@lodestar/beacon-node
Version:
A Typescript implementation of the beacon chain
231 lines • 14.2 kB
JavaScript
import { routes } from "@lodestar/api";
import { getSafeExecutionBlockHash } from "@lodestar/fork-choice";
import { ForkSeq, SLOTS_PER_EPOCH, isForkPostBellatrix } from "@lodestar/params";
import { StateHashTreeRootSource, computeEpochAtSlot, computeTimeAtSlot, isStatePostBellatrix, isStatePostGloas, } from "@lodestar/state-transition";
import { fromHex, isErrorAborted, sleep } from "@lodestar/utils";
import { GENESIS_SLOT, ZERO_HASH_HEX } from "../constants/constants.js";
import { BuilderStatus } from "../execution/builder/http.js";
import { ClockEvent } from "../util/clock.js";
import { isQueueErrorAborted } from "../util/queue/index.js";
import { ForkchoiceCaller } from "./forkChoice/index.js";
import { getPayloadAttributesForSSE, prepareExecutionPayload } from "./produceBlock/produceBlockBody.js";
import { RegenCaller } from "./regen/index.js";
// TODO GLOAS: re-evaluate this timing
/* With 12s slot times, this scheduler will run 4s before the start of each slot (`12 - 0.6667 * 12 = 4`). */
export const PREPARE_NEXT_SLOT_BPS = 6667;
/* We don't want to do more epoch transition than this */
const PREPARE_EPOCH_LIMIT = 1;
/**
* At Bellatrix, if we are responsible for proposing in next slot, we want to prepare payload
* 4s before the start of next slot at PREPARE_NEXT_SLOT_BPS of the current slot.
*
* For all forks, when clock reaches PREPARE_NEXT_SLOT_BPS of slot before an epoch, we want to prepare for the next epoch
* transition from our head so that:
* + validators vote for block head on time through attestation
* + validators propose blocks on time
* + For Bellatrix, to compute proposers of next epoch so that we can prepare new payloads
*
*/
export class PrepareNextSlotScheduler {
chain;
config;
metrics;
logger;
signal;
constructor(chain, config, metrics, logger, signal) {
this.chain = chain;
this.config = config;
this.metrics = metrics;
this.logger = logger;
this.signal = signal;
this.chain.clock.on(ClockEvent.slot, this.prepareForNextSlot);
this.signal.addEventListener("abort", () => {
this.chain.clock.off(ClockEvent.slot, this.prepareForNextSlot);
}, { once: true });
}
/**
* Use clockSlot instead of clockEpoch to schedule the task at more exact time.
*/
prepareForNextSlot = async (clockSlot) => {
const prepareSlot = clockSlot + 1;
const prepareEpoch = computeEpochAtSlot(prepareSlot);
const nextEpoch = computeEpochAtSlot(clockSlot) + 1;
const isEpochTransition = prepareEpoch === nextEpoch;
const fork = this.config.getForkName(prepareSlot);
// Early return if we are pre-genesis
// or we are pre-bellatrix and this is not an epoch transition
if (prepareSlot <= GENESIS_SLOT || (ForkSeq[fork] < ForkSeq.bellatrix && !isEpochTransition)) {
return;
}
try {
// At PREPARE_NEXT_SLOT_BPS (~67%) of the current slot we prepare payload for the next slot
// or precompute epoch transition
await sleep(this.config.getSlotComponentDurationMs(PREPARE_NEXT_SLOT_BPS), this.signal);
// calling updateHead() here before we produce a block to reduce reorg possibility
const headBlock = this.chain.recomputeForkChoiceHead(ForkchoiceCaller.prepareNextSlot);
const { slot: headSlot, blockRoot: headRoot } = headBlock;
// may be updated below if we predict a proposer-boost-reorg
let updatedHead = headBlock;
// PS: previously this was comparing slots, but that gave no leway on the skipped
// slots on epoch bounday. Making it more fluid.
if (prepareSlot - headSlot > PREPARE_EPOCH_LIMIT * SLOTS_PER_EPOCH) {
this.metrics?.precomputeNextEpochTransition.count.inc({ result: "skip" }, 1);
this.logger.debug("Skipping PrepareNextSlotScheduler - head slot is too behind current slot", {
nextEpoch,
headSlot,
clockSlot,
});
return;
}
this.logger.verbose("Running prepareForNextSlot", {
nextEpoch,
prepareSlot,
headSlot,
headRoot,
isEpochTransition,
});
const precomputeEpochTransitionTimer = isEpochTransition
? this.metrics?.precomputeNextEpochTransition.duration.startTimer()
: null;
const start = Date.now();
// No need to wait for this or the clock drift
// Pre Bellatrix: we only do precompute state transition for the last slot of epoch
// For Bellatrix, we always do the `processSlots()` to prepare payload for the next slot
const prepareState = await this.chain.regen.getBlockSlotState(headBlock, prepareSlot,
// the slot 0 of next epoch will likely use this Previous Root Checkpoint state for state transition so we transfer cache here
// the resulting state with cache will be cached in Checkpoint State Cache which is used for the upcoming block processing
// for other slots dontTransferCached=true because we don't run state transition on this state
{ dontTransferCache: !isEpochTransition }, RegenCaller.precomputeEpoch);
if (isForkPostBellatrix(fork)) {
const proposerIndex = prepareState.getBeaconProposer(prepareSlot);
const feeRecipient = this.chain.beaconProposerCache.get(proposerIndex);
let updatedPrepareState = prepareState;
if (feeRecipient) {
// If we are proposing next slot, we need to predict if we can proposer-boost-reorg or not
const proposerHead = this.chain.predictProposerHead(clockSlot);
const { slot: proposerHeadSlot, blockRoot: proposerHeadRoot } = proposerHead;
// If we predict we can reorg, update prepareState with proposer head block
if (proposerHeadRoot !== headRoot || proposerHeadSlot !== headSlot) {
this.logger.verbose("Weak head detected. May build on parent block instead", {
proposerHeadSlot,
proposerHeadRoot,
headSlot,
headRoot,
});
this.metrics?.weakHeadDetected.inc();
updatedPrepareState = await this.chain.regen.getBlockSlotState(proposerHead, prepareSlot,
// only transfer cache if epoch transition because that's the state we will use to stateTransition() the 1st block of epoch
{ dontTransferCache: !isEpochTransition }, RegenCaller.predictProposerHead);
updatedHead = proposerHead;
}
// Update the builder status, if enabled shoot an api call to check status
this.chain.updateBuilderStatus(clockSlot);
if (this.chain.executionBuilder?.status === BuilderStatus.enabled) {
this.chain.executionBuilder.checkStatus().catch((e) => {
this.logger.error("Builder disabled as the check status api failed", { prepareSlot }, e);
});
}
}
if (!isStatePostBellatrix(updatedPrepareState)) {
throw new Error("Expected Bellatrix state for payload attributes");
}
let parentBlockHash;
// Apply parent payload once here as it's reused by EL prep and SSE emit below
let stateAfterParentPayload = updatedPrepareState;
if (isStatePostGloas(updatedPrepareState)) {
if (this.chain.forkChoice.shouldExtendPayload(updatedHead.blockRoot)) {
parentBlockHash = updatedPrepareState.latestExecutionPayloadBid.blockHash;
// Skip applying parent payload unless we're proposing the next slot or have to emit payload_attributes events
if (feeRecipient !== undefined || this.chain.opts.emitPayloadAttributes === true) {
const parentExecutionRequests = await this.chain.getParentExecutionRequests(updatedHead.slot, updatedHead.blockRoot);
stateAfterParentPayload = updatedPrepareState.withParentPayloadApplied(parentExecutionRequests);
}
}
else {
parentBlockHash = updatedPrepareState.latestExecutionPayloadBid.parentBlockHash;
}
}
else {
parentBlockHash = updatedPrepareState.latestExecutionPayloadHeader.blockHash;
}
if (feeRecipient) {
const preparationTime = computeTimeAtSlot(this.config, prepareSlot, this.chain.genesisTime) - Date.now() / 1000;
this.metrics?.blockPayload.payloadAdvancePrepTime.observe(preparationTime);
const safeBlockHash = getSafeExecutionBlockHash(this.chain.forkChoice);
const finalizedBlockHash = this.chain.forkChoice.getFinalizedBlock().executionPayloadBlockHash ?? ZERO_HASH_HEX;
// awaiting here instead of throwing an async call because there is no other task
// left for scheduler and this gives nice semantics to catch and log errors in the
// try/catch wrapper here.
await prepareExecutionPayload(this.chain, this.logger, fork, // State is of execution type
fromHex(updatedHead.blockRoot), parentBlockHash, safeBlockHash, finalizedBlockHash, stateAfterParentPayload, feeRecipient);
this.logger.verbose("PrepareNextSlotScheduler prepared new payload", {
prepareSlot,
proposerIndex,
feeRecipient,
});
}
if (ForkSeq[fork] >= ForkSeq.gloas) {
// Cutoff = slot of the parent of the block we'll actually build on (post-reorg).
// Steady state: cache holds just 2 entries — head (parent for next-slot production)
// and head.parent (proposer-boost-reorg fallback). Anything older is evicted.
const updatedHeadParent = this.chain.forkChoice.getBlockHexDefaultStatus(updatedHead.parentRoot);
if (updatedHeadParent) {
this.chain.seenPayloadEnvelopeInputCache.pruneBelowParent(updatedHeadParent);
}
}
this.computeStateHashTreeRoot(updatedPrepareState, isEpochTransition);
// If emitPayloadAttributes is true emit a SSE payloadAttributes event for
// every slot. Without the flag, only emit the event if we are proposing in the next slot.
if ((feeRecipient || this.chain.opts.emitPayloadAttributes === true) &&
this.chain.emitter.listenerCount(routes.events.EventType.payloadAttributes)) {
const data = getPayloadAttributesForSSE(fork, this.chain, {
prepareState: stateAfterParentPayload,
prepareSlot,
parentBlockRoot: fromHex(updatedHead.blockRoot),
parentBlockHash,
feeRecipient: feeRecipient ?? "0x0000000000000000000000000000000000000000",
});
this.chain.emitter.emit(routes.events.EventType.payloadAttributes, { data, version: fork });
}
}
else {
this.computeStateHashTreeRoot(prepareState, isEpochTransition);
}
// assuming there is no reorg, it caches the checkpoint state & helps avoid doing a full state transition in the next slot
// + when gossip block comes, we need to validate and run state transition
// + if next slot is a skipped slot, it'd help getting target checkpoint state faster to validate attestations
if (isEpochTransition) {
this.metrics?.precomputeNextEpochTransition.count.inc({ result: "success" }, 1);
const previousHits = this.chain.regen.updatePreComputedCheckpoint(headRoot, nextEpoch);
if (previousHits === 0) {
this.metrics?.precomputeNextEpochTransition.waste.inc();
}
this.metrics?.precomputeNextEpochTransition.hits.set(previousHits ?? 0);
this.logger.verbose("Completed PrepareNextSlotScheduler epoch transition", {
nextEpoch,
headSlot,
prepareSlot,
previousHits,
durationMs: Date.now() - start,
});
precomputeEpochTransitionTimer?.();
}
}
catch (e) {
if (!isErrorAborted(e) && !isQueueErrorAborted(e)) {
this.metrics?.precomputeNextEpochTransition.count.inc({ result: "error" }, 1);
this.logger.error("Failed to run prepareForNextSlot", { nextEpoch, isEpochTransition, prepareSlot }, e);
}
}
};
computeStateHashTreeRoot(state, isEpochTransition) {
// cache HashObjects for faster hashTreeRoot() later, especially for computeNewStateRoot() if we need to produce a block at slot 0 of epoch
// see https://github.com/ChainSafe/lodestar/issues/6194
const hashTreeRootTimer = this.metrics?.stateHashTreeRootTime.startTimer({
source: isEpochTransition ? StateHashTreeRootSource.prepareNextEpoch : StateHashTreeRootSource.prepareNextSlot,
});
state.hashTreeRoot();
hashTreeRootTimer?.();
}
}
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