altair: update.sync_aggregate = blck.asSigned().message.body.sync_aggregate else: raiseAssert "Unreachable" update.signature_slot = signatureBid.slot dag.lcDataStore.cache.best[period] = update proc initLightClientDataCache*(dag: ChainDAGRef) = ## Initialize cached light client data if dag.lcDataStore.importMode == LightClientDataImportMode.None: return dag.lcDataStore.cache.importTailSlot = dag.tail.slot if dag.lcDataStore.importMode == LightClientDataImportMode.OnlyNew: dag.lcDataStore.cache.importTailSlot = dag.head.slot var earliestSlot = dag.computeEarliestLightClientSlot if dag.head.slot < earliestSlot: return # Import light client data for finalized period through finalized head let finalizedSlot = dag.finalizedHead.slot finalizedPeriod = finalizedSlot.sync_committee_period dag.initLightClientBootstrapForPeriod(finalizedPeriod) dag.initLightClientUpdateForPeriod(finalizedPeriod) let lightClientStartTick = Moment.now() debug "Initializing cached light client data" template handleUnexpectedError(buggedBid: BlockId) = # Light client data is expected to be available from `earliestSlot` onward. # If there is an error, adjust `importTailSlot` to avoid failed lookups of # cached light client data. For new blocks / states, the caches can always # be updated incrementally, because those blocks / states are passed in # directly. It is only historical blocks (or sync committees) that depend # on a potentially corrupted database. doAssert buggedBid.slot > dag.lcDataStore.cache.importTailSlot dag.handleUnexpectedLightClientError(buggedBid.slot) earliestSlot = dag.computeEarliestLightClientSlot # Build list of block to process. # As it is slow to load states in descending order, # build a reverse todo list to then process them in ascending order let lowSlot = max(finalizedSlot, earliestSlot) var blocks = newSeqOfCap[BlockId](dag.head.slot - lowSlot + 1) bid = dag.head.bid while bid.slot > lowSlot: blocks.add bid bid = dag.existingParent(bid).valueOr: handleUnexpectedError(bid) break if bid.slot == lowSlot: blocks.add bid # Process blocks (reuses `dag.headState`, but restores it to the current head) var tmpState = assignClone(dag.headState) tmpCache, cache: StateCache oldCheckpoint: Checkpoint cpIndex = 0 for i in countdown(blocks.high, blocks.low): bid = blocks[i] if not dag.updateExistingState( dag.headState, bid.atSlot, save = false, cache): handleUnexpectedError(bid) continue let bdata = dag.getExistingForkedBlock(bid).valueOr: handleUnexpectedError(bid) continue withStateAndBlck(dag.headState, bdata): when stateFork >= BeaconStateFork.Altair: # Cache light client data (non-finalized blocks may refer to this) dag.cacheLightClientData(state, blck.toBlockId()) # Create `LightClientUpdate` instances if bid.slot != lowSlot: dag.createLightClientUpdates(state, blck, parentBid = blocks[i + 1]) else: raiseAssert "Unreachable" let lightClientEndTick = Moment.now() debug "Initialized cached light client data", initDur = lightClientEndTick - lightClientStartTick # Import historic data if dag.lcDataStore.importMode == LightClientDataImportMode.Full: let earliestPeriod = earliestSlot.sync_committee_period for period in earliestPeriod ..< finalizedPeriod: dag.initLightClientBootstrapForPeriod(period) dag.initLightClientUpdateForPeriod(period) proc getLightClientBootstrap*( dag: ChainDAGRef, blockRoot: Eth2Digest): Opt[altair.LightClientBootstrap] = if not dag.lcDataStore.serve: return err() let bdata = dag.getForkedBlock(blockRoot).valueOr: debug "LC bootstrap unavailable: Block not found", blockRoot return err() withBlck(bdata): let slot = blck.message.slot when stateFork >= BeaconStateFork.Altair: let earliestSlot = dag.computeEarliestLightClientSlot if slot < earliestSlot: debug "LC bootstrap unavailable: Block too old", slot return err() if slot > dag.finalizedHead.blck.slot: debug "LC bootstrap unavailable: Not finalized", blockRoot return err() var cachedBootstrap = dag.lcDataStore.cache.bootstrap.getOrDefault(slot) if cachedBootstrap.current_sync_committee_branch.isZeroMemory: if dag.lcDataStore.importMode == LightClientDataImportMode.OnDemand: let bsi = ? dag.getExistingBlockIdAtSlot(slot) var tmpState = assignClone(dag.headState) dag.withUpdatedExistingState(tmpState[], bsi) do: cachedBootstrap.current_sync_committee_branch = withState(state): when stateFork >= BeaconStateFork.Altair: state.data.build_proof(altair.CURRENT_SYNC_COMMITTEE_INDEX).get else: raiseAssert "Unreachable" do: return err() dag.lcDataStore.cache.bootstrap[slot] = cachedBootstrap else: debug "LC bootstrap unavailable: Data not cached", slot return err() let period = slot.sync_committee_period var tmpState = assignClone(dag.headState) var bootstrap {.noinit.}: altair.LightClientBootstrap bootstrap.header = blck.toBeaconBlockHeader() bootstrap.current_sync_committee = ? dag.existingCurrentSyncCommitteeForPeriod(tmpState[], period) bootstrap.current_sync_committee_branch = cachedBootstrap.current_sync_committee_branch return ok bootstrap else: debug "LC bootstrap unavailable: Block before Altair", slot return err() proc getLightClientUpdateForPeriod*( dag: ChainDAGRef, period: SyncCommitteePeriod): Option[altair.LightClientUpdate] = if not dag.lcDataStore.serve: return if dag.lcDataStore.importMode == LightClientDataImportMode.OnDemand: dag.initLightClientUpdateForPeriod(period) result = some(dag.lcDataStore.cache.best.getOrDefault(period)) let numParticipants = countOnes(result.get.sync_aggregate.sync_committee_bits) if numParticipants < MIN_SYNC_COMMITTEE_PARTICIPANTS: result.reset() proc getLightClientFinalityUpdate*( dag: ChainDAGRef): Option[altair.LightClientFinalityUpdate] = if not dag.lcDataStore.serve: return result = some(dag.lcDataStore.cache.latest) let numParticipants = countOnes(result.get.sync_aggregate.sync_committee_bits) if numParticipants < MIN_SYNC_COMMITTEE_PARTICIPANTS: result.reset() proc getLightClientOptimisticUpdate*( dag: ChainDAGRef): Option[altair.LightClientOptimisticUpdate] = if not dag.lcDataStore.serve: return result = some(dag.lcDataStore.cache.latest.toOptimistic) let numParticipants = countOnes(result.get.sync_aggregate.sync_committee_bits) if numParticipants < MIN_SYNC_COMMITTEE_PARTICIPANTS: result.reset()