nimbus-eth2/beacon_chain/nimbus_light_client.nim

# beacon_chain
# Copyright (c) 2022 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.

import
  std/os,
  chronicles, chronicles/chronos_tools, chronos, stew/io2,
  eth/db/kvstore_sqlite3, eth/keys,
  ./eth1/eth1_monitor,
  ./gossip_processing/optimistic_processor,
  ./networking/topic_params,
  ./spec/beaconstate,
  ./spec/datatypes/[phase0, altair, bellatrix],
  "."/[filepath, light_client, light_client_db, nimbus_binary_common, version]

from ./consensus_object_pools/consensus_manager import runForkchoiceUpdated
from ./gossip_processing/block_processor import newExecutionPayload
from ./gossip_processing/eth2_processor import toValidationResult

# this needs to be global, so it can be set in the Ctrl+C signal handler
var globalRunning = true

programMain:
  ## Ctrl+C handling
  proc controlCHandler() {.noconv.} =
    when defined(windows):
      # workaround for https://github.com/nim-lang/Nim/issues/4057
      try:
        setupForeignThreadGc()
      except Exception as exc: raiseAssert exc.msg # shouldn't happen
    notice "Shutting down after having received SIGINT"
    globalRunning = false
  try:
    setControlCHook(controlCHandler)
  except Exception as exc: # TODO Exception
    warn "Cannot set ctrl-c handler", msg = exc.msg

  var config = makeBannerAndConfig(
    "Nimbus light client " & fullVersionStr, LightClientConf)
  setupLogging(config.logLevel, config.logStdout, config.logFile)

  notice "Launching light client",
    version = fullVersionStr, cmdParams = commandLineParams(), config

  let dbDir = config.databaseDir
  if (let res = secureCreatePath(dbDir); res.isErr):
    fatal "Failed to create create database directory",
      path = dbDir, err = ioErrorMsg(res.error)
    quit 1
  let backend = SqStoreRef.init(dbDir, "nlc").expect("Database OK")
  defer: backend.close()
  let db = backend.initLightClientDB(LightClientDBNames(
    altairHeaders: "altair_lc_headers",
    altairSyncCommittees: "altair_sync_committees")).expect("Database OK")
  defer: db.close()

  let metadata = loadEth2Network(config.eth2Network)
  for node in metadata.bootstrapNodes:
    config.bootstrapNodes.add node
  template cfg(): auto = metadata.cfg

  let
    genesisState =
      try:
        template genesisData(): auto = metadata.genesisData
        newClone(readSszForkedHashedBeaconState(
          cfg, genesisData.toOpenArrayByte(genesisData.low, genesisData.high)))
      except CatchableError as err:
        raiseAssert "Invalid baked-in state: " & err.msg

    beaconClock = BeaconClock.init(
      getStateField(genesisState[], genesis_time))
    getBeaconTime = beaconClock.getBeaconTimeFn()

    genesis_validators_root =
      getStateField(genesisState[], genesis_validators_root)
    forkDigests = newClone ForkDigests.init(cfg, genesis_validators_root)

    genesisBlockRoot = get_initial_beacon_block(genesisState[]).root

    rng = keys.newRng()
    netKeys = getRandomNetKeys(rng[])
    network = createEth2Node(
      rng, config, netKeys, cfg,
      forkDigests, getBeaconTime, genesis_validators_root)

    eth1Monitor =
      if config.web3Urls.len > 0:
        let res = Eth1Monitor.init(
          cfg,
          metadata.depositContractDeployedAt,
          db = nil,
          getBeaconTime,
          config.web3Urls,
          metadata.eth1Network,
          forcePolling = false,
          rng[].loadJwtSecret(config, allowCreate = false),
          # TTD is not relevant for the light client, so it's safe
          # to assume that the TTD has been reached.
          ttdReached = true)
        waitFor res.ensureDataProvider()
        res
      else:
        nil

    optimisticHandler = proc(signedBlock: ForkedMsgTrustedSignedBeaconBlock):
        Future[void] {.async.} =
      notice "New LC optimistic block",
        opt = signedBlock.toBlockId(),
        wallSlot = getBeaconTime().slotOrZero
      withBlck(signedBlock):
        when stateFork >= BeaconStateFork.Bellatrix:
          if blck.message.is_execution_block:
            template payload(): auto = blck.message.body.execution_payload

            if eth1Monitor != nil and not payload.block_hash.isZero:
              await eth1Monitor.ensureDataProvider()

              # engine_newPayloadV1
              discard await eth1Monitor.newExecutionPayload(payload)

              # engine_forkchoiceUpdatedV1
              discard await eth1Monitor.runForkchoiceUpdated(
                headBlockRoot = payload.block_hash,
                safeBlockRoot = payload.block_hash,  # stub value
                finalizedBlockRoot = ZERO_HASH)
        else: discard
    optimisticProcessor = initOptimisticProcessor(
      getBeaconTime, optimisticHandler)

    lightClient = createLightClient(
      network, rng, config, cfg, forkDigests, getBeaconTime,
      genesis_validators_root, LightClientFinalizationMode.Optimistic)

  info "Listening to incoming network requests"
  network.initBeaconSync(cfg, forkDigests, genesisBlockRoot, getBeaconTime)
  network.addValidator(
    getBeaconBlocksTopic(forkDigests.phase0),
    proc (signedBlock: phase0.SignedBeaconBlock): ValidationResult =
      toValidationResult(
        optimisticProcessor.processSignedBeaconBlock(signedBlock)))
  network.addValidator(
    getBeaconBlocksTopic(forkDigests.altair),
    proc (signedBlock: altair.SignedBeaconBlock): ValidationResult =
      toValidationResult(
        optimisticProcessor.processSignedBeaconBlock(signedBlock)))
  network.addValidator(
    getBeaconBlocksTopic(forkDigests.bellatrix),
    proc (signedBlock: bellatrix.SignedBeaconBlock): ValidationResult =
      toValidationResult(
        optimisticProcessor.processSignedBeaconBlock(signedBlock)))
  lightClient.installMessageValidators()
  waitFor network.startListening()
  waitFor network.start()

  proc onFinalizedHeader(
      lightClient: LightClient, finalizedHeader: BeaconBlockHeader) =
    info "New LC finalized header",
      finalized_header = shortLog(finalizedHeader)

    let
      period = finalizedHeader.slot.sync_committee_period
      syncCommittee = lightClient.finalizedSyncCommittee.expect("Bootstrap OK")
    db.putSyncCommittee(period, syncCommittee)
    db.putLatestFinalizedHeader(finalizedHeader)

  proc onOptimisticHeader(
      lightClient: LightClient, optimisticHeader: BeaconBlockHeader) =
    info "New LC optimistic header",
      optimistic_header = shortLog(optimisticHeader)
    optimisticProcessor.setOptimisticHeader(optimisticHeader)

  lightClient.onFinalizedHeader = onFinalizedHeader
  lightClient.onOptimisticHeader = onOptimisticHeader
  lightClient.trustedBlockRoot = some config.trustedBlockRoot

  let latestHeader = db.getLatestFinalizedHeader()
  if latestHeader.isOk:
    let
      period = latestHeader.get.slot.sync_committee_period
      syncCommittee = db.getSyncCommittee(period)
    if syncCommittee.isErr:
      error "LC store lacks sync committee", finalized_header = latestHeader.get
    else:
      lightClient.resetToFinalizedHeader(latestHeader.get, syncCommittee.get)

  # Full blocks gossip is required to portably drive an EL client:
  # - EL clients may not sync when only driven with `forkChoiceUpdated`,
  #   e.g., Geth: "Forkchoice requested unknown head"
  # - `newPayload` requires the full `ExecutionPayload` (most of block content)
  # - `ExecutionPayload` block root is not available in `BeaconBlockHeader`,
  #   so won't be exchanged via light client gossip
  #
  # Future `ethereum/consensus-specs` versions may remove need for full blocks.
  # Therefore, this current mechanism is to be seen as temporary; it is not
  # optimized for reducing code duplication, e.g., with `nimbus_beacon_node`.

  func isSynced(wallSlot: Slot): bool =
    # Check whether light client is used
    let optimisticHeader = lightClient.optimisticHeader.valueOr:
      return false

    # Check whether light client has synced sufficiently close to wall slot
    const maxAge = 2 * SLOTS_PER_EPOCH
    if optimisticHeader.slot < max(wallSlot, maxAge.Slot) - maxAge:
      return false

    true

  func shouldSyncOptimistically(wallSlot: Slot): bool =
    # Check whether an EL is connected
    if eth1Monitor == nil:
      return false

    isSynced(wallSlot)

  var blocksGossipState: GossipState = {}
  proc updateBlocksGossipStatus(slot: Slot) =
    let
      isBehind = not shouldSyncOptimistically(slot)

      targetGossipState = getTargetGossipState(
        slot.epoch, cfg.ALTAIR_FORK_EPOCH, cfg.BELLATRIX_FORK_EPOCH,
        cfg.CAPELLA_FORK_EPOCH, cfg.EIP4844_FORK_EPOCH, isBehind)

    template currentGossipState(): auto = blocksGossipState
    if currentGossipState == targetGossipState:
      return

    if currentGossipState.card == 0 and targetGossipState.card > 0:
      debug "Enabling blocks topic subscriptions",
        wallSlot = slot, targetGossipState
    elif currentGossipState.card > 0 and targetGossipState.card == 0:
      debug "Disabling blocks topic subscriptions",
        wallSlot = slot
    else:
      # Individual forks added / removed
      discard

    let
      newGossipForks = targetGossipState - currentGossipState
      oldGossipForks = currentGossipState - targetGossipState

    for gossipFork in oldGossipForks:
      let forkDigest = forkDigests[].atStateFork(gossipFork)
      network.unsubscribe(getBeaconBlocksTopic(forkDigest))

    for gossipFork in newGossipForks:
      let forkDigest = forkDigests[].atStateFork(gossipFork)
      network.subscribe(
        getBeaconBlocksTopic(forkDigest), blocksTopicParams,
        enableTopicMetrics = true)

    blocksGossipState = targetGossipState

  proc onSlot(wallTime: BeaconTime, lastSlot: Slot) =
    let
      wallSlot = wallTime.slotOrZero()
      expectedSlot = lastSlot + 1
      delay = wallTime - expectedSlot.start_beacon_time()

      finalizedHeader = lightClient.finalizedHeader
      optimisticHeader = lightClient.optimisticHeader

      finalizedBid =
        if finalizedHeader.isSome:
          finalizedHeader.get.toBlockId()
        else:
          BlockId(root: genesisBlockRoot, slot: GENESIS_SLOT)
      optimisticBid =
        if optimisticHeader.isSome:
          optimisticHeader.get.toBlockId()
        else:
          BlockId(root: genesisBlockRoot, slot: GENESIS_SLOT)

      syncStatus =
        if optimisticHeader.isNone:
          "bootstrapping(" & $config.trustedBlockRoot & ")"
        elif not isSynced(wallSlot):
          "syncing"
        else:
          "synced"

    info "Slot start",
      slot = shortLog(wallSlot),
      epoch = shortLog(wallSlot.epoch),
      sync = syncStatus,
      peers = len(network.peerPool),
      head = shortLog(optimisticBid),
      finalized = shortLog(finalizedBid),
      delay = shortLog(delay)

  proc runOnSlotLoop() {.async.} =
    var
      curSlot = getBeaconTime().slotOrZero()
      nextSlot = curSlot + 1
      timeToNextSlot = nextSlot.start_beacon_time() - getBeaconTime()
    while true:
      await sleepAsync(timeToNextSlot)

      let
        wallTime = getBeaconTime()
        wallSlot = wallTime.slotOrZero()

      onSlot(wallTime, curSlot)

      curSlot = wallSlot
      nextSlot = wallSlot + 1
      timeToNextSlot = nextSlot.start_beacon_time() - getBeaconTime()

  var nextExchangeTransitionConfTime = Moment.now + chronos.seconds(60)
  proc onSecond(time: Moment) =
    let wallSlot = getBeaconTime().slotOrZero()

    # engine_exchangeTransitionConfigurationV1
    if time > nextExchangeTransitionConfTime and eth1Monitor != nil:
      nextExchangeTransitionConfTime = time + chronos.seconds(45)
      if wallSlot.epoch >= cfg.BELLATRIX_FORK_EPOCH:
        traceAsyncErrors eth1Monitor.exchangeTransitionConfiguration()

    if checkIfShouldStopAtEpoch(wallSlot, config.stopAtEpoch):
      quit(0)

    updateBlocksGossipStatus(wallSlot + 1)
    lightClient.updateGossipStatus(wallSlot + 1)

  proc runOnSecondLoop() {.async.} =
    let sleepTime = chronos.seconds(1)
    while true:
      let start = chronos.now(chronos.Moment)
      await chronos.sleepAsync(sleepTime)
      let afterSleep = chronos.now(chronos.Moment)
      let sleepTime = afterSleep - start
      onSecond(start)
      let finished = chronos.now(chronos.Moment)
      let processingTime = finished - afterSleep
      trace "onSecond task completed", sleepTime, processingTime

  onSecond(Moment.now())
  lightClient.start()

  asyncSpawn runOnSlotLoop()
  asyncSpawn runOnSecondLoop()
  while globalRunning:
    poll()

  notice "Exiting light client"