Add support for dealing with overlapping attestations (#262)
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@ -13,20 +13,21 @@ proc init*(T: type AttestationPool, blockPool: BlockPool): T =
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latestAttestations: initTable[ValidatorPubKey, BlockRef]()
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)
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proc combine*(tgt: var Attestation, src: Attestation, flags: UpdateFlags) =
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# Combine the signature and participation bitfield, with the assumption that
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# the same data is being signed!
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## Combine the signature and participation bitfield, with the assumption that
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## the same data is being signed - if the signatures overlap, they are not
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## combined.
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doAssert tgt.data == src.data
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# TODO:
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# when BLS signatures are combined, we must ensure that
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# the same participant key is not included on both sides
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tgt.aggregation_bitfield.combine(src.aggregation_bitfield)
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# In a BLS aggregate signature, one needs to count how many times a
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# particular public key has been added - since we use a single bit per key, we
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# can only it once, thus we can never combine signatures that overlap already!
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if not tgt.aggregation_bitfield.overlaps(src.aggregation_bitfield):
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tgt.aggregation_bitfield.combine(src.aggregation_bitfield)
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if skipValidation notin flags:
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tgt.aggregate_signature.combine(src.aggregate_signature)
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if skipValidation notin flags:
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tgt.aggregate_signature.combine(src.aggregate_signature)
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proc validate(
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state: BeaconState, attestation: Attestation, flags: UpdateFlags): bool =
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@ -113,6 +114,7 @@ proc slotIndex(
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# epoch to now, because these are the attestations that may affect the voting
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# outcome. Some of these attestations will already have been added to blocks,
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# while others are fresh off the network.
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# TODO only the latest vote of each validator counts. Can we use that somehow?
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doAssert attestationSlot >= pool.startingSlot,
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"""
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@ -186,15 +188,14 @@ proc add*(pool: var AttestationPool,
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for a in slotData.attestations.mitems():
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if a.data == attestation.data:
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for v in a.validations:
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if v.aggregation_bitfield.overlaps(validation.aggregation_bitfield):
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# TODO this check is here so that later, when we combine signatures,
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# there is no overlap (each validator must be represented once
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# only). this is wrong - we could technically receive
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# attestations that have already been combined (for example when
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# feeding in attestations from blocks, which we're not doing yet)
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# but then we'll also have to update the combine logic to deal
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# with this complication.
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debug "Ignoring overlapping attestation",
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if validation.aggregation_bitfield.isSubsetOf(v.aggregation_bitfield):
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# The validations in the new attestation are a subset of one of the
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# attestations that we already have on file - no need to add this
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# attestation to the database
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# TODO what if the new attestation is useful for creating bigger
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# sets by virtue of not overlapping with some other attestation
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# and therefore being useful after all?
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debug "Ignoring subset attestation",
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existingParticipants = get_attestation_participants(
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state, a.data, v.aggregation_bitfield),
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newParticipants = participants
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@ -202,12 +203,25 @@ proc add*(pool: var AttestationPool,
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break
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if not found:
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# Attestations in the pool that are a subset of the new attestation
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# can now be removed per same logic as above
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a.validations.keepItIf(
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if it.aggregation_bitfield.isSubsetOf(
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validation.aggregation_bitfield):
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debug "Removing subset attestation",
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existingParticipants = get_attestation_participants(
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state, a.data, it.aggregation_bitfield),
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newParticipants = participants
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false
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else:
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true)
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a.validations.add(validation)
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pool.updateLatestVotes(state, attestationSlot, participants, a.blck)
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info "Attestation resolved",
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attestationData = shortLog(attestation.data),
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validations = a.validations.len() # TODO popcount of union
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validations = a.validations.len()
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found = true
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@ -286,6 +300,13 @@ proc getAttestationsForBlock*(
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continue
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for v in a.validations[1..^1]:
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# TODO We need to select a set of attestations that maximise profit by
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# adding the largest combined attestation set that we can find - this
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# unfortunately looks an awful lot like
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# https://en.wikipedia.org/wiki/Set_packing - here we just iterate
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# and naively add as much as possible in one go, by we could also
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# add the same attestation data twice, as long as there's at least
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# one new attestation in there
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if not attestation.aggregation_bitfield.overlaps(
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v.aggregation_bitfield):
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attestation.aggregation_bitfield.combine(
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@ -429,10 +429,9 @@ proc onBeaconBlock(node: BeaconNode, blck: BeaconBlock) =
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# The block we received contains attestations, and we might not yet know about
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# all of them. Let's add them to the attestation pool - in case they block
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# is not yet resolved, neither will the attestations be!
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# TODO shouldn't add attestations if the block turns out to be invalid..
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for attestation in blck.body.attestations:
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# TODO attestation pool needs to be taught to deal with overlapping
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# attestations!
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discard # node.onAttestation(attestation)
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node.onAttestation(attestation)
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proc handleAttestations(node: BeaconNode, head: BlockRef, slot: Slot) =
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## Perform all attestations that the validators attached to this node should
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@ -1,4 +1,4 @@
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import byteutils, json_serialization
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import byteutils, json_serialization, std_shims/support/bitops2
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type
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BitField* = object
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@ -45,7 +45,19 @@ func combine*(tgt: var BitField, src: BitField) =
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for i in 0 ..< tgt.bits.len:
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tgt.bits[i] = tgt.bits[i] or src.bits[i]
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proc overlaps*(a, b: BitField): bool =
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func overlaps*(a, b: BitField): bool =
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for i in 0..<a.bits.len:
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if (a.bits[i] and b.bits[i]) > 0'u8:
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return true
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func countOnes*(a: BitField): int {.inline.} =
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for v in a.bits: result += countOnes(v)
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func len*(a: BitField): int {.inline.} =
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countOnes(a)
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func isSubsetOf*(a, b: Bitfield): bool =
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for i in 0 ..< (len(a.bits) * 8):
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if get_bitfield_bit(a, i) and not get_bitfield_bit(b, i):
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return false
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true
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@ -11,71 +11,145 @@ import
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../beacon_chain/spec/[beaconstate, crypto, datatypes, digest, helpers, validator],
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../beacon_chain/[beacon_node_types, attestation_pool, block_pool, extras, state_transition, ssz]
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template withPool(body: untyped) =
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mixin genState, genBlock
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var
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blockPool {.inject.} = BlockPool.init(makeTestDB(genState, genBlock))
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pool {.inject.} = AttestationPool.init(blockPool)
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state {.inject.} = loadTailState(blockPool)
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# Slot 0 is a finalized slot - won't be making attestations for it..
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advanceState(state.data)
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body
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suite "Attestation pool processing" & preset():
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## For now just test that we can compile and execute block processing with
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## mock data.
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# Genesis state with minimal number of deposits
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# Genesis state that results in 2 members per committee
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let
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genState = get_genesis_beacon_state(
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makeInitialDeposits(flags = {skipValidation}), 0, Eth1Data(),
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makeInitialDeposits(SLOTS_PER_EPOCH * 2, {skipValidation}), 0, Eth1Data(),
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{skipValidation})
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genBlock = get_initial_beacon_block(genState)
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test "Can add and retrieve simple attestation" & preset():
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var
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blockPool = BlockPool.init(makeTestDB(genState, genBlock))
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pool = AttestationPool.init(blockPool)
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state = blockPool.loadTailState()
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# Slot 0 is a finalized slot - won't be making attestations for it..
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advanceState(state.data)
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withPool:
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let
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# Create an attestation for slot 1!
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crosslink_committees =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation = makeAttestation(
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state.data.data, state.blck.root, crosslink_committees[0].committee[0])
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let
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# Create an attestation for slot 1 signed by the only attester we have!
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crosslink_committees =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation = makeAttestation(
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state.data.data, state.blck.root, crosslink_committees[0].committee[0])
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pool.add(state.data.data, attestation)
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pool.add(state.data.data, attestation)
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for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1:
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advanceState(state.data)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + MIN_ATTESTATION_INCLUSION_DELAY)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + 1)
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# TODO test needs fixing for new attestation validation
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# check:
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# attestations.len == 1
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check:
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attestations.len == 1
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test "Attestations may arrive in any order" & preset():
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var
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blockPool = BlockPool.init(makeTestDB(genState, genBlock))
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pool = AttestationPool.init(blockPool)
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state = blockPool.loadTailState()
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# Slot 0 is a finalized slot - won't be making attestations for it..
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advanceState(state.data)
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withPool:
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let
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# Create an attestation for slot 1!
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cc0 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation0 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[0])
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let
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# Create an attestation for slot 1 signed by the only attester we have!
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crosslink_committees1 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation1 = makeAttestation(
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state.data.data, state.blck.root, crosslink_committees1[0].committee[0])
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advanceState(state.data)
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advanceState(state.data)
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let
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cc1 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation1 = makeAttestation(
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state.data.data, state.blck.root, cc1[0].committee[0])
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let
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crosslink_committees2 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation2 = makeAttestation(
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state.data.data, state.blck.root, crosslink_committees2[0].committee[0])
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# test reverse order
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pool.add(state.data.data, attestation1)
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pool.add(state.data.data, attestation0)
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# test reverse order
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pool.add(state.data.data, attestation2)
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pool.add(state.data.data, attestation1)
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for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1: advanceState(state.data)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + MIN_ATTESTATION_INCLUSION_DELAY)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + 1)
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# TODO test needs fixing for new attestation validation
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# check:
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# attestations.len == 1
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check:
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attestations.len == 1
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test "Attestations should be combined" & preset():
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withPool:
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let
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# Create an attestation for slot 1!
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cc0 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation0 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[0])
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attestation1 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[1])
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pool.add(state.data.data, attestation0)
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pool.add(state.data.data, attestation1)
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for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1: advanceState(state.data)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + 1)
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check:
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attestations.len == 1
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test "Attestations may overlap, bigger first" & preset():
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withPool:
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var
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# Create an attestation for slot 1!
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cc0 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation0 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[0])
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attestation1 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[1])
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attestation0.combine(attestation1, {skipValidation})
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pool.add(state.data.data, attestation0)
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pool.add(state.data.data, attestation1)
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for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1: advanceState(state.data)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + 1)
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check:
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attestations.len == 1
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test "Attestations may overlap, smaller first" & preset():
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withPool:
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var
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# Create an attestation for slot 1!
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cc0 =
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get_crosslink_committees_at_slot(state.data.data, state.data.data.slot)
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attestation0 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[0])
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attestation1 = makeAttestation(
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state.data.data, state.blck.root, cc0[0].committee[1])
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attestation0.combine(attestation1, {skipValidation})
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pool.add(state.data.data, attestation1)
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pool.add(state.data.data, attestation0)
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for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1: advanceState(state.data)
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let attestations = pool.getAttestationsForBlock(
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state.data.data, state.data.data.slot + 1)
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check:
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attestations.len == 1
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