359 lines
14 KiB
Nim
359 lines
14 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2020 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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{.push raises: [Defect].}
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import
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# Standard libraries
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std/[algorithm, deques, sequtils, sets, tables, options],
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# Status libraries
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chronicles, stew/[byteutils], json_serialization/std/sets as jsonSets,
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# Internal
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./spec/[beaconstate, datatypes, crypto, digest, helpers],
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./block_pools/[spec_cache, chain_dag, clearance], ./beacon_node_types,
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./fork_choice/fork_choice
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export beacon_node_types, sets
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logScope: topics = "attpool"
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proc init*(T: type AttestationPool, chainDag: ChainDAGRef, quarantine: QuarantineRef): T =
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## Initialize an AttestationPool from the chainDag `headState`
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## The `finalized_root` works around the finalized_checkpoint of the genesis block
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## holding a zero_root.
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# TODO chainDag/quarantine are only used when resolving orphaned attestations - they
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# should probably be removed as a dependency of AttestationPool (or some other
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# smart refactoring)
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chainDag.withState(chainDag.tmpState, chainDag.finalizedHead):
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var forkChoice = initForkChoice(
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chainDag.tmpState,
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).get()
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# Feed fork choice with unfinalized history - during startup, block pool only
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# keeps track of a single history so we just need to follow it
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doAssert chainDag.heads.len == 1, "Init only supports a single history"
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var blocks: seq[BlockRef]
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var cur = chainDag.head
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while cur != chainDag.finalizedHead.blck:
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blocks.add cur
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cur = cur.parent
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for blck in reversed(blocks):
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chainDag.withState(chainDag.tmpState, blck.atSlot(blck.slot)):
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debug "Preloading fork choice with block",
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block_root = shortlog(blck.root),
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parent_root = shortlog(blck.parent.root),
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justified_epoch = state.current_justified_checkpoint.epoch,
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finalized_epoch = state.finalized_checkpoint.epoch,
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slot = blck.slot
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let status =
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forkChoice.process_block(
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chainDag, state, blck, chainDag.get(blck).data.message, blck.slot)
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doAssert status.isOk(), "Error in preloading the fork choice: " & $status.error
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info "Fork choice initialized",
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justified_epoch = chainDag.headState.data.data.current_justified_checkpoint.epoch,
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finalized_epoch = chainDag.headState.data.data.finalized_checkpoint.epoch,
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finalized_root = shortlog(chainDag.finalizedHead.blck.root)
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T(
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chainDag: chainDag,
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quarantine: quarantine,
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unresolved: initTable[Eth2Digest, UnresolvedAttestation](),
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forkChoice: forkChoice
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)
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func processAttestation(
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pool: var AttestationPool, participants: HashSet[ValidatorIndex],
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block_root: Eth2Digest, target_epoch: Epoch) =
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# Add attestation votes to fork choice
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for validator in participants:
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pool.forkChoice.process_attestation(validator, block_root, target_epoch)
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func addUnresolved(pool: var AttestationPool, attestation: Attestation) =
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pool.unresolved[attestation.data.beacon_block_root] =
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UnresolvedAttestation(
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attestation: attestation,
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)
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func candidateIdx(pool: AttestationPool, slot: Slot): Option[uint64] =
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if slot >= pool.startingSlot and
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slot < (pool.startingSlot + pool.candidates.lenu64):
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some(slot mod pool.candidates.lenu64)
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else:
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none(uint64)
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proc updateCurrent(pool: var AttestationPool, wallSlot: Slot) =
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if wallSlot + 1 < pool.candidates.lenu64:
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return
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if pool.startingSlot + pool.candidates.lenu64 - 1 > wallSlot:
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error "Current slot older than attestation pool view, clock reset?",
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poolSlot = pool.startingSlot, wallSlot
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return
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# As time passes we'll clear out any old attestations as they are no longer
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# viable to be included in blocks
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let newWallSlot = wallSlot + 1 - pool.candidates.lenu64
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for i in pool.startingSlot..newWallSlot:
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pool.candidates[i.uint64 mod pool.candidates.lenu64] = AttestationsSeen()
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pool.startingSlot = newWallSlot
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proc addResolved(
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pool: var AttestationPool, blck: BlockRef, attestation: Attestation,
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wallSlot: Slot) =
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# Add an attestation whose parent we know
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logScope:
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attestation = shortLog(attestation)
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updateCurrent(pool, wallSlot)
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doAssert blck.root == attestation.data.beacon_block_root
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let candidateIdx = pool.candidateIdx(attestation.data.slot)
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if candidateIdx.isNone:
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debug "Attestation slot out of range",
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startingSlot = pool.startingSlot
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return
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let
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epochRef = pool.chainDag.getEpochRef(blck, attestation.data.target.epoch)
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attestationsSeen = addr pool.candidates[candidateIdx.get]
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validation = Validation(
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aggregation_bits: attestation.aggregation_bits,
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aggregate_signature: attestation.signature)
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participants = get_attesting_indices(
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epochRef, attestation.data, validation.aggregation_bits)
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var found = false
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for a in attestationsSeen.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 validation.aggregation_bits.isSubsetOf(v.aggregation_bits):
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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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trace "Ignoring subset attestation",
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newParticipants = participants
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found = true
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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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trace "Removing subset attestations",
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newParticipants = participants
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a.validations.keepItIf(
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not it.aggregation_bits.isSubsetOf(validation.aggregation_bits))
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a.validations.add(validation)
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pool.processAttestation(
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participants, a.blck.root, attestation.data.target.epoch)
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info "Attestation resolved",
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attestation = shortLog(attestation),
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validations = a.validations.len(),
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blockSlot = shortLog(blck.slot)
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found = true
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break
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if not found:
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attestationsSeen.attestations.add(AttestationEntry(
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data: attestation.data,
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blck: blck,
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validations: @[validation]
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))
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pool.processAttestation(
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participants, blck.root, attestation.data.target.epoch)
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info "Attestation resolved",
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attestation = shortLog(attestation),
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validations = 1,
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blockSlot = shortLog(blck.slot)
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proc addAttestation*(pool: var AttestationPool,
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attestation: Attestation,
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wallSlot: Slot) =
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## Add a verified attestation to the fork choice context
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logScope: pcs = "atp_add_attestation"
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# Fetch the target block or notify the block pool that it's needed
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let blck = pool.chainDag.getOrResolve(
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pool.quarantine,
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attestation.data.beacon_block_root)
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# If the block exist, add it to the fork choice context
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# Otherwise delay until it resolves
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if blck.isNil:
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pool.addUnresolved(attestation)
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return
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pool.addResolved(blck, attestation, wallSlot)
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proc addForkChoice*(pool: var AttestationPool,
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state: BeaconState,
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blckRef: BlockRef,
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blck: BeaconBlock,
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wallSlot: Slot) =
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## Add a verified block to the fork choice context
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let state = pool.forkChoice.process_block(
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pool.chainDag, state, blckRef, blck, wallSlot)
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if state.isErr:
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# TODO If this happens, it is effectively a bug - the BlockRef structure
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# guarantees that the DAG is valid and the state transition should
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# guarantee that the justified and finalized epochs are ok! However,
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# we'll log it for now to avoid crashes
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error "Unexpected error when applying block",
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blck = shortLog(blck), err = state.error
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proc getAttestationsForSlot*(pool: AttestationPool, newBlockSlot: Slot):
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Option[AttestationsSeen] =
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if newBlockSlot < (GENESIS_SLOT + MIN_ATTESTATION_INCLUSION_DELAY):
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debug "Too early for attestations",
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newBlockSlot = shortLog(newBlockSlot)
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return none(AttestationsSeen)
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let
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attestationSlot = newBlockSlot - MIN_ATTESTATION_INCLUSION_DELAY
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candidateIdx = pool.candidateIdx(attestationSlot)
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if candidateIdx.isNone:
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info "No attestations matching the slot range",
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attestationSlot = shortLog(attestationSlot),
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startingSlot = shortLog(pool.startingSlot)
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return none(AttestationsSeen)
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some(pool.candidates[candidateIdx.get()])
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proc getAttestationsForBlock*(pool: AttestationPool,
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state: BeaconState): seq[Attestation] =
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## Retrieve attestations that may be added to a new block at the slot of the
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## given state
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logScope: pcs = "retrieve_attestation"
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# TODO this shouldn't really need state -- it's to recheck/validate, but that
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# should be refactored
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let newBlockSlot = state.slot
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var attestations: seq[AttestationEntry]
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# This isn't maximally efficient -- iterators or other approaches would
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# avoid lots of memory allocations -- but this provides a more flexible
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# base upon which to experiment with, and isn't yet profiling hot-path,
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# while avoiding penalizing slow attesting too much (as, in the spec it
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# is supposed to be available two epochs back; it's not meant as). This
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# isn't a good solution, either -- see the set-packing comment below as
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# one issue. It also creates problems with lots of repeat attestations,
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# as a bunch of synchronized beacon_nodes do almost the opposite of the
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# intended thing -- sure, _blocks_ have to be popular (via attestation)
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# but _attestations_ shouldn't have to be so frequently repeated, as an
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# artifact of this state-free, identical-across-clones choice basis. In
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# addResolved, too, the new attestations get added to the end, while in
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# these functions, it's reading from the beginning, et cetera. This all
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# needs a single unified strategy.
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for i in max(1, newBlockSlot.int64 - ATTESTATION_LOOKBACK.int64) .. newBlockSlot.int64:
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let maybeSlotData = getAttestationsForSlot(pool, i.Slot)
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if maybeSlotData.isSome:
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insert(attestations, maybeSlotData.get.attestations)
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if attestations.len == 0:
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return
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var cache = StateCache()
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for a in attestations:
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var
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/validator.md#construct-attestation
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attestation = Attestation(
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aggregation_bits: a.validations[0].aggregation_bits,
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data: a.data,
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signature: a.validations[0].aggregate_signature
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)
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# TODO what's going on here is that when producing a block, we need to
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# include only such attestations that will not cause block validation
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# to fail. How this interacts with voting and the acceptance of
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# attestations into the pool in general is an open question that needs
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# revisiting - for example, when attestations are added, against which
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# state should they be validated, if at all?
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# TODO we're checking signatures here every time which is very slow and we don't want
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# to include a broken attestation
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if (let v = check_attestation(state, attestation, {}, cache); v.isErr):
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warn "Attestation no longer validates...",
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attestation = shortLog(attestation),
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err = v.error
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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_bits.overlaps(v.aggregation_bits):
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attestation.aggregation_bits.combine(v.aggregation_bits)
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attestation.signature.aggregate(v.aggregate_signature)
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result.add(attestation)
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if result.lenu64 >= MAX_ATTESTATIONS:
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debug "getAttestationsForBlock: returning early after hitting MAX_ATTESTATIONS",
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attestationSlot = newBlockSlot - 1
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return
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proc resolve*(pool: var AttestationPool, wallSlot: Slot) =
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## Check attestations in our unresolved deque
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## if they can be integrated to the fork choice
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logScope: pcs = "atp_resolve"
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var
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done: seq[Eth2Digest]
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resolved: seq[tuple[blck: BlockRef, attestation: Attestation]]
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for k, v in pool.unresolved.mpairs():
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if (let blck = pool.chainDag.getRef(k); not blck.isNil()):
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resolved.add((blck, v.attestation))
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done.add(k)
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elif v.tries > 8:
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done.add(k)
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else:
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inc v.tries
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for k in done:
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pool.unresolved.del(k)
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for a in resolved:
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pool.addResolved(a.blck, a.attestation, wallSlot)
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proc selectHead*(pool: var AttestationPool, wallSlot: Slot): BlockRef =
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let newHead = pool.forkChoice.find_head(wallSlot)
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if newHead.isErr:
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error "Couldn't select head", err = newHead.error
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nil
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else:
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pool.chainDag.getRef(newHead.get())
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proc prune*(pool: var AttestationPool) =
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if (let v = pool.forkChoice.prune(); v.isErr):
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error "Pruning failed", err = v.error() # TODO should never happen
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