277 lines
10 KiB
Nim
277 lines
10 KiB
Nim
# beacon_chain
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# Copyright (c) 2021-2022 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import
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std/[tables, sequtils],
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bearssl,
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stew/shims/[sets, hashes], chronicles,
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eth/p2p/discoveryv5/random2,
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../spec/datatypes/base,
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../spec/[helpers, network],
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../consensus_object_pools/[block_pools_types, spec_cache]
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export base, helpers, network, sets, tables
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{.push raises: [Defect].}
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const
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SUBNET_SUBSCRIPTION_LEAD_TIME_SLOTS* = 4 ##\
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## The number of slots before we're up for aggregation duty that we'll
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## actually subscribe to the subnet we're aggregating for - this gives
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## the node time to find a mesh etc - can likely be further trimmed
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KNOWN_VALIDATOR_DECAY = 3 * 32 * SLOTS_PER_EPOCH ##\
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## The number of slots before we "forget" about validators that have
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## registered for duties - once we've forgotten about a validator, we'll
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## eventually decrease the number of stability subnets we're subscribed to -
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## 3 epochs because we perform attestations once every epoch, +1 to deal
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## with rounding + 1 to deal with the network growing beyond 260k validators
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## and us not validating every epoch any more.
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## When known validators decrease, we will keep the stability subnet around
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## until it "naturally" expires.
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type
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AggregatorDuty* = object
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subnet_id*: SubnetId
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slot*: Slot
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ActionTracker* = object
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rng: ref BrHmacDrbgContext
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subscribeAllAttnets*: bool
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currentSlot*: Slot ##\
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## Duties that we accept are limited to a range around the current slot
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subscribedSubnets*: AttnetBits ##\
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## All subnets we're currently subscribed to
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stabilitySubnets: seq[tuple[subnet_id: SubnetId, expiration: Epoch]] ##\
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## The subnets on which we listen and broadcast gossip traffic to maintain
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## the health of the network - these are advertised in the ENR
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nextCycleEpoch*: Epoch
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# Used to track the next attestation and proposal slots using an
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# epoch-relative coordinate system. Doesn't need initialization.
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attestingSlots*: array[2, uint32]
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proposingSlots*: array[2, uint32]
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lastCalculatedEpoch*: Epoch
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dependentRoot*: Eth2Digest
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## The latest dependent root we used to compute attestation duties
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## for internal validators
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knownValidators*: Table[ValidatorIndex, Slot] ##\
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## Validators that we've recently seen - we'll subscribe to one stability
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## subnet for each such validator - the slot is used to expire validators
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## that no longer are posting duties
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duties*: HashSet[AggregatorDuty] ##\
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## Known aggregation duties in the near future - before each such
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## duty, we'll subscribe to the corresponding subnet to collect
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## attestations for the aggregate
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func hash*(x: AggregatorDuty): Hash =
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hashAllFields(x)
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# https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/validator.md#phase-0-attestation-subnet-stability
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func randomStabilitySubnet*(
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self: ActionTracker, epoch: Epoch): tuple[subnet_id: SubnetId, expiration: Epoch] =
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(
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self.rng[].rand(ATTESTATION_SUBNET_COUNT - 1).SubnetId,
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epoch + EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION +
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self.rng[].rand(EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION.int).uint64,
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)
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proc registerDuty*(
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tracker: var ActionTracker, slot: Slot, subnet_id: SubnetId,
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vidx: ValidatorIndex, isAggregator: bool) =
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# Only register relevant duties
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if slot < tracker.currentSlot or
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slot + (SLOTS_PER_EPOCH * 2) <= tracker.currentSlot:
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debug "Irrelevant duty", slot, subnet_id, vidx
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return
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tracker.knownValidators[vidx] = slot # Update validator last-seen registry
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if isAggregator:
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let newDuty = AggregatorDuty(slot: slot, subnet_id: subnet_id)
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if newDuty in tracker.duties:
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return
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debug "Registering aggregation duty", slot, subnet_id, vidx
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tracker.duties.incl(newDuty)
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const allSubnetBits = block:
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var res: AttnetBits
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for i in 0..<res.len: res[i] = true
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res
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func aggregateSubnets*(tracker: ActionTracker, wallSlot: Slot): AttnetBits =
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var res: AttnetBits
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# Subscribe to subnets for upcoming duties
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for duty in tracker.duties:
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if wallSlot <= duty.slot and
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wallSlot + SUBNET_SUBSCRIPTION_LEAD_TIME_SLOTS > duty.slot:
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res[duty.subnet_id.int] = true
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res
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func stabilitySubnets*(tracker: ActionTracker, slot: Slot): AttnetBits =
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if tracker.subscribeAllAttnets:
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allSubnetBits
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else:
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var res: AttnetBits
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for v in tracker.stabilitySubnets:
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res[v.subnet_id.int] = true
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res
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func updateSlot*(tracker: var ActionTracker, wallSlot: Slot) =
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# Prune duties from the past - this collection is kept small because there
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# are only so many slot/subnet combos - prune both internal and API-supplied
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# duties at the same time
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tracker.duties.keepItIf(it.slot >= wallSlot)
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# Keep stability subnets for as long as validators are validating
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var toPrune: seq[ValidatorIndex]
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for k, v in tracker.knownValidators:
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if v + KNOWN_VALIDATOR_DECAY < wallSlot: toPrune.add k
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for k in toPrune: tracker.knownValidators.del k
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# One stability subnet per known validator
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static: doAssert RANDOM_SUBNETS_PER_VALIDATOR == 1
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# https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/validator.md#phase-0-attestation-subnet-stability
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let expectedSubnets =
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min(ATTESTATION_SUBNET_COUNT, tracker.knownValidators.len)
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let epoch = wallSlot.epoch
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block:
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# If we have too many stability subnets, remove some expired ones
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var i = 0
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while tracker.stabilitySubnets.len > expectedSubnets and
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i < tracker.stabilitySubnets.len:
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if epoch >= tracker.stabilitySubnets[i].expiration:
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tracker.stabilitySubnets.delete(i)
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else:
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inc i
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for ss in tracker.stabilitySubnets.mitems():
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if epoch >= ss.expiration:
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ss = tracker.randomStabilitySubnet(epoch)
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# and if we have too few, add a few more
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for i in tracker.stabilitySubnets.len..<expectedSubnets:
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tracker.stabilitySubnets.add(tracker.randomStabilitySubnet(epoch))
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tracker.currentSlot = wallSlot
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func getNextValidatorAction*(
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actionSlotSource: auto, lastCalculatedEpoch: Epoch, slot: Slot): Slot =
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# The relevant actions are in, depending on calculated bounds:
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# [aS[epoch mod 2], aS[1 - (epoch mod 2)]]
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# current epoch next epoch
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let orderedActionSlots = [
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actionSlotSource[ slot.epoch mod 2'u64],
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actionSlotSource[1 - (slot.epoch mod 2'u64)]]
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static: doAssert MIN_ATTESTATION_INCLUSION_DELAY == 1
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# Cleverer ways exist, but a short loop is fine. O(n) vs O(log n) isn't that
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# important when n is 32 or 64, with early exit on average no more than half
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# through.
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for i in [0'u64, 1'u64]:
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let bitmapEpoch = slot.epoch + i
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if bitmapEpoch > lastCalculatedEpoch:
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return FAR_FUTURE_SLOT
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for slotOffset in 0 ..< SLOTS_PER_EPOCH:
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let nextActionSlot = start_slot(bitmapEpoch) + slotOffset
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if ((orderedActionSlots[i] and (1'u32 shl slotOffset)) != 0) and
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nextActionSlot > slot:
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return nextActionSlot
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FAR_FUTURE_SLOT
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func getNextAttestationSlot*(tracker: ActionTracker, slot: Slot): Slot =
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getNextValidatorAction(
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tracker.attestingSlots,
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tracker.lastCalculatedEpoch, slot)
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func getNextProposalSlot*(tracker: ActionTracker, slot: Slot): Slot =
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getNextValidatorAction(
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tracker.proposingSlots,
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tracker.lastCalculatedEpoch, slot)
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func dependentRoot(epoch: Epoch, head, tail: BlockRef): Eth2Digest =
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head.prevDependentBlock(tail, epoch).root
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func needsUpdate*(
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tracker: ActionTracker, epoch: Epoch, head, tail: BlockRef): bool =
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# Using prevDependentBlock here means we lock the action tracking to
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# the dependent root for attestation duties and not block proposal -
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# however, the risk of a proposer reordering in the last epoch is small
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# and the action tracker is speculative in nature.
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tracker.dependentRoot != dependentRoot(epoch, head, tail)
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func updateActions*(
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tracker: var ActionTracker, epochRef: EpochRef, head, tail: BlockRef) =
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# Updates the schedule for upcoming attestation and proposal work
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let
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epoch = epochRef.epoch
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if not tracker.needsUpdate(epoch, head, tail):
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return
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tracker.dependentRoot = dependentRoot(epoch, head, tail)
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tracker.lastCalculatedEpoch = epoch
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let validatorIndices = toHashSet(toSeq(tracker.knownValidators.keys()))
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# Update proposals
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tracker.proposingSlots[epoch mod 2] = 0
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for i, proposer in epochRef.beacon_proposers:
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if proposer.isSome and proposer.get() in validatorIndices:
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tracker.proposingSlots[epoch mod 2] =
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tracker.proposingSlots[epoch mod 2] or (1'u32 shl i)
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tracker.attestingSlots[epoch mod 2] = 0
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# The relevant bitmaps are 32 bits each.
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static: doAssert SLOTS_PER_EPOCH <= 32
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for (committeeIndex, subnet_id, slot) in
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get_committee_assignments(epochRef, validatorIndices):
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doAssert epoch(slot) == epoch
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# Each get_committee_assignments() call here is on the next epoch. At any
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# given time, only care about two epochs, the current and next epoch. So,
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# after it is done for an epoch, [aS[epoch mod 2], aS[1 - (epoch mod 2)]]
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# provides, sequentially, the current and next epochs' slot schedules. If
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# get_committee_assignments() has not been called for the next epoch yet,
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# typically because there hasn't been a block in the current epoch, there
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# isn't valid information in aS[1 - (epoch mod 2)], and only slots within
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# the current epoch can be known. Usually, this is not a major issue, but
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# when there hasn't been a block substantially through an epoch, it might
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# prove misleading to claim that there aren't attestations known, when it
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# only might be known either way for 3 more slots. However, it's also not
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# as important to attest when blocks aren't flowing as only attestions in
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# blocks garner rewards.
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tracker.attestingSlots[epoch mod 2] =
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tracker.attestingSlots[epoch mod 2] or
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(1'u32 shl (slot mod SLOTS_PER_EPOCH))
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func init*(
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T: type ActionTracker, rng: ref BrHmacDrbgContext,
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subscribeAllAttnets: bool): T =
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T(
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rng: rng,
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subscribeAllAttnets: subscribeAllAttnets
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)
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