nimbus-eth2/beacon_chain/validators/action_tracker.nim

248 lines
9.1 KiB
Nim

import
std/[tables, sequtils],
bearssl,
stew/shims/[sets, hashes], chronicles,
eth/p2p/discoveryv5/random2,
../spec/datatypes/base,
../spec/[helpers, network],
../consensus_object_pools/[block_pools_types, spec_cache]
export base, helpers, network, sets, tables
const
SUBNET_SUBSCRIPTION_LEAD_TIME_SLOTS* = 4 ##\
## The number of slots before we're up for aggregation duty that we'll
## actually subscribe to the subnet we're aggregating for - this gives
## the node time to find a mesh etc - can likely be further trimmed
KNOWN_VALIDATOR_DECAY = 3 * 32 * SLOTS_PER_EPOCH ##\
## The number of slots before we "forget" about validators that have
## registered for duties - once we've forgotten about a validator, we'll
## eventually decrease the number of stability subnets we're subscribed to -
## 3 epochs because we perform attestations once every epoch, +1 to deal
## with rounding + 1 to deal with the network growing beyond 260k validators
## and us not validating every epoch any more.
## When known validators decrease, we will keep the stability subnet around
## until it "naturally" expires.
type
AggregatorDuty* = object
subnet_id*: SubnetId
slot*: Slot
ActionTracker* = object
rng: ref BrHmacDrbgContext
subscribeAllSubnets*: bool
currentSlot*: Slot ##\
## Duties that we accept are limited to a range around the current slot
subscribedSubnets*: AttnetBits ##\
## All subnets we're currently subscribed to
stabilitySubnets: seq[tuple[subnet_id: SubnetId, expiration: Epoch]] ##\
## The subnets on which we listen and broadcast gossip traffic to maintain
## the health of the network - these are advertised in the ENR
nextCycleEpoch*: Epoch
# Used to track the next attestation and proposal slots using an
# epoch-relative coordinate system. Doesn't need initialization.
attestingSlots*: array[2, uint32]
proposingSlots*: array[2, uint32]
lastCalculatedEpoch*: Epoch
knownValidators*: Table[ValidatorIndex, Slot] ##\
## Validators that we've recently seen - we'll subscribe to one stability
## subnet for each such validator - the slot is used to expire validators
## that no longer are posting duties
duties*: HashSet[AggregatorDuty] ##\
## Known aggregation duties in the near future - before each such
## duty, we'll subscribe to the corresponding subnet to collect
## attestations for the aggregate
func hash*(x: AggregatorDuty): Hash =
hashAllFields(x)
# https://github.com/ethereum/consensus-specs/blob/v1.1.8/specs/phase0/validator.md#phase-0-attestation-subnet-stability
func randomStabilitySubnet*(
self: ActionTracker, epoch: Epoch): tuple[subnet_id: SubnetId, expiration: Epoch] =
(
self.rng[].rand(ATTESTATION_SUBNET_COUNT - 1).SubnetId,
epoch + EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION +
self.rng[].rand(EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION.int).uint64,
)
proc registerDuty*(
tracker: var ActionTracker, slot: Slot, subnet_id: SubnetId,
vidx: ValidatorIndex, isAggregator: bool) =
# Only register relevant duties
if slot < tracker.currentSlot or
slot + (SLOTS_PER_EPOCH * 2) <= tracker.currentSlot:
debug "Irrelevant duty", slot, subnet_id, vidx
return
tracker.knownValidators[vidx] = slot # Update validator last-seen registry
if isAggregator:
let newDuty = AggregatorDuty(slot: slot, subnet_id: subnet_id)
if newDuty in tracker.duties:
return
debug "Registering aggregation duty", slot, subnet_id, vidx
tracker.duties.incl(newDuty)
const allSubnetBits = block:
var res: AttnetBits
for i in 0..<res.len: res[i] = true
res
func aggregateSubnets*(tracker: ActionTracker, wallSlot: Slot): AttnetBits =
var res: AttnetBits
# Subscribe to subnets for upcoming duties
for duty in tracker.duties:
if wallSlot <= duty.slot and
wallSlot + SUBNET_SUBSCRIPTION_LEAD_TIME_SLOTS > duty.slot:
res[duty.subnet_id.int] = true
res
func stabilitySubnets*(tracker: ActionTracker, slot: Slot): AttnetBits =
if tracker.subscribeAllSubnets:
allSubnetBits
else:
var res: AttnetBits
for v in tracker.stabilitySubnets:
res[v.subnet_id.int] = true
res
func updateSlot*(tracker: var ActionTracker, wallSlot: Slot) =
# Prune duties from the past - this collection is kept small because there
# are only so many slot/subnet combos - prune both internal and API-supplied
# duties at the same time
tracker.duties.keepItIf(it.slot >= wallSlot)
# Keep stability subnets for as long as validators are validating
var toPrune: seq[ValidatorIndex]
for k, v in tracker.knownValidators:
if v + KNOWN_VALIDATOR_DECAY < wallSlot: toPrune.add k
for k in toPrune: tracker.knownValidators.del k
# One stability subnet per known validator
static: doAssert RANDOM_SUBNETS_PER_VALIDATOR == 1
# https://github.com/ethereum/consensus-specs/blob/v1.1.8/specs/phase0/validator.md#phase-0-attestation-subnet-stability
let expectedSubnets =
min(ATTESTATION_SUBNET_COUNT, tracker.knownValidators.len)
let epoch = wallSlot.epoch
block:
# If we have too many stability subnets, remove some expired ones
var i = 0
while tracker.stabilitySubnets.len > expectedSubnets and
i < tracker.stabilitySubnets.len:
if epoch >= tracker.stabilitySubnets[i].expiration:
tracker.stabilitySubnets.delete(i)
else:
inc i
for ss in tracker.stabilitySubnets.mitems():
if epoch >= ss.expiration:
ss = tracker.randomStabilitySubnet(epoch)
# and if we have too few, add a few more
for i in tracker.stabilitySubnets.len..<expectedSubnets:
tracker.stabilitySubnets.add(tracker.randomStabilitySubnet(epoch))
tracker.currentSlot = wallSlot
func getNextValidatorAction*(
actionSlotSource: auto, lastCalculatedEpoch: Epoch, slot: Slot): Slot =
# The relevant actions are in, depending on calculated bounds:
# [aS[epoch mod 2], aS[1 - (epoch mod 2)]]
# current epoch next epoch
let orderedActionSlots = [
actionSlotSource[ slot.epoch mod 2'u64],
actionSlotSource[1 - (slot.epoch mod 2'u64)]]
static: doAssert MIN_ATTESTATION_INCLUSION_DELAY == 1
# Cleverer ways exist, but a short loop is fine. O(n) vs O(log n) isn't that
# important when n is 32 or 64, with early exit on average no more than half
# through.
for i in [0'u64, 1'u64]:
let bitmapEpoch = slot.epoch + i
if bitmapEpoch > lastCalculatedEpoch:
return FAR_FUTURE_SLOT
for slotOffset in 0 ..< SLOTS_PER_EPOCH:
let nextActionSlot = start_slot(bitmapEpoch) + slotOffset
if ((orderedActionSlots[i] and (1'u32 shl slotOffset)) != 0) and
nextActionSlot > slot:
return nextActionSlot
FAR_FUTURE_SLOT
func getNextAttestationSlot*(tracker: ActionTracker, slot: Slot): Slot =
getNextValidatorAction(
tracker.attestingSlots,
tracker.lastCalculatedEpoch, slot)
func getNextProposalSlot*(tracker: ActionTracker, slot: Slot): Slot =
getNextValidatorAction(
tracker.proposingSlots,
tracker.lastCalculatedEpoch, slot)
proc updateActions*(tracker: var ActionTracker, epochRef: EpochRef) =
# Updates the schedule for upcoming attestation and proposal work
let
epoch = epochRef.epoch
if tracker.lastCalculatedEpoch == epoch:
return
tracker.lastCalculatedEpoch = epoch
let validatorIndices = toHashSet(toSeq(tracker.knownValidators.keys()))
# Update proposals
tracker.proposingSlots[epoch mod 2] = 0
for i, proposer in epochRef.beacon_proposers:
if proposer.isSome and proposer.get() in validatorIndices:
tracker.proposingSlots[epoch mod 2] =
tracker.proposingSlots[epoch mod 2] or (1'u32 shl i)
tracker.attestingSlots[epoch mod 2] = 0
# The relevant bitmaps are 32 bits each.
static: doAssert SLOTS_PER_EPOCH <= 32
for (committeeIndex, subnet_id, slot) in
get_committee_assignments(epochRef, validatorIndices):
doAssert epoch(slot) == epoch
# Each get_committee_assignments() call here is on the next epoch. At any
# given time, only care about two epochs, the current and next epoch. So,
# after it is done for an epoch, [aS[epoch mod 2], aS[1 - (epoch mod 2)]]
# provides, sequentially, the current and next epochs' slot schedules. If
# get_committee_assignments() has not been called for the next epoch yet,
# typically because there hasn't been a block in the current epoch, there
# isn't valid information in aS[1 - (epoch mod 2)], and only slots within
# the current epoch can be known. Usually, this is not a major issue, but
# when there hasn't been a block substantially through an epoch, it might
# prove misleading to claim that there aren't attestations known, when it
# only might be known either way for 3 more slots. However, it's also not
# as important to attest when blocks aren't flowing as only attestions in
# blocks garner rewards.
tracker.attestingSlots[epoch mod 2] =
tracker.attestingSlots[epoch mod 2] or
(1'u32 shl (slot mod SLOTS_PER_EPOCH))
proc init*(T: type ActionTracker, rng: ref BrHmacDrbgContext, subscribeAllSubnets: bool): T =
T(
rng: rng,
subscribeAllSubnets: subscribeAllSubnets
)