initial attestation aggregation (#769)
* initial attestation aggregation * fix usage of committee index, vs index in committee; uniformly set trailing/following distance; document how the only-broadcast-if mechanism works better and what aggregation already happens, not otherwise sufficiently clear; use correct BlockSlot across epoch boundaries * address inconsistent notion of which slot in past to target for aggregate broadcast; follow 0.11.x aggregate broadcast p2p interface topic * Fix get_slot_signature(...) call after get_domain(...) change required genesis_validators_root * mark all spec references which aren't dealt with in other PRs as v0.11.1 * update two more spec refs to v0.11.1
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@ -5,20 +5,12 @@
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# * Apache v2 license (license terms in the root directory or at http://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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# Have an an aggregated aggregation ready for broadcast at
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# SECONDS_PER_SLOT * 2 / 3, i.e. 2/3 through relevant slot
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# intervals.
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#
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# The other part is arguably part of attestation pool -- the validation's
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# something that should be happing on receipt, not aggregation per se. In
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# that part, check that messages conform -- so, check for each type
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# https://github.com/ethereum/eth2.0-specs/blob/v0.10.1/specs/phase0/p2p-interface.md#topics-and-messages
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# specifies. So by the time this calls attestation pool, all validation's
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# already done.
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#
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# Finally, some of the filtering's libp2p stuff. Consistency checks between
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# topic/message types and GOSSIP_MAX_SIZE -- mostly doesn't belong here, so
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# while TODO, isn't TODO for this module.
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import
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options,
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@ -26,11 +18,7 @@ import
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state_transition_block],
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./attestation_pool, ./beacon_node_types, ./ssz
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# TODO gossipsub validation lives somewhere, maybe here
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# TODO add tests, especially for validation
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# https://github.com/status-im/nim-beacon-chain/issues/122#issuecomment-562479965
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# https://github.com/ethereum/eth2.0-specs/blob/v0.10.1/specs/phase0/validator.md#aggregation-selection
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#aggregation-selection
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func is_aggregator(state: BeaconState, slot: Slot, index: uint64,
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slot_signature: ValidatorSig): bool =
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# TODO index is a CommitteeIndex, aka uint64
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@ -43,34 +31,49 @@ func is_aggregator(state: BeaconState, slot: Slot, index: uint64,
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proc aggregate_attestations*(
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pool: AttestationPool, state: BeaconState, index: uint64,
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privkey: ValidatorPrivKey): Option[AggregateAndProof] =
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privkey: ValidatorPrivKey, trailing_distance: uint64): Option[AggregateAndProof] =
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# TODO alias CommitteeIndex to actual type then convert various uint64's here
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let
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slot = state.slot - 2
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slot_signature = get_slot_signature(state.fork, slot, privkey)
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doAssert state.slot >= trailing_distance
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/p2p-interface.md#configuration
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doAssert trailing_distance <= ATTESTATION_PROPAGATION_SLOT_RANGE
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let
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slot = state.slot - trailing_distance
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slot_signature = get_slot_signature(
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state.fork, state.genesis_validators_root, slot, privkey)
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if slot < 0:
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return none(AggregateAndProof)
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doAssert slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= state.slot
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doAssert state.slot >= slot
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# https://github.com/ethereum/eth2.0-specs/blob/v0.10.1/specs/phase0/validator.md#aggregation-selection
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# TODO performance issue for future, via get_active_validator_indices(...)
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doAssert index < get_committee_count_at_slot(state, slot)
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# TODO for testing purposes, refactor this into the condition check
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# and just calculation
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#aggregation-selection
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if not is_aggregator(state, slot, index, slot_signature):
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return none(AggregateAndProof)
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let attestation_data =
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makeAttestationData(state, slot, index, get_block_root_at_slot(state, slot))
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#attestation-data
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# describes how to construct an attestation, which applies for makeAttestationData(...)
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# TODO this won't actually match anything
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let attestation_data = AttestationData(
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slot: slot,
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index: index,
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beacon_block_root: get_block_root_at_slot(state, slot))
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# https://github.com/ethereum/eth2.0-specs/blob/v0.10.1/specs/phase0/validator.md#construct-aggregate
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for attestation in getAttestationsForBlock(pool, state, slot):
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#construct-aggregate
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# TODO once EV goes in w/ refactoring of getAttestationsForBlock, pull out the getSlot version and use
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# it. This is incorrect.
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for attestation in getAttestationsForBlock(pool, state):
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# getAttestationsForBlock(...) already aggregates
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if attestation.data == attestation_data:
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# https://github.com/ethereum/eth2.0-specs/blob/v0.10.1/specs/phase0/validator.md#aggregateandproof
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#aggregateandproof
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return some(AggregateAndProof(
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aggregator_index: index,
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aggregate: attestation,
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selection_proof: slot_signature))
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# TODO in catch-up mode, we could get here, so probably shouldn't assert
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doAssert false
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none(AggregateAndProof)
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@ -15,7 +15,8 @@ import
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conf, time, state_transition, beacon_chain_db, validator_pool, extras,
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attestation_pool, block_pool, eth2_network, eth2_discovery,
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beacon_node_types, mainchain_monitor, version, ssz, ssz/dynamic_navigator,
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sync_protocol, request_manager, validator_keygen, interop, statusbar
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sync_protocol, request_manager, validator_keygen, interop, statusbar,
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attestation_aggregation
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const
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genesisFile = "genesis.ssz"
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@ -602,6 +603,45 @@ proc verifyFinalization(node: BeaconNode, slot: Slot) =
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node.blockPool.finalizedHead.blck.slot.compute_epoch_at_slot()
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doAssert finalizedEpoch + 2 == epoch
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proc broadcastAggregatedAttestations(
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node: BeaconNode, state: auto, head: var auto, slot: Slot,
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trailing_distance: uint64) =
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# The index is via a
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# locally attested validator. Unlike in handleAttestations(...) there's a
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# single one at most per slot (because that's how aggregation attestation
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# works), so the machinery that has to handle looping across, basically a
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# set of locally attached validators is in principle not necessary, but a
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# way to organize this. Then the private key for that validator should be
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# the corresponding one -- whatver they are, they match.
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let
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bs = BlockSlot(blck: head, slot: slot)
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committees_per_slot = get_committee_count_at_slot(state, slot)
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var cache = get_empty_per_epoch_cache()
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for committee_index in 0'u64..<committees_per_slot:
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let
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committee = get_beacon_committee(state, slot, committee_index, cache)
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for index_in_committee, validatorIdx in committee:
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let validator = node.getAttachedValidator(state, validatorIdx)
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if validator != nil:
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# This is slightly strange/inverted control flow, since really it's
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# going to happen once per slot, but this is the best way to get at
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# the validator index and private key pair. TODO verify it only has
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# one isSome() with test.
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let option_aggregateandproof =
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aggregate_attestations(node.attestationPool, state,
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committee_index,
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# TODO https://github.com/status-im/nim-beacon-chain/issues/545
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# this assumes in-process private keys
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validator.privKey,
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trailing_distance)
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# Don't broadcast when, e.g., this node isn't an aggregator
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if option_aggregateandproof.isSome:
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node.network.broadcast(
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topicAggregateAndProof, option_aggregateandproof.get)
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proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, async.} =
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## Called at the beginning of a slot - usually every slot, but sometimes might
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## skip a few in case we're running late.
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@ -697,7 +737,7 @@ proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, asyn
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var head = node.updateHead()
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# TODO is the slot of the clock or the head block more interestion? provide
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# TODO is the slot of the clock or the head block more interesting? provide
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# rationale in comment
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beacon_head_slot.set slot.int64
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@ -762,11 +802,12 @@ proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, asyn
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# with any clock discrepancies once only, at the start of slot timer
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# processing..
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# https://github.com/ethereum/eth2.0-specs/blob/v0.9.4/specs/validator/0_beacon-chain-validator.md#attesting
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# A validator should create and broadcast the attestation to the
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# associated attestation subnet one-third of the way through the slot
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# during which the validator is assigned―that is, SECONDS_PER_SLOT / 3
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# seconds after the start of slot.
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#attesting
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# A validator should create and broadcast the attestation to the associated
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# attestation subnet when either (a) the validator has received a valid
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# block from the expected block proposer for the assigned slot or
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# (b) one-third of the slot has transpired (`SECONDS_PER_SLOT / 3` seconds
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# after the start of slot) -- whichever comes first.
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let
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attestationStart = node.beaconClock.fromNow(slot)
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thirdSlot = seconds(int64(SECONDS_PER_SLOT)) div 3
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@ -788,6 +829,25 @@ proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, asyn
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handleAttestations(node, head, slot)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.1/specs/phase0/validator.md#broadcast-aggregate
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# If the validator is selected to aggregate (is_aggregator), then they
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# broadcast their best aggregate as a SignedAggregateAndProof to the global
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# aggregate channel (beacon_aggregate_and_proof) two-thirds of the way
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# through the slot-that is, SECONDS_PER_SLOT * 2 / 3 seconds after the start
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# of slot.
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if slot > 2:
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const TRAILING_DISTANCE = 1
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let aggregationSlot = slot - TRAILING_DISTANCE
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var aggregationHead = getAncestorAt(head, aggregationSlot)
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let bs = BlockSlot(blck: aggregationHead, slot: aggregationSlot)
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node.blockPool.withState(node.blockPool.tmpState, bs):
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let twoThirdsSlot =
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toBeaconTime(slot, seconds(2*int64(SECONDS_PER_SLOT)) div 3)
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addTimer(saturate(node.beaconClock.fromNow(twoThirdsSlot))) do (p: pointer):
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broadcastAggregatedAttestations(
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node, state, aggregationHead, aggregationSlot, TRAILING_DISTANCE)
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# TODO ... and beacon clock might jump here also. sigh.
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let
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nextSlotStart = saturate(node.beaconClock.fromNow(nextSlot))
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@ -13,6 +13,7 @@ const
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topicVoluntaryExits* = "/eth2/voluntary_exit/ssz"
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topicProposerSlashings* = "/eth2/proposer_slashing/ssz"
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topicAttesterSlashings* = "/eth2/attester_slashing/ssz"
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topicAggregateAndProof* = "/eth2/beacon_aggregate_and_proof/ssz"
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# https://github.com/ethereum/eth2.0-specs/blob/v0.11.0/specs/phase0/p2p-interface.md#configuration
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ATTESTATION_SUBNET_COUNT* = 64
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