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don't repeat already-included attestations (#2061) 

Don't repeat already-included attestations

Also removes the superfluous (and badly scaling) attestation-cache-eviction
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tersec 2020-12-15 15:16:10 +00:00 committed by GitHub
parent 4e191a06ac
commit 91786686d5
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 103 additions and 15 deletions
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99
beacon_chain/attestation_pool.nim
View File

@ -133,7 +133,7 @@ proc updateCurrent(pool: var AttestationPool, wallSlot: Slot) =
for k in keysToRemove:
pool.attestationAggregates.del k
proc addToAggregates(pool: var AttestationPool, attestation: Attestation) =
func addToAggregates(pool: var AttestationPool, attestation: Attestation) =
# do a lookup for the current slot and get it's associated htrs/attestations
var aggreated_attestation = pool.attestationAggregates.mgetOrPut(
attestation.data.slot, Table[Eth2Digest, Attestation]()).
@ -217,7 +217,8 @@ proc addAttestation*(pool: var AttestationPool,
if not found:
attestationsSeen.attestations.add(AttestationEntry(
data: attestation.data,
validations: @[validation]
validations: @[validation],
aggregation_bits: attestation.aggregation_bits
))
pool.addForkChoiceVotes(
attestation.data.slot, participants, attestation.data.beacon_block_root,
@ -243,7 +244,7 @@ proc addForkChoice*(pool: var AttestationPool,
error "Couldn't add block to fork choice, bug?",
blck = shortLog(blck), err = state.error
proc getAttestationsForSlot*(pool: AttestationPool, newBlockSlot: Slot):
proc getAttestationsForSlot(pool: AttestationPool, newBlockSlot: Slot):
Option[AttestationsSeen] =
if newBlockSlot < (GENESIS_SLOT + MIN_ATTESTATION_INCLUSION_DELAY):
debug "Too early for attestations", newBlockSlot = shortLog(newBlockSlot)
@ -283,7 +284,69 @@ iterator attestations*(pool: AttestationPool, slot: Option[Slot],
signature: validation.aggregate_signature
)
proc getAttestationsForBlock*(pool: AttestationPool,
func getAttestationDataKey(ad: AttestationData): AttestationDataKey =
# This determines the rest of the AttestationData
(ad.slot, ad.index, ad.source.epoch, ad.target.epoch)
func incorporateCacheAttestation(
pool: var AttestationPool, attestation: PendingAttestation) =
let key = attestation.data.getAttestationDataKey
try:
var validatorBits = pool.attestedValidators[key]
validatorBits.combine(attestation.aggregation_bits)
pool.attestedValidators[key] = validatorBits
except KeyError:
pool.attestedValidators[key] = attestation.aggregation_bits
func populateAttestationCache(pool: var AttestationPool, state: BeaconState) =
pool.attestedValidators.clear()
for pendingAttestation in state.previous_epoch_attestations:
pool.incorporateCacheAttestation(pendingAttestation)
for pendingAttestation in state.current_epoch_attestations:
pool.incorporateCacheAttestation(pendingAttestation)
func updateAttestationsCache(pool: var AttestationPool,
state: BeaconState) =
# There have likely been additional attestations integrated into BeaconState
# since last block production, an epoch change, or even a tree restructuring
# so that there's nothing in common in the BeaconState altogether, since the
# last time requested.
if (
(pool.lastPreviousEpochAttestationsLen == 0 or
(pool.lastPreviousEpochAttestationsLen <= state.previous_epoch_attestations.len and
pool.lastPreviousEpochAttestation ==
state.previous_epoch_attestations[pool.lastPreviousEpochAttestationsLen - 1])) and
(pool.lastCurrentEpochAttestationsLen == 0 or
(pool.lastCurrentEpochAttestationsLen <= state.current_epoch_attestations.len and
pool.lastCurrentEpochAttestation ==
state.current_epoch_attestations[pool.lastCurrentEpochAttestationsLen - 1]))
):
# There are multiple validators attached to this node proposing in the
# same epoch. As such, incorporate that new attestation. Both previous
# and current attestations lists might have been appended to.
for i in pool.lastPreviousEpochAttestationsLen ..<
state.previous_epoch_attestations.len:
pool.incorporateCacheAttestation(state.previous_epoch_attestations[i])
for i in pool.lastCurrentEpochAttestationsLen ..<
state.current_epoch_attestations.len:
pool.incorporateCacheAttestation(state.current_epoch_attestations[i])
else:
# Tree restructuring or other cache flushing event. This must trigger
# sometimes to clear old attestations.
pool.populateAttestationCache(state)
pool.lastPreviousEpochAttestationsLen = state.previous_epoch_attestations.len
pool.lastCurrentEpochAttestationsLen = state.current_epoch_attestations.len
if pool.lastPreviousEpochAttestationsLen > 0:
pool.lastPreviousEpochAttestation =
state.previous_epoch_attestations[pool.lastPreviousEpochAttestationsLen - 1]
if pool.lastCurrentEpochAttestationsLen > 0:
pool.lastCurrentEpochAttestation =
state.current_epoch_attestations[pool.lastCurrentEpochAttestationsLen - 1]
proc getAttestationsForBlock*(pool: var AttestationPool,
state: BeaconState,
cache: var StateCache): seq[Attestation] =
## Retrieve attestations that may be added to a new block at the slot of the
@ -291,15 +354,10 @@ proc getAttestationsForBlock*(pool: AttestationPool,
let newBlockSlot = state.slot
var attestations: seq[AttestationEntry]
# This potentially creates problems with lots of repeated attestations,
# as a bunch of synchronized beacon_nodes do almost the opposite of the
# intended thing -- sure, _blocks_ have to be popular (via attestation)
# but _attestations_ shouldn't have to be so frequently repeated, as an
# artifact of this state-free, identical-across-clones choice basis. In
# addAttestation, too, the new attestations get added to the end, while in
# these functions, it's reading from the beginning, et cetera. This all
# needs a single unified strategy.
for i in max(1, newBlockSlot.int64 - ATTESTATION_LOOKBACK.int64) .. newBlockSlot.int64:
pool.updateAttestationsCache(state)
for i in max(1, newBlockSlot.int64 - ATTESTATION_LOOKBACK.int64) ..
newBlockSlot.int64:
let maybeSlotData = getAttestationsForSlot(pool, i.Slot)
if maybeSlotData.isSome:
insert(attestations, maybeSlotData.get.attestations)
@ -336,6 +394,17 @@ proc getAttestationsForBlock*(pool: AttestationPool,
attestation.aggregation_bits.combine(a.validations[i].aggregation_bits)
agg.aggregate(a.validations[i].aggregate_signature)
# Since each validator attests exactly once per epoch and its attestation
# has been validated to have been included in the attestation pool, there
# only exists one possible slot/committee combination to check.
try:
if a.aggregation_bits.isSubsetOf(
pool.attestedValidators[a.data.getAttestationDataKey]):
continue
except KeyError:
# No record of inclusion, so go ahead and include attestation.
discard
attestation.signature = agg.finish()
result.add(attestation)
@ -344,7 +413,7 @@ proc getAttestationsForBlock*(pool: AttestationPool,
attestationSlot = newBlockSlot - 1
return
proc getAggregatedAttestation*(pool: AttestationPool,
func getAggregatedAttestation*(pool: AttestationPool,
slot: Slot,
ad_htr: Eth2Digest): Option[Attestation] =
try:
@ -353,7 +422,7 @@ proc getAggregatedAttestation*(pool: AttestationPool,
return some pool.attestationAggregates[slot][ad_htr]
except KeyError:
doAssert(false) # shouldn't be possible because we check with `contains`
return none(Attestation)
none(Attestation)
proc getAggregatedAttestation*(pool: AttestationPool,
slot: Slot,

19
beacon_chain/beacon_node_types.nim
View File

@ -36,6 +36,7 @@ type
## Each entry holds the known signatures for a particular, distinct vote
data*: AttestationData
blck*: BlockRef
aggregation_bits*: CommitteeValidatorsBits
validations*: seq[Validation]
AttestationsSeen* = object
@ -47,6 +48,9 @@ type
## TODO this could be a Table[AttestationData, seq[Validation] or something
## less naive
# These provide types for attestation pool's cache attestations.
AttestationDataKey* = (Slot, uint64, Epoch, Epoch)
AttestationPool* = object
## The attestation pool keeps track of all attestations that potentially
## could be added to a block during block production.
@ -74,6 +78,21 @@ type
nextAttestationEpoch*: seq[tuple[subnet: Epoch, aggregate: Epoch]] ## \
## sequence based on validator indices
attestedValidators*:
Table[AttestationDataKey, CommitteeValidatorsBits] ## \
## Cache for quick lookup during beacon block construction of attestations
## which have already been included, and therefore should be skipped. This
## isn't that useful for a couple validators per node, but pays off when a
## larger number of local validators is attached.
lastPreviousEpochAttestationsLen*: int
lastCurrentEpochAttestationsLen*: int ## \
lastPreviousEpochAttestation*: PendingAttestation
lastCurrentEpochAttestation*: PendingAttestation
## Used to detect and incorporate new attestations since the last block
## created. Defaults are fine as initial values and don't need explicit
## initialization.
ExitPool* = object
## The exit pool tracks attester slashings, proposer slashings, and
## voluntary exits that could be added to a proposed block.