nimbus-eth2/beacon_chain/peer_pool.nim

655 lines
24 KiB
Nim

import tables, heapqueue
import chronos
type
PeerType* = enum
None, Incoming, Outgoing
PeerFlags = enum
Acquired, DeleteOnRelease
EventType = enum
NotEmptyEvent, NotFullEvent
PeerItem[T] = object
data: T
peerType: PeerType
flags: set[PeerFlags]
index: int
PeerIndex = object
data: int
cmp: proc(a, b: PeerIndex): bool {.closure, gcsafe.}
PeerScoreCheckCallback*[T] = proc(peer: T): bool {.gcsafe, raises: [Defect].}
PeerPool*[A, B] = ref object
incNotEmptyEvent: AsyncEvent
outNotEmptyEvent: AsyncEvent
incNotFullEvent: AsyncEvent
outNotFullEvent: AsyncEvent
incQueue: HeapQueue[PeerIndex]
outQueue: HeapQueue[PeerIndex]
registry: Table[B, PeerIndex]
storage: seq[PeerItem[A]]
cmp: proc(a, b: PeerIndex): bool {.closure, gcsafe.}
scoreCheck: PeerScoreCheckCallback[A]
maxPeersCount: int
maxIncPeersCount: int
maxOutPeersCount: int
curIncPeersCount: int
curOutPeersCount: int
acqIncPeersCount: int
acqOutPeersCount: int
PeerPoolError* = object of CatchableError
proc `<`*(a, b: PeerIndex): bool =
result = a.cmp(b, a)
proc fireNotEmptyEvent[A, B](pool: PeerPool[A, B],
item: PeerItem[A]) {.inline.} =
if item.peerType == PeerType.Incoming:
pool.incNotEmptyEvent.fire()
elif item.peerType == PeerType.Outgoing:
pool.outNotEmptyEvent.fire()
proc fireNotFullEvent[A, B](pool: PeerPool[A, B],
item: PeerItem[A]) {.inline.} =
if item.peerType == PeerType.Incoming:
pool.incNotFullEvent.fire()
elif item.peerType == PeerType.Outgoing:
pool.outNotFullEvent.fire()
iterator pairs*[A, B](pool: PeerPool[A, B]): (B, A) =
for peerId, peerIdx in pool.registry:
yield (peerId, pool.storage[peerIdx.data].data)
template incomingEvent(eventType: EventType): AsyncEvent =
case eventType
of EventType.NotEmptyEvent:
pool.incNotEmptyEvent
of EventType.NotFullEvent:
pool.incNotFullEvent
template outgoingEvent(eventType: EventType): AsyncEvent =
case eventType
of EventType.NotEmptyEvent:
pool.outNotEmptyEvent
of EventType.NotFullEvent:
pool.outNotFullEvent
proc waitForEvent[A, B](pool: PeerPool[A, B], eventType: EventType,
filter: set[PeerType]) {.async.} =
if filter == {PeerType.Incoming, PeerType.Outgoing} or filter == {}:
var fut1 = incomingEvent(eventType).wait()
var fut2 = outgoingEvent(eventType).wait()
try:
discard await one(fut1, fut2)
if fut1.finished:
if not(fut2.finished):
fut2.cancel()
incomingEvent(eventType).clear()
else:
if not(fut1.finished):
fut1.cancel()
outgoingEvent(eventType).clear()
except CancelledError:
if not(fut1.finished):
fut1.cancel()
if not(fut2.finished):
fut2.cancel()
raise
elif PeerType.Incoming in filter:
await incomingEvent(eventType).wait()
incomingEvent(eventType).clear()
elif PeerType.Outgoing in filter:
await outgoingEvent(eventType).wait()
outgoingEvent(eventType).clear()
proc waitNotEmptyEvent[A, B](pool: PeerPool[A, B],
filter: set[PeerType]): Future[void] =
pool.waitForEvent(EventType.NotEmptyEvent, filter)
proc waitNotFullEvent[A, B](pool: PeerPool[A, B],
filter: set[PeerType]): Future[void] =
pool.waitForEvent(EventType.NotFullEvent, filter)
template getItem[A, B](pool: PeerPool[A, B],
filter: set[PeerType]): ptr PeerItem[A] =
doAssert((len(pool.outQueue) > 0) or (len(pool.incQueue) > 0))
var pindex: int
if filter == {PeerType.Incoming, PeerType.Outgoing}:
if len(pool.outQueue) > 0 and len(pool.incQueue) > 0:
# Don't think `<` is actually `<` here.
if pool.incQueue[0] < pool.outQueue[0]:
inc(pool.acqIncPeersCount)
pindex = pool.incQueue.pop().data
else:
inc(pool.acqOutPeersCount)
pindex = pool.outQueue.pop().data
else:
if len(pool.outQueue) > 0:
inc(pool.acqOutPeersCount)
pindex = pool.outQueue.pop().data
else:
inc(pool.acqIncPeersCount)
pindex = pool.incQueue.pop().data
else:
if PeerType.Outgoing in filter:
inc(pool.acqOutPeersCount)
pindex = pool.outQueue.pop().data
elif PeerType.Incoming in filter:
inc(pool.acqIncPeersCount)
pindex = pool.incQueue.pop().data
addr(pool.storage[pindex])
proc newPeerPool*[A, B](maxPeers = -1, maxIncomingPeers = -1,
maxOutgoingPeers = -1,
scoreCheckCb: PeerScoreCheckCallback[A] = nil): PeerPool[A, B] =
## Create new PeerPool.
##
## ``maxPeers`` - maximum number of peers allowed. All the peers which
## exceeds this number will be rejected (``addPeer()`` procedure will return
## ``false``). By default this number is infinite.
##
## ``maxIncomingPeers`` - maximum number of incoming peers allowed. All the
## incoming peers exceeds this number will be rejected. By default this
## number is infinite.
##
## ``maxOutgoingPeers`` - maximum number of outgoing peers allowed. All the
## outgoing peers exceeds this number will be rejected. By default this
## number if infinite.
##
## ``scoreCheckCb`` - callback which will be called for all released peers.
## If callback procedure returns ``false`` peer will be removed from
## PeerPool.
##
## Please note, that if ``maxPeers`` is positive non-zero value, then equation
## ``maxPeers >= maxIncomingPeers + maxOutgoingPeers`` must be ``true``.
var res = PeerPool[A, B]()
if maxPeers != -1:
doAssert(maxPeers >= maxIncomingPeers + maxOutgoingPeers)
res.maxPeersCount = if maxPeers < 0: high(int)
else: maxPeers
res.maxIncPeersCount = if maxIncomingPeers < 0: high(int)
else: maxIncomingPeers
res.maxOutPeersCount = if maxOutgoingPeers < 0: high(int)
else: maxOutgoingPeers
res.incNotEmptyEvent = newAsyncEvent()
res.outNotEmptyEvent = newAsyncEvent()
res.incNotFullEvent = newAsyncEvent()
res.outNotFullEvent = newAsyncEvent()
res.incQueue = initHeapQueue[PeerIndex]()
res.outQueue = initHeapQueue[PeerIndex]()
res.registry = initTable[B, PeerIndex]()
res.scoreCheck = scoreCheckCb
res.storage = newSeq[PeerItem[A]]()
proc peerCmp(a, b: PeerIndex): bool {.closure, gcsafe.} =
let p1 = res.storage[a.data].data
let p2 = res.storage[b.data].data
result = p1 < p2
res.cmp = peerCmp
result = res
proc len*[A, B](pool: PeerPool[A, B]): int =
## Returns number of registered peers in PeerPool ``pool``. This number
## includes all the peers (acquired and available).
result = len(pool.registry)
proc lenAvailable*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): int {.inline.} =
## Returns number of available peers in PeerPool ``pool`` which satisfies
## filter ``filter``.
if PeerType.Incoming in filter:
result = result + len(pool.incQueue)
if PeerType.Outgoing in filter:
result = result + len(pool.outQueue)
proc lenAcquired*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): int {.inline.} =
## Returns number of acquired peers in PeerPool ``pool`` which satisifies
## filter ``filter``.
if PeerType.Incoming in filter:
result = result + pool.acqIncPeersCount
if PeerType.Outgoing in filter:
result = result + pool.acqOutPeersCount
proc checkPeerScore*[A, B](pool: PeerPool[A, B], peer: A): bool {.inline.} =
## Returns ``true`` if peer passing score check.
if not(isNil(pool.scoreCheck)):
if pool.scoreCheck(peer):
result = true
else:
result = false
else:
result = true
proc deletePeer*[A, B](pool: PeerPool[A, B], peer: A, force = false): bool =
## Remove ``peer`` from PeerPool ``pool``.
##
## Deletion occurs immediately only if peer is available, otherwise it will
## be deleted only when peer will be released. You can change this behavior
## with ``force`` option.
mixin getKey
var key = getKey(peer)
if pool.registry.hasKey(key):
let pindex = pool.registry[key].data
var item = addr(pool.storage[pindex])
if (PeerFlags.Acquired in item[].flags):
if not(force):
item[].flags.incl(PeerFlags.DeleteOnRelease)
else:
if item[].peerType == PeerType.Incoming:
dec(pool.curIncPeersCount)
dec(pool.acqIncPeersCount)
elif item[].peerType == PeerType.Outgoing:
dec(pool.curOutPeersCount)
dec(pool.acqOutPeersCount)
pool.fireNotFullEvent(item[])
# Cleanup storage with default item, and removing key from hashtable.
pool.storage[pindex] = PeerItem[A]()
pool.registry.del(key)
else:
if item[].peerType == PeerType.Incoming:
# If peer is available, then its copy present in heapqueue, so we need
# to remove it.
for i in 0 ..< len(pool.incQueue):
if pool.incQueue[i].data == pindex:
pool.incQueue.del(i)
break
dec(pool.curIncPeersCount)
elif item[].peerType == PeerType.Outgoing:
# If peer is available, then its copy present in heapqueue, so we need
# to remove it.
for i in 0 ..< len(pool.outQueue):
if pool.outQueue[i].data == pindex:
pool.outQueue.del(i)
break
dec(pool.curOutPeersCount)
pool.fireNotFullEvent(item[])
# Cleanup storage with default item, and removing key from hashtable.
pool.storage[pindex] = PeerItem[A]()
pool.registry.del(key)
result = true
proc addPeerImpl[A, B](pool: PeerPool[A, B], peer: A, peerKey: B,
peerType: PeerType): PeerIndex =
proc onPeerClosed(udata: pointer) {.gcsafe.} =
discard pool.deletePeer(peer)
var item = PeerItem[A](data: peer, peerType: peerType,
index: len(pool.storage))
pool.storage.add(item)
var pitem = addr(pool.storage[^1])
let pindex = PeerIndex(data: item.index, cmp: pool.cmp)
pool.registry[peerKey] = pindex
pitem[].data.getFuture().addCallback(onPeerClosed)
result = pindex
proc addPeerNoWait*[A, B](pool: PeerPool[A, B],
peer: A, peerType: PeerType): bool =
## Add peer ``peer`` of type ``peerType`` to PeerPool ``pool``.
##
## Procedure returns ``false`` in case
## * if ``peer`` is already closed.
## * if ``pool`` already has peer ``peer`` inside.
## * if ``pool`` currently has a maximum of peers.
## * if ``pool`` currently has a maximum of `Incoming` or `Outgoing` peers.
##
## Procedure returns ``true`` on success.
mixin getKey, getFuture
if not(pool.checkPeerScore(peer)):
return false
result = false
let peerKey = getKey(peer)
if not(pool.registry.hasKey(peerKey)) and not(peer.getFuture().finished):
if len(pool.registry) < pool.maxPeersCount:
if peerType == PeerType.Incoming:
if pool.curIncPeersCount < pool.maxIncPeersCount:
let pindex = pool.addPeerImpl(peer, peerKey, peerType)
inc(pool.curIncPeersCount)
pool.incQueue.push(pindex)
pool.incNotEmptyEvent.fire()
result = true
elif peerType == PeerType.Outgoing:
if pool.curOutPeersCount < pool.maxOutPeersCount:
let pindex = pool.addPeerImpl(peer, peerKey, peerType)
inc(pool.curOutPeersCount)
pool.outQueue.push(pindex)
pool.outNotEmptyEvent.fire()
result = true
proc addPeer*[A, B](pool: PeerPool[A, B],
peer: A, peerType: PeerType): Future[bool] {.async.} =
## Add peer ``peer`` of type ``peerType`` to PeerPool ``pool``.
##
## This procedure will wait for an empty space in PeerPool ``pool``, if
## PeerPool ``pool`` is full.
##
## Procedure returns ``false`` in case:
## * if ``peer`` is already closed.
## * if ``pool`` already has peer ``peer`` inside.
##
## Procedure returns ``true`` on success.
mixin getKey, getFuture
if not(pool.checkPeerScore(peer)):
return false
var res = false
let peerKey = getKey(peer)
if not(pool.registry.hasKey(peerKey)) and not(peer.getFuture().finished):
while len(pool.registry) >= pool.maxPeersCount:
await pool.waitNotFullEvent({PeerType.Incoming, PeerType.Outgoing})
if peerType == PeerType.Incoming:
while pool.curIncPeersCount >= pool.maxIncPeersCount:
await pool.waitNotFullEvent({peerType})
let pindex = pool.addPeerImpl(peer, peerKey, peerType)
inc(pool.curIncPeersCount)
pool.incQueue.push(pindex)
pool.incNotEmptyEvent.fire()
res = true
elif peerType == PeerType.Outgoing:
while pool.curOutPeersCount >= pool.maxOutPeersCount:
await pool.waitNotFullEvent({peerType})
let pindex = pool.addPeerImpl(peer, peerKey, peerType)
inc(pool.curOutPeersCount)
pool.outQueue.push(pindex)
pool.outNotEmptyEvent.fire()
res = true
result = res
proc addIncomingPeerNoWait*[A, B](pool: PeerPool[A, B],
peer: A): bool {.inline.} =
## Add incoming peer ``peer`` to PeerPool ``pool``.
##
## Returns ``true`` on success.
result = pool.addPeerNoWait(peer, PeerType.Incoming)
proc addOutgoingPeerNoWait*[A, B](pool: PeerPool[A, B],
peer: A): bool {.inline.} =
## Add outgoing peer ``peer`` to PeerPool ``pool``.
##
## Returns ``true`` on success.
result = pool.addPeerNoWait(peer, PeerType.Outgoing)
proc addIncomingPeer*[A, B](pool: PeerPool[A, B],
peer: A): Future[bool] {.inline.} =
## Add incoming peer ``peer`` to PeerPool ``pool``.
##
## Returns ``true`` on success.
result = pool.addPeer(peer, PeerType.Incoming)
proc addOutgoingPeer*[A, B](pool: PeerPool[A, B],
peer: A): Future[bool] {.inline.} =
## Add outgoing peer ``peer`` to PeerPool ``pool``.
##
## Returns ``true`` on success.
result = pool.addPeer(peer, PeerType.Outgoing)
proc acquire*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): Future[A] {.async.} =
## Acquire peer from PeerPool ``pool``, which match the filter ``filter``.
doAssert(filter != {}, "Filter must not be empty")
while true:
var count = 0
if PeerType.Incoming in filter:
count = count + len(pool.incQueue)
if PeerType.Outgoing in filter:
count = count + len(pool.outQueue)
if count == 0:
await pool.waitNotEmptyEvent(filter)
else:
var item = pool.getItem(filter)
doAssert(PeerFlags.Acquired notin item[].flags)
item[].flags.incl(PeerFlags.Acquired)
result = item[].data
break
proc acquireNoWait*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): A =
doAssert(filter != {}, "Filter must not be empty")
var count = 0
if PeerType.Incoming in filter:
count = count + len(pool.incQueue)
if PeerType.Outgoing in filter:
count = count + len(pool.outQueue)
if count < 1:
raise newException(PeerPoolError, "Not enough peers in pool")
var item = pool.getItem(filter)
doAssert(PeerFlags.Acquired notin item[].flags)
item[].flags.incl(PeerFlags.Acquired)
result = item[].data
proc release*[A, B](pool: PeerPool[A, B], peer: A) =
## Release peer ``peer`` back to PeerPool ``pool``
mixin getKey
var key = getKey(peer)
var titem = pool.registry.getOrDefault(key, PeerIndex(data: -1))
if titem.data >= 0:
let pindex = titem.data
var item = addr(pool.storage[pindex])
if PeerFlags.Acquired in item[].flags:
if not(pool.checkPeerScore(peer)):
item[].flags.incl(DeleteOnRelease)
item[].flags.excl(PeerFlags.Acquired)
if PeerFlags.DeleteOnRelease in item[].flags:
if item[].peerType == PeerType.Incoming:
dec(pool.curIncPeersCount)
dec(pool.acqIncPeersCount)
elif item[].peerType == PeerType.Outgoing:
dec(pool.curOutPeersCount)
dec(pool.acqOutPeersCount)
pool.storage[pindex] = PeerItem[A]()
pool.registry.del(key)
else:
if item[].peerType == PeerType.Incoming:
pool.incQueue.push(titem)
dec(pool.acqIncPeersCount)
elif item[].peerType == PeerType.Outgoing:
pool.outQueue.push(titem)
dec(pool.acqOutPeersCount)
pool.fireNotEmptyEvent(item[])
proc release*[A, B](pool: PeerPool[A, B], peers: openarray[A]) {.inline.} =
## Release array of peers ``peers`` back to PeerPool ``pool``.
for item in peers:
pool.release(item)
proc acquire*[A, B](pool: PeerPool[A, B],
number: int,
filter = {PeerType.Incoming,
PeerType.Outgoing}): Future[seq[A]] {.async.} =
## Acquire ``number`` number of peers from PeerPool ``pool``, which match the
## filter ``filter``.
doAssert(filter != {}, "Filter must not be empty")
var peers = newSeq[A]()
try:
if number > 0:
while true:
if len(peers) >= number:
break
var count = 0
if PeerType.Incoming in filter:
count = count + len(pool.incQueue)
if PeerType.Outgoing in filter:
count = count + len(pool.outQueue)
if count == 0:
await pool.waitNotEmptyEvent(filter)
else:
var item = pool.getItem(filter)
doAssert(PeerFlags.Acquired notin item[].flags)
item[].flags.incl(PeerFlags.Acquired)
peers.add(item[].data)
except CancelledError:
# If we got cancelled, we need to return all the acquired peers back to
# pool.
for item in peers:
pool.release(item)
peers.setLen(0)
raise
result = peers
proc acquireNoWait*[A, B](pool: PeerPool[A, B],
number: int,
filter = {PeerType.Incoming,
PeerType.Outgoing}): seq[A] =
## Acquire ``number`` number of peers from PeerPool ``pool``, which match the
## filter ``filter``.
doAssert(filter != {}, "Filter must not be empty")
var peers = newSeq[A]()
var count = 0
if PeerType.Incoming in filter:
count = count + len(pool.incQueue)
if PeerType.Outgoing in filter:
count = count + len(pool.outQueue)
if count < number:
raise newException(PeerPoolError, "Not enough peers in pool")
for i in 0 ..< number:
var item = pool.getItem(filter)
doAssert(PeerFlags.Acquired notin item[].flags)
item[].flags.incl(PeerFlags.Acquired)
peers.add(item[].data)
result = peers
proc acquireIncomingPeer*[A, B](pool: PeerPool[A, B]): Future[A] {.inline.} =
## Acquire single incoming peer from PeerPool ``pool``.
pool.acquire({PeerType.Incoming})
proc acquireOutgoingPeer*[A, B](pool: PeerPool[A, B]): Future[A] {.inline.} =
## Acquire single outgoing peer from PeerPool ``pool``.
pool.acquire({PeerType.Outgoing})
proc acquireIncomingPeers*[A, B](pool: PeerPool[A, B],
number: int): Future[seq[A]] {.inline.} =
## Acquire ``number`` number of incoming peers from PeerPool ``pool``.
pool.acquire(number, {PeerType.Incoming})
proc acquireOutgoingPeers*[A, B](pool: PeerPool[A, B],
number: int): Future[seq[A]] {.inline.} =
## Acquire ``number`` number of outgoing peers from PeerPool ``pool``.
pool.acquire(number, {PeerType.Outgoing})
iterator peers*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): A =
## Iterate over sorted list of peers.
##
## All peers will be sorted by equation `>`(Peer1, Peer2), so biggest values
## will be first.
var sorted = initHeapQueue[PeerIndex]()
for i in 0 ..< len(pool.storage):
if pool.storage[i].peerType in filter:
sorted.push(PeerIndex(data: i, cmp: pool.cmp))
while len(sorted) > 0:
let pindex = sorted.pop().data
yield pool.storage[pindex].data
iterator availablePeers*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): A =
## Iterate over sorted list of available peers.
##
## All peers will be sorted by equation `>`(Peer1, Peer2), so biggest values
## will be first.
var sorted = initHeapQueue[PeerIndex]()
for i in 0 ..< len(pool.storage):
if (PeerFlags.Acquired notin pool.storage[i].flags) and
(pool.storage[i].peerType in filter):
sorted.push(PeerIndex(data: i, cmp: pool.cmp))
while len(sorted) > 0:
let pindex = sorted.pop().data
yield pool.storage[pindex].data
iterator acquiredPeers*[A, B](pool: PeerPool[A, B],
filter = {PeerType.Incoming,
PeerType.Outgoing}): A =
## Iterate over sorted list of acquired (non-available) peers.
##
## All peers will be sorted by equation `>`(Peer1, Peer2), so biggest values
## will be first.
var sorted = initHeapQueue[PeerIndex]()
for i in 0 ..< len(pool.storage):
if (PeerFlags.Acquired in pool.storage[i].flags) and
(pool.storage[i].peerType in filter):
sorted.push(PeerIndex(data: i, cmp: pool.cmp))
while len(sorted) > 0:
let pindex = sorted.pop().data
yield pool.storage[pindex].data
proc `[]`*[A, B](pool: PeerPool[A, B], key: B): A {.inline.} =
## Retrieve peer with key ``key`` from PeerPool ``pool``.
let pindex = pool.registry[key]
result = pool.storage[pindex.data]
proc `[]`*[A, B](pool: var PeerPool[A, B], key: B): var A {.inline.} =
## Retrieve peer with key ``key`` from PeerPool ``pool``.
let pindex = pool.registry[key]
result = pool.storage[pindex.data].data
proc hasPeer*[A, B](pool: PeerPool[A, B], key: B): bool {.inline.} =
## Returns ``true`` if peer with ``key`` present in PeerPool ``pool``.
result = pool.registry.hasKey(key)
proc getOrDefault*[A, B](pool: PeerPool[A, B], key: B): A {.inline.} =
## Retrieves the peer from PeerPool ``pool`` using key ``key``. If peer is
## not present, default initialization value for type ``A`` is returned
## (e.g. 0 for any integer type).
let pindex = pool.registry.getOrDefault(key, PeerIndex(data: -1))
if pindex.data >= 0:
result = pool.storage[pindex.data].data
proc getOrDefault*[A, B](pool: PeerPool[A, B], key: B,
default: A): A {.inline.} =
## Retrieves the peer from PeerPool ``pool`` using key ``key``. If peer is
## not present, default value ``default`` is returned.
let pindex = pool.registry.getOrDefault(key, PeerIndex(data: -1))
if pindex.data >= 0:
result = pool.storage[pindex.data].data
else:
result = default
proc clear*[A, B](pool: PeerPool[A, B]) =
## Performs PeerPool's ``pool`` storage and counters reset.
pool.incQueue.clear()
pool.outQueue.clear()
pool.registry.clear()
for i in 0 ..< len(pool.storage):
pool.storage[i] = PeerItem[A]()
pool.storage.setLen(0)
pool.curIncPeersCount = 0
pool.curOutPeersCount = 0
pool.acqIncPeersCount = 0
pool.acqOutPeersCount = 0
proc clearSafe*[A, B](pool: PeerPool[A, B]) {.async.} =
## Performs "safe" clear. Safe means that it first acquires all the peers
## in PeerPool, and only after that it will reset storage.
var acquired = newSeq[A]()
while len(pool.registry) > len(acquired):
var peers = await pool.acquire(len(pool.registry) - len(acquired))
for item in peers:
acquired.add(item)
pool.clear()
proc setScoreCheck*[A, B](pool: PeerPool[A, B],
scoreCheckCb: PeerScoreCheckCallback[A]) =
## Add ScoreCheck callback.
pool.scoreCheck = scoreCheckCb