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nimbus-eth2/beacon_chain/consensus_object_pools/blockchain_dag.nim

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# beacon_chain
# Copyright (c) 2018-2021 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.push raises: [Defect].}
import
std/[options, sequtils, tables, sets],
stew/assign2,
metrics, snappy, chronicles,
../ssz/[ssz_serialization, merkleization], ../beacon_chain_db, ../extras,
../spec/[
crypto, datatypes, digest, helpers, validator, state_transition,
beaconstate],
../beacon_clock,
"."/[block_pools_types, block_quarantine]
from std/times import getTime, `-`
export block_pools_types, helpers
# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#interop-metrics
declareGauge beacon_head_root, "Root of the head block of the beacon chain"
declareGauge beacon_head_slot, "Slot of the head block of the beacon chain"
# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#interop-metrics
declareGauge beacon_finalized_epoch, "Current finalized epoch" # On epoch transition
declareGauge beacon_finalized_root, "Current finalized root" # On epoch transition
declareGauge beacon_current_justified_epoch, "Current justified epoch" # On epoch transition
declareGauge beacon_current_justified_root, "Current justified root" # On epoch transition
declareGauge beacon_previous_justified_epoch, "Current previously justified epoch" # On epoch transition
declareGauge beacon_previous_justified_root, "Current previously justified root" # On epoch transition
declareCounter beacon_reorgs_total, "Total occurrences of reorganizations of the chain" # On fork choice
declareCounter beacon_state_data_cache_hits, "EpochRef hits"
declareCounter beacon_state_data_cache_misses, "EpochRef misses"
declareCounter beacon_state_rewinds, "State database rewinds"
declareGauge beacon_active_validators, "Number of validators in the active validator set"
declareGauge beacon_pending_deposits, "Number of pending deposits (state.eth1_data.deposit_count - state.eth1_deposit_index)" # On block
declareGauge beacon_processed_deposits_total, "Number of total deposits included on chain" # On block
logScope: topics = "chaindag"
proc putBlock*(
dag: var ChainDAGRef, signedBlock: TrustedSignedBeaconBlock) =
dag.db.putBlock(signedBlock)
proc updateStateData*(
dag: ChainDAGRef, state: var StateData, bs: BlockSlot, save: bool,
cache: var StateCache) {.gcsafe.}
template withState*(
dag: ChainDAGRef, stateData: var StateData, blockSlot: BlockSlot,
body: untyped): untyped =
## Helper template that updates stateData to a particular BlockSlot - usage of
## stateData is unsafe outside of block.
## TODO async transformations will lead to a race where stateData gets updated
## while waiting for future to complete - catch this here somehow?
var cache {.inject.} = StateCache()
updateStateData(dag, stateData, blockSlot, false, cache)
template hashedState(): HashedBeaconState {.inject, used.} = stateData.data
template state(): BeaconState {.inject, used.} = stateData.data.data
template blck(): BlockRef {.inject, used.} = stateData.blck
template root(): Eth2Digest {.inject, used.} = stateData.data.root
body
func parent*(bs: BlockSlot): BlockSlot =
## Return a blockslot representing the previous slot, using the parent block
## if the current slot had a block
if bs.slot == Slot(0):
BlockSlot(blck: nil, slot: Slot(0))
else:
BlockSlot(
blck: if bs.slot > bs.blck.slot: bs.blck else: bs.blck.parent,
slot: bs.slot - 1
)
func parentOrSlot*(bs: BlockSlot): BlockSlot =
## Return a blockslot representing the previous slot, using the parent block
## with the current slot if the current had a block
if bs.blck.isNil():
BlockSlot(blck: nil, slot: Slot(0))
elif bs.slot == bs.blck.slot:
BlockSlot(blck: bs.blck.parent, slot: bs.slot)
else:
BlockSlot(blck: bs.blck, slot: bs.slot - 1)
func get_effective_balances*(state: BeaconState): seq[Gwei] =
## Get the balances from a state as counted for fork choice
result.newSeq(state.validators.len) # zero-init
let epoch = state.get_current_epoch()
for i in 0 ..< result.len:
# All non-active validators have a 0 balance
let validator = unsafeAddr state.validators[i]
if validator[].is_active_validator(epoch):
result[i] = validator[].effective_balance
proc init*(
T: type EpochRef, state: BeaconState, cache: var StateCache,
prevEpoch: EpochRef): T =
let
epoch = state.get_current_epoch()
epochRef = EpochRef(
epoch: epoch,
eth1_data: state.eth1_data,
eth1_deposit_index: state.eth1_deposit_index,
current_justified_checkpoint: state.current_justified_checkpoint,
finalized_checkpoint: state.finalized_checkpoint,
shuffled_active_validator_indices:
cache.get_shuffled_active_validator_indices(state, epoch))
for i in 0'u64..<SLOTS_PER_EPOCH:
let idx = get_beacon_proposer_index(
state, cache, epoch.compute_start_slot_at_epoch() + i)
if idx.isSome():
epochRef.beacon_proposers[i] =
some((idx.get(), state.validators[idx.get].pubkey))
# Validator sets typically don't change between epochs - a more efficient
# scheme could be devised where parts of the validator key set is reused
# between epochs because in a single history, the validator set only
# grows - this however is a trivially implementable compromise.
# The validators root is cached in the state, so we can quickly compare
# it to see if it remains unchanged - effective balances in the validator
# information may however result in a different root, even if the public
# keys are the same
let validators_root = hash_tree_root(state.validators)
template sameKeys(a: openArray[ValidatorPubKey], b: openArray[Validator]): bool =
if a.len != b.len:
false
else:
block:
var ret = true
for i, key in a:
if key != b[i].pubkey:
ret = false
break
ret
if prevEpoch != nil and (
prevEpoch.validator_key_store[0] == validators_root or
sameKeys(prevEpoch.validator_key_store[1][], state.validators.asSeq)):
epochRef.validator_key_store =
(validators_root, prevEpoch.validator_key_store[1])
else:
epochRef.validator_key_store = (
validators_root,
newClone(mapIt(state.validators.toSeq, it.pubkey)))
# When fork choice runs, it will need the effective balance of the justified
# checkpoint - we pre-load the balances here to avoid rewinding the justified
# state later and compress them because not all checkpoints end up being used
# for fork choice - specially during long periods of non-finalization
proc snappyEncode(inp: openArray[byte]): seq[byte] =
try:
snappy.encode(inp)
except CatchableError as err:
raiseAssert err.msg
epochRef.effective_balances_bytes =
snappyEncode(SSZ.encode(
List[Gwei, Limit VALIDATOR_REGISTRY_LIMIT](get_effective_balances(state))))
epochRef
func effective_balances*(epochRef: EpochRef): seq[Gwei] =
try:
SSZ.decode(snappy.decode(epochRef.effective_balances_bytes, uint32.high),
List[Gwei, Limit VALIDATOR_REGISTRY_LIMIT]).toSeq()
except CatchableError as exc:
raiseAssert exc.msg
func updateKeyStores*(epochRef: EpochRef, blck: BlockRef, finalized: BlockRef) =
# Because key stores are additive lists, we can use a newer list whereever an
# older list is expected - all indices in the new list will be valid for the
# old list also
var blck = blck
while blck != nil and blck.slot >= finalized.slot:
for e in blck.epochRefs:
e.validator_key_store = epochRef.validator_key_store
blck = blck.parent
func link*(parent, child: BlockRef) =
doAssert (not (parent.root == Eth2Digest() or child.root == Eth2Digest())),
"blocks missing root!"
doAssert parent.root != child.root, "self-references not allowed"
child.parent = parent
func isAncestorOf*(a, b: BlockRef): bool =
var b = b
var depth = 0
const maxDepth = (100'i64 * 365 * 24 * 60 * 60 div SECONDS_PER_SLOT.int)
while true:
if a == b: return true
# for now, use an assert for block chain length since a chain this long
# indicates a circular reference here..
doAssert depth < maxDepth
depth += 1
if a.slot >= b.slot or b.parent.isNil:
return false
doAssert b.slot > b.parent.slot
b = b.parent
func get_ancestor*(blck: BlockRef, slot: Slot,
maxDepth = 100'i64 * 365 * 24 * 60 * 60 div SECONDS_PER_SLOT.int):
BlockRef =
## https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/fork-choice.md#get_ancestor
## Return the most recent block as of the time at `slot` that not more recent
## than `blck` itself
doAssert not blck.isNil
var blck = blck
var depth = 0
while true:
if blck.slot <= slot:
return blck
if blck.parent.isNil:
return nil
doAssert depth < maxDepth
depth += 1
blck = blck.parent
func atSlot*(blck: BlockRef, slot: Slot): BlockSlot =
## Return a BlockSlot at a given slot, with the block set to the closest block
## available. If slot comes from before the block, a suitable block ancestor
## will be used, else blck is returned as if all slots after it were empty.
## This helper is useful when imagining what the chain looked like at a
## particular moment in time, or when imagining what it will look like in the
## near future if nothing happens (such as when looking ahead for the next
## block proposal)
BlockSlot(blck: blck.get_ancestor(slot), slot: slot)
func atEpochStart*(blck: BlockRef, epoch: Epoch): BlockSlot =
## Return the BlockSlot corresponding to the first slot in the given epoch
atSlot(blck, epoch.compute_start_slot_at_epoch)
func atEpochEnd*(blck: BlockRef, epoch: Epoch): BlockSlot =
## Return the BlockSlot corresponding to the last slot in the given epoch
atSlot(blck, (epoch + 1).compute_start_slot_at_epoch - 1)
func epochAncestor*(blck: BlockRef, epoch: Epoch): BlockSlot =
## The state transition works by storing information from blocks in a
## "working" area until the epoch transition, then batching work collected
## during the epoch. Thus, last block in the ancestor epochs is the block
## that has an impact on epoch currently considered.
##
## This function returns a BlockSlot pointing to that epoch boundary, ie the
## boundary where the last block has been applied to the state and epoch
## processing has been done - we will store epoch caches in that particular
## block so that any block in the dag that needs it can find it easily. In
## particular, if empty slot processing is done, there may be multiple epoch
## caches found there.
var blck = blck
while blck.slot.epoch >= epoch and not blck.parent.isNil:
blck = blck.parent
blck.atEpochStart(epoch)
func findEpochRef*(blck: BlockRef, epoch: Epoch): EpochRef = # may return nil!
let ancestor = blck.epochAncestor(epoch)
doAssert ancestor.blck != nil
for epochRef in ancestor.blck.epochRefs:
if epochRef.epoch == epoch:
return epochRef
proc loadStateCache*(cache: var StateCache, blck: BlockRef, epoch: Epoch) =
# When creating a state cache, we want the current and the previous epoch
# information to be preloaded as both of these are used in state transition
# functions
template load(e: Epoch) =
if epoch notin cache.shuffled_active_validator_indices:
let epochRef = blck.findEpochRef(epoch)
if epochRef != nil:
cache.shuffled_active_validator_indices[epochRef.epoch] =
epochRef.shuffled_active_validator_indices
if epochRef.epoch == epoch:
for i, idx in epochRef.beacon_proposers:
cache.beacon_proposer_indices[
epoch.compute_start_slot_at_epoch + i] =
if idx.isSome: some(idx.get()[0]) else: none(ValidatorIndex)
load(epoch)
if epoch > 0:
load(epoch - 1)
func init(T: type BlockRef, root: Eth2Digest, slot: Slot): BlockRef =
BlockRef(
root: root,
slot: slot
)
func init*(T: type BlockRef, root: Eth2Digest, blck: SomeBeaconBlock): BlockRef =
BlockRef.init(root, blck.slot)
proc init*(T: type ChainDAGRef,
preset: RuntimePreset,
db: BeaconChainDB,
updateFlags: UpdateFlags = {}): ChainDAGRef =
# TODO we require that the db contains both a head and a tail block -
# asserting here doesn't seem like the right way to go about it however..
let
tailBlockRoot = db.getTailBlock()
headBlockRoot = db.getHeadBlock()
doAssert tailBlockRoot.isSome(), "Missing tail block, database corrupt?"
doAssert headBlockRoot.isSome(), "Missing head block, database corrupt?"
let
tailRoot = tailBlockRoot.get()
tailBlock = db.getBlock(tailRoot).get()
tailRef = BlockRef.init(tailRoot, tailBlock.message)
headRoot = headBlockRoot.get()
let genesisRef = if tailBlock.message.slot == GENESIS_SLOT:
tailRef
else:
let
genesisBlockRoot = db.getGenesisBlockRoot()
genesisBlock = db.getBlock(genesisBlockRoot).expect(
"preInit should have initialized the database with a genesis block")
BlockRef.init(genesisBlockRoot, genesisBlock.message)
var
blocks = {tailRef.root: tailRef}.toTable()
headRef: BlockRef
if genesisRef != tailRef:
blocks[genesisRef.root] = genesisRef
if headRoot != tailRoot:
var curRef: BlockRef
for blck in db.getAncestorSummaries(headRoot):
if blck.root == tailRef.root:
doAssert(not curRef.isNil)
link(tailRef, curRef)
curRef = curRef.parent
break
let newRef = BlockRef.init(blck.root, blck.summary.slot)
if curRef == nil:
curRef = newRef
headRef = newRef
else:
link(newRef, curRef)
curRef = curRef.parent
blocks[curRef.root] = curRef
trace "Populating block dag", key = curRef.root, val = curRef
doAssert curRef == tailRef,
"head block does not lead to tail, database corrupt?"
else:
headRef = tailRef
var
cur = headRef.atSlot(headRef.slot)
tmpState = (ref StateData)()
# Now that we have a head block, we need to find the most recent state that
# we have saved in the database
while cur.blck != nil:
let root = db.getStateRoot(cur.blck.root, cur.slot)
if root.isSome():
if db.getState(root.get(), tmpState.data.data, noRollback):
tmpState.data.root = root.get()
tmpState.blck = cur.blck
break
if cur.blck.parent != nil and
cur.blck.slot.epoch != epoch(cur.blck.parent.slot):
# We store the state of the parent block with the epoch processing applied
# in the database!
cur = cur.blck.parent.atEpochStart(cur.blck.slot.epoch)
else:
# Moves back slot by slot, in case a state for an empty slot was saved
cur = cur.parent
if tmpState.blck == nil:
warn "No state found in head history, database corrupt?"
# TODO Potentially we could recover from here instead of crashing - what
# would be a good recovery model?
raiseAssert "No state found in head history, database corrupt?"
let res = ChainDAGRef(
blocks: blocks,
tail: tailRef,
genesis: genesisRef,
db: db,
heads: @[headRef],
headState: tmpState[],
epochRefState: tmpState[],
clearanceState: tmpState[],
tmpState: tmpState[],
# The only allowed flag right now is verifyFinalization, as the others all
# allow skipping some validation.
updateFlags: {verifyFinalization} * updateFlags,
runtimePreset: preset,
)
doAssert res.updateFlags in [{}, {verifyFinalization}]
var cache: StateCache
res.updateStateData(res.headState, headRef.atSlot(headRef.slot), false, cache)
# We presently save states on the epoch boundary - it means that the latest
# state we loaded might be older than head block - nonetheless, it will be
# from the same epoch as the head, thus the finalized and justified slots are
# the same - these only change on epoch boundaries.
# When we start from a snapshot state, the `finalized_checkpoint` in the
# snapshot will point to an even older state, but we trust the tail state
# (the snapshot) to be finalized, hence the `max` expression below.
let finalizedEpoch = max(res.headState.data.data.finalized_checkpoint.epoch,
tailRef.slot.epoch)
res.finalizedHead = headRef.atEpochStart(finalizedEpoch)
res.clearanceState = res.headState
# Pruning metadata
res.lastPrunePoint = res.finalizedHead
info "Block dag initialized",
head = shortLog(headRef),
finalizedHead = shortLog(res.finalizedHead),
tail = shortLog(tailRef),
totalBlocks = blocks.len
res
proc getEpochRef*(dag: ChainDAGRef, blck: BlockRef, epoch: Epoch): EpochRef =
let epochRef = blck.findEpochRef(epoch)
if epochRef != nil:
beacon_state_data_cache_hits.inc
return epochRef
beacon_state_data_cache_misses.inc
let
ancestor = blck.epochAncestor(epoch)
dag.withState(dag.epochRefState, ancestor):
let
prevEpochRef = if dag.tail.slot.epoch >= epoch: nil
else: blck.findEpochRef(epoch - 1)
newEpochRef = EpochRef.init(state, cache, prevEpochRef)
# TODO consider constraining the number of epochrefs per state
if ancestor.blck.slot >= dag.finalizedHead.blck.slot:
# Only cache epoch information for unfinalized blocks - earlier states
# are seldomly used (ie RPC), so no need to cache
ancestor.blck.epochRefs.add newEpochRef
newEpochRef.updateKeyStores(blck.parent, dag.finalizedHead.blck)
newEpochRef
proc getFinalizedEpochRef*(dag: ChainDAGRef): EpochRef =
dag.getEpochRef(dag.finalizedHead.blck, dag.finalizedHead.slot.epoch)
proc getState(
dag: ChainDAGRef, state: var StateData, stateRoot: Eth2Digest,
blck: BlockRef): bool =
let restoreAddr =
# Any restore point will do as long as it's not the object being updated
if unsafeAddr(state) == unsafeAddr(dag.headState):
unsafeAddr dag.tmpState
else:
unsafeAddr dag.headState
func restore(v: var BeaconState) =
assign(v, restoreAddr[].data.data)
if not dag.db.getState(stateRoot, state.data.data, restore):
return false
state.blck = blck
state.data.root = stateRoot
true
func isStateCheckpoint(bs: BlockSlot): bool =
## State checkpoints are the points in time for which we store full state
## snapshots, which later serve as rewind starting points when replaying state
## transitions from database, for example during reorgs.
##
# As a policy, we only store epoch boundary states without the epoch block
# (if it exists) applied - the rest can be reconstructed by loading an epoch
# boundary state and applying the missing blocks.
# We also avoid states that were produced with empty slots only - as such,
# there is only a checkpoint for the first epoch after a block.
# The tail block also counts as a state checkpoint!
(bs.slot == bs.blck.slot and bs.blck.parent == nil) or
(bs.slot.isEpoch and bs.slot.epoch == (bs.blck.slot.epoch + 1))
func stateCheckpoint*(bs: BlockSlot): BlockSlot =
## The first ancestor BlockSlot that is a state checkpoint
var bs = bs
while not isStateCheckPoint(bs):
bs = bs.parentOrSlot
bs
proc getState(dag: ChainDAGRef, state: var StateData, bs: BlockSlot): bool =
## Load a state from the database given a block and a slot - this will first
## lookup the state root in the state root table then load the corresponding
## state, if it exists
if not bs.isStateCheckpoint():
return false # Only state checkpoints are stored - no need to hit DB
if (let stateRoot = dag.db.getStateRoot(bs.blck.root, bs.slot);
stateRoot.isSome()):
return dag.getState(state, stateRoot.get(), bs.blck)
false
proc putState*(dag: ChainDAGRef, state: var StateData) =
# Store a state and its root
logScope:
blck = shortLog(state.blck)
stateSlot = shortLog(state.data.data.slot)
stateRoot = shortLog(state.data.root)
if not isStateCheckpoint(state.blck.atSlot(state.data.data.slot)):
return
if dag.db.containsState(state.data.root):
return
debug "Storing state"
# Ideally we would save the state and the root lookup cache in a single
# transaction to prevent database inconsistencies, but the state loading code
# is resilient against one or the other going missing
dag.db.putState(state.data.root, state.data.data)
# Allow backwards-compatible version rollback with bounded recovery cost
if state.data.data.slot.epoch mod 64 == 0:
dag.db.putStateFull(state.data.root, state.data.data)
dag.db.putStateRoot(state.blck.root, state.data.data.slot, state.data.root)
func getRef*(dag: ChainDAGRef, root: Eth2Digest): BlockRef =
## Retrieve a resolved block reference, if available
dag.blocks.getOrDefault(root, nil)
func getBlockRange*(
dag: ChainDAGRef, startSlot: Slot, skipStep: uint64,
output: var openArray[BlockRef]): Natural =
## This function populates an `output` buffer of blocks
## with a slots ranging from `startSlot` up to, but not including,
## `startSlot + skipStep * output.len`, skipping any slots that don't have
## a block.
##
## Blocks will be written to `output` from the end without gaps, even if
## a block is missing in a particular slot. The return value shows how
## many slots were missing blocks - to iterate over the result, start
## at this index.
##
## If there were no blocks in the range, `output.len` will be returned.
let
requestedCount = output.lenu64
headSlot = dag.head.slot
trace "getBlockRange entered",
head = shortLog(dag.head.root), requestedCount, startSlot, skipStep, headSlot
if startSlot < dag.tail.slot or headSlot <= startSlot or requestedCount == 0:
return output.len # Identical to returning an empty set of block as indicated above
let
runway = uint64(headSlot - startSlot)
# This is the number of blocks that will follow the start block
extraBlocks = min(runway div skipStep, requestedCount - 1)
# If `skipStep` is very large, `extraBlocks` should be 0 from
# the previous line, so `endSlot` will be equal to `startSlot`:
endSlot = startSlot + extraBlocks * skipStep
var
b = dag.head.atSlot(endSlot)
o = output.len
# Process all blocks that follow the start block (may be zero blocks)
for i in 1..extraBlocks:
if b.blck.slot == b.slot:
dec o
output[o] = b.blck
for j in 1..skipStep:
b = b.parent
# We should now be at the start block.
# Like any "block slot", it may be a missing/skipped block:
if b.blck.slot == b.slot:
dec o
output[o] = b.blck
o # Return the index of the first non-nil item in the output
func getBlockBySlot*(dag: ChainDAGRef, slot: Slot): BlockRef =
## Retrieves the first block in the current canonical chain
## with slot number less or equal to `slot`.
dag.head.atSlot(slot).blck
func getBlockByPreciseSlot*(dag: ChainDAGRef, slot: Slot): BlockRef =
## Retrieves a block from the canonical chain with a slot
## number equal to `slot`.
let found = dag.getBlockBySlot(slot)
if found.slot != slot: found else: nil
proc get*(dag: ChainDAGRef, blck: BlockRef): BlockData =
## Retrieve the associated block body of a block reference
doAssert (not blck.isNil), "Trying to get nil BlockRef"
let data = dag.db.getBlock(blck.root)
doAssert data.isSome, "BlockRef without backing data, database corrupt?"
BlockData(data: data.get(), refs: blck)
proc get*(dag: ChainDAGRef, root: Eth2Digest): Option[BlockData] =
## Retrieve a resolved block reference and its associated body, if available
let refs = dag.getRef(root)
if not refs.isNil:
some(dag.get(refs))
else:
none(BlockData)
proc advanceSlots(
dag: ChainDAGRef, state: var StateData, slot: Slot, save: bool,
cache: var StateCache) =
# Given a state, advance it zero or more slots by applying empty slot
# processing - the state must be positions at a slot before or equal to the
# target
doAssert state.data.data.slot <= slot
while state.data.data.slot < slot:
doAssert process_slots(
state.data, state.data.data.slot + 1, cache,
dag.updateFlags),
"process_slots shouldn't fail when state slot is correct"
if save:
dag.putState(state)
proc applyBlock(
dag: ChainDAGRef,
state: var StateData, blck: BlockData, flags: UpdateFlags,
cache: var StateCache): bool =
# Apply a single block to the state - the state must be positioned at the
# parent of the block with a slot lower than the one of the block being
# applied
doAssert state.blck == blck.refs.parent
var statePtr = unsafeAddr state # safe because `restore` is locally scoped
func restore(v: var HashedBeaconState) =
doAssert (addr(statePtr.data) == addr v)
statePtr[] = dag.headState
loadStateCache(cache, blck.refs, blck.data.message.slot.epoch)
let ok = state_transition(
dag.runtimePreset, state.data, blck.data,
cache, flags + dag.updateFlags + {slotProcessed}, restore)
if ok:
state.blck = blck.refs
ok
proc updateStateData*(
dag: ChainDAGRef, state: var StateData, bs: BlockSlot, save: bool,
cache: var StateCache) =
## Rewind or advance state such that it matches the given block and slot -
## this may include replaying from an earlier snapshot if blck is on a
## different branch or has advanced to a higher slot number than slot
## If slot is higher than blck.slot, replay will fill in with empty/non-block
## slots, else it is ignored
# First, see if we're already at the requested block. If we are, also check
# that the state has not been advanced past the desired block - if it has,
# an earlier state must be loaded since there's no way to undo the slot
# transitions
let startTime = Moment.now()
var
ancestors: seq[BlockRef]
cur = bs
found = false
template canAdvance(state: StateData, bs: BlockSlot): bool =
# The block is the same and we're at an early enough slot - the state can
# be used to arrive at the desired blockslot
state.blck == bs.blck and state.data.data.slot <= bs.slot
# First, run a quick check if we can simply apply a few blocks to an in-memory
# state - any in-memory state will be faster than loading from database.
# The limit here how many blocks we apply is somewhat arbitrary but two full
# epochs (might be more slots if there are skips) seems like a good enough
# first guess.
# This happens in particular during startup where we replay blocks
# sequentially to grab their votes.
const RewindBlockThreshold = 64
while ancestors.len < RewindBlockThreshold:
if canAdvance(state, cur):
found = true
break
if canAdvance(dag.headState, cur):
assign(state, dag.headState)
found = true
break
if canAdvance(dag.clearanceState, cur):
assign(state, dag.clearanceState)
found = true
break
if canAdvance(dag.epochRefState, cur):
assign(state, dag.epochRefState)
found = true
break
if cur.slot == cur.blck.slot:
# This is not an empty slot, so the block will need to be applied to
# eventually reach bs
ancestors.add(cur.blck)
if cur.blck.parent == nil:
break
# Moving slot by slot helps find states that were advanced with empty slots
cur = cur.parentOrSlot
# Let's see if we're within a few epochs of the state block - then we can
# simply replay blocks without loading the whole state
if not found:
debug "UpdateStateData cache miss",
bs, stateBlock = state.blck, stateSlot = state.data.data.slot
# Either the state is too new or was created by applying a different block.
# We'll now resort to loading the state from the database then reapplying
# blocks until we reach the desired point in time.
cur = bs
ancestors.setLen(0)
# Look for a state in the database and load it - as long as it cannot be
# found, keep track of the blocks that are needed to reach it from the
# state that eventually will be found
while not dag.getState(state, cur):
# There's no state saved for this particular BlockSlot combination, keep
# looking...
if cur.blck.parent != nil and
cur.blck.slot.epoch != epoch(cur.blck.parent.slot):
# We store the state of the parent block with the epoch processing applied
# in the database - we'll need to apply the block however!
ancestors.add(cur.blck)
cur = cur.blck.parent.atEpochStart(cur.blck.slot.epoch)
else:
if cur.slot == cur.blck.slot:
# This is not an empty slot, so the block will need to be applied to
# eventually reach bs
ancestors.add(cur.blck)
# Moves back slot by slot, in case a state for an empty slot was saved
cur = cur.parent
beacon_state_rewinds.inc()
let
startSlot {.used.} = state.data.data.slot # used in logs below
startRoot {.used.} = state.data.root
# Time to replay all the blocks between then and now
for i in countdown(ancestors.len - 1, 0):
# Because the ancestors are in the database, there's no need to persist them
# again. Also, because we're applying blocks that were loaded from the
# database, we can skip certain checks that have already been performed
# before adding the block to the database.
let ok =
dag.applyBlock(state, dag.get(ancestors[i]), {}, cache)
doAssert ok, "Blocks in database should never fail to apply.."
loadStateCache(cache, bs.blck, bs.slot.epoch)
# ...and make sure to process empty slots as requested
dag.advanceSlots(state, bs.slot, save, cache)
let diff = Moment.now() - startTime
logScope:
blocks = ancestors.len
slots = state.data.data.slot - startSlot
stateRoot = shortLog(state.data.root)
stateSlot = state.data.data.slot
startRoot = shortLog(startRoot)
startSlot
blck = shortLog(bs)
found
diff = shortLog(diff)
if diff >= 1.seconds:
# This might indicate there's a cache that's not in order or a disk that is
# too slow - for now, it's here for investigative purposes and the cutoff
# time might need tuning
info "State replayed"
elif ancestors.len > 0:
debug "State replayed"
else:
trace "State advanced" # Normal case!
proc delState(dag: ChainDAGRef, bs: BlockSlot) =
# Delete state state and mapping for a particular block+slot
if not bs.slot.isEpoch:
return # We only ever save epoch states
if (let root = dag.db.getStateRoot(bs.blck.root, bs.slot); root.isSome()):
dag.db.delState(root.get())
dag.db.delStateRoot(bs.blck.root, bs.slot)
proc pruneBlocksDAG(dag: ChainDAGRef) =
## This prunes the block DAG
## This does NOT prune the cached state checkpoints and EpochRef
## This should be done after a new finalization point is reached
## to invalidate pending blocks or attestations referring
## to a now invalid fork.
##
## This does NOT update the `dag.lastPrunePoint` field.
## as the caches and fork choice can be pruned at a later time.
# Clean up block refs, walking block by block
if dag.lastPrunePoint != dag.finalizedHead:
let start = getTime()
# Finalization means that we choose a single chain as the canonical one -
# it also means we're no longer interested in any branches from that chain
# up to the finalization point
let hlen = dag.heads.len
for i in 0..<hlen:
let n = hlen - i - 1
let head = dag.heads[n]
if dag.finalizedHead.blck.isAncestorOf(head):
continue
var cur = head.atSlot(head.slot)
while not cur.blck.isAncestorOf(dag.finalizedHead.blck):
# TODO there may be more empty states here: those that have a slot
# higher than head.slot and those near the branch point - one
# needs to be careful though because those close to the branch
# point should not necessarily be cleaned up
dag.delState(cur) # TODO: should we move that disk I/O to `onSlotEnd`
if cur.blck.slot == cur.slot:
dag.blocks.del(cur.blck.root)
dag.db.delBlock(cur.blck.root)
if cur.blck.parent.isNil:
break
cur = cur.parentOrSlot
dag.heads.del(n)
let stop = getTime()
let dur = stop - start
debug "Pruned the blockchain DAG",
currentCandidateHeads = dag.heads.len,
dagPruningDuration = dur
func needStateCachesAndForkChoicePruning*(dag: ChainDAGRef): bool =
dag.lastPrunePoint != dag.finalizedHead
proc pruneStateCachesDAG*(dag: ChainDAGRef) =
## This prunes the cached state checkpoints and EpochRef
## This does NOT prune the state associated with invalidated blocks on a fork
## They are pruned via `pruneBlocksDAG`
##
## This updates the `dag.lastPrunePoint` variable
doAssert dag.needStateCachesAndForkChoicePruning()
let startState = getTime()
block: # Remove states, walking slot by slot
# We remove all state checkpoints that come _before_ the current finalized
# head, as we might frequently be asked to replay states from the
# finalized checkpoint and onwards (for example when validating blocks and
# attestations)
var
cur = dag.finalizedHead.stateCheckpoint.parentOrSlot
prev = dag.lastPrunePoint.stateCheckpoint.parentOrSlot
while cur.blck != nil and cur != prev:
# TODO This is a quick fix to prune some states from the database, but
# not all, pending a smarter storage - the downside of pruning these
# states is that certain rewinds will take longer
# After long periods of non-finalization, it can also take some time to
# release all these states!
if cur.slot.epoch mod 32 != 0 and cur.slot != dag.tail.slot:
dag.delState(cur)
cur = cur.parentOrSlot
let stopState = getTime()
let durState = stopState - startState
let startEpochRef = getTime()
block: # Clean up old EpochRef instances
# After finalization, we can clear up the epoch cache and save memory -
# it will be recomputed if needed
# TODO don't store recomputed pre-finalization epoch refs
var tmp = dag.finalizedHead.blck
while tmp != dag.lastPrunePoint.blck:
# leave the epoch cache in the last block of the epoch..
tmp = tmp.parent
if tmp.parent != nil:
tmp.parent.epochRefs = @[]
let stopEpochRef = getTime()
let durEpochRef = stopEpochRef - startEpochRef
dag.lastPrunePoint = dag.finalizedHead
debug "Pruned the state checkpoints and DAG caches.",
statePruningDur = durState,
epochRefPruningDur = durEpochRef
proc updateHead*(
dag: ChainDAGRef,
newHead: BlockRef,
quarantine: var QuarantineRef) =
## Update what we consider to be the current head, as given by the fork
## choice.
##
## The choice of head affects the choice of finalization point - the order
## of operations naturally becomes important here - after updating the head,
## blocks that were once considered potential candidates for a tree will
## now fall from grace, or no longer be considered resolved.
doAssert not newHead.isNil()
doAssert not newHead.parent.isNil() or newHead.slot <= dag.tail.slot
logScope:
newHead = shortLog(newHead)
if dag.head == newHead:
trace "No head block update"
return
let
lastHead = dag.head
# Start off by making sure we have the right state - updateStateData will try
# to use existing in-memory states to make this smooth
var cache: StateCache
updateStateData(
dag, dag.headState, newHead.atSlot(newHead.slot), false, cache)
dag.db.putHeadBlock(newHead.root)
let
finalizedHead = newHead.atEpochStart(
dag.headState.data.data.finalized_checkpoint.epoch)
doAssert (not finalizedHead.blck.isNil),
"Block graph should always lead to a finalized block"
if not lastHead.isAncestorOf(newHead):
notice "Updated head block with chain reorg",
lastHead = shortLog(lastHead),
headParent = shortLog(newHead.parent),
stateRoot = shortLog(dag.headState.data.root),
headBlock = shortLog(dag.headState.blck),
stateSlot = shortLog(dag.headState.data.data.slot),
justified = shortLog(dag.headState.data.data.current_justified_checkpoint),
finalized = shortLog(dag.headState.data.data.finalized_checkpoint)
# A reasonable criterion for "reorganizations of the chain"
quarantine.clearQuarantine()
beacon_reorgs_total.inc()
else:
debug "Updated head block",
stateRoot = shortLog(dag.headState.data.root),
headBlock = shortLog(dag.headState.blck),
stateSlot = shortLog(dag.headState.data.data.slot),
justified = shortLog(dag.headState.data.data.current_justified_checkpoint),
finalized = shortLog(dag.headState.data.data.finalized_checkpoint)
# https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#additional-metrics
# both non-negative, so difference can't overflow or underflow int64
beacon_pending_deposits.set(
dag.headState.data.data.eth1_data.deposit_count.toGaugeValue -
dag.headState.data.data.eth1_deposit_index.toGaugeValue)
beacon_processed_deposits_total.set(
dag.headState.data.data.eth1_deposit_index.toGaugeValue)
beacon_head_root.set newHead.root.toGaugeValue
beacon_head_slot.set newHead.slot.toGaugeValue
if lastHead.slot.epoch != newHead.slot.epoch:
# Epoch updated - in theory, these could happen when the wall clock
# changes epoch, even if there is no new block / head, but we'll delay
# updating them until a block confirms the change
beacon_current_justified_epoch.set(
dag.headState.data.data.current_justified_checkpoint.epoch.toGaugeValue)
beacon_current_justified_root.set(
dag.headState.data.data.current_justified_checkpoint.root.toGaugeValue)
beacon_previous_justified_epoch.set(
dag.headState.data.data.previous_justified_checkpoint.epoch.toGaugeValue)
beacon_previous_justified_root.set(
dag.headState.data.data.previous_justified_checkpoint.root.toGaugeValue)
let epochRef = getEpochRef(dag, newHead, newHead.slot.epoch)
beacon_active_validators.set(
epochRef.shuffled_active_validator_indices.lenu64().toGaugeValue)
if finalizedHead != dag.finalizedHead:
notice "Reached new finalization checkpoint",
newFinalizedHead = shortLog(finalizedHead),
oldFinalizedHead = shortLog(dag.finalizedHead)
dag.finalizedHead = finalizedHead
beacon_finalized_epoch.set(
dag.headState.data.data.finalized_checkpoint.epoch.toGaugeValue)
beacon_finalized_root.set(
dag.headState.data.data.finalized_checkpoint.root.toGaugeValue)
dag.pruneBlocksDAG()
proc isInitialized*(T: type ChainDAGRef, db: BeaconChainDB): bool =
let
headBlockRoot = db.getHeadBlock()
tailBlockRoot = db.getTailBlock()
if not (headBlockRoot.isSome() and tailBlockRoot.isSome()):
return false
let
headBlock = db.getBlock(headBlockRoot.get())
tailBlock = db.getBlock(tailBlockRoot.get())
if not (headBlock.isSome() and tailBlock.isSome()):
return false
if not db.containsState(tailBlock.get().message.state_root):
return false
true
proc preInit*(
T: type ChainDAGRef, db: BeaconChainDB,
genesisState, tailState: var BeaconState, tailBlock: SignedBeaconBlock) =
# write a genesis state, the way the ChainDAGRef expects it to be stored in
# database
# TODO probably should just init a block pool with the freshly written
# state - but there's more refactoring needed to make it nice - doing
# a minimal patch for now..
doAssert tailBlock.message.state_root == hash_tree_root(tailState)
notice "New database from snapshot",
blockRoot = shortLog(tailBlock.root),
stateRoot = shortLog(tailBlock.message.state_root),
fork = tailState.fork,
validators = tailState.validators.len()
db.putState(tailState)
db.putBlock(tailBlock)
db.putTailBlock(tailBlock.root)
db.putHeadBlock(tailBlock.root)
db.putStateRoot(tailBlock.root, tailState.slot, tailBlock.message.state_root)
if tailState.slot == GENESIS_SLOT:
db.putGenesisBlockRoot(tailBlock.root)
else:
doAssert genesisState.slot == GENESIS_SLOT
db.putState(genesisState)
let genesisBlock = get_initial_beacon_block(genesisState)
db.putBlock(genesisBlock)
db.putStateRoot(genesisBlock.root, GENESIS_SLOT, genesisBlock.message.state_root)
db.putGenesisBlockRoot(genesisBlock.root)
proc setTailState*(dag: ChainDAGRef,
checkpointState: BeaconState,
checkpointBlock: SignedBeaconBlock) =
# TODO(zah)
# Delete all records up to the tail node. If the tail node is not
# in the database, init the dabase in a way similar to `preInit`.
discard
proc getGenesisBlockData*(dag: ChainDAGRef): BlockData =
dag.get(dag.genesis)
proc getGenesisBlockSlot*(dag: ChainDAGRef): BlockSlot =
BlockSlot(blck: dag.genesis, slot: GENESIS_SLOT)
proc getProposer*(
dag: ChainDAGRef, head: BlockRef, slot: Slot):
Option[(ValidatorIndex, ValidatorPubKey)] =
let
epochRef = dag.getEpochRef(head, slot.compute_epoch_at_slot())
slotInEpoch = slot - slot.compute_epoch_at_slot().compute_start_slot_at_epoch()
epochRef.beacon_proposers[slotInEpoch]
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