diff --git a/packages/beacon-state-transition/src/cache/epochContext.ts b/packages/beacon-state-transition/src/cache/epochContext.ts index d5428cd90df..a6fe840764e 100644 --- a/packages/beacon-state-transition/src/cache/epochContext.ts +++ b/packages/beacon-state-transition/src/cache/epochContext.ts @@ -3,6 +3,7 @@ import {BLSSignature, CommitteeIndex, Epoch, Slot, ValidatorIndex, phase0, SyncP import {createIBeaconConfig, IBeaconConfig, IChainConfig} from "@chainsafe/lodestar-config"; import { ATTESTATION_SUBNET_COUNT, + DOMAIN_BEACON_PROPOSER, EFFECTIVE_BALANCE_INCREMENT, FAR_FUTURE_EPOCH, GENESIS_EPOCH, @@ -18,8 +19,9 @@ import { getChurnLimit, isActiveValidator, isAggregatorFromCommitteeLength, - computeProposers, computeSyncPeriodAtEpoch, + getSeed, + computeProposers, } from "../util"; import {computeEpochShuffling, IEpochShuffling} from "../util/epochShuffling"; import {EffectiveBalanceIncrements, getEffectiveBalanceIncrementsWithLen} from "./effectiveBalanceIncrements"; @@ -47,6 +49,9 @@ export type EpochContextOpts = { skipSyncPubkeys?: boolean; }; +/** Defers computing proposers by persisting only the seed, and dropping it once indexes are computed */ +type ProposersDeferred = {computed: false; seed: Uint8Array} | {computed: true; indexes: ValidatorIndex[]}; + /** * EpochContext is the parent object of: * - Any data-structures not part of the spec'ed BeaconState @@ -95,6 +100,14 @@ export class EpochContext { * 32 x Number */ proposers: ValidatorIndex[]; + + /** + * The next proposer seed is only used in the getBeaconProposersNextEpoch call. It cannot be moved into + * getBeaconProposersNextEpoch because it needs state as input and all data needed by getBeaconProposersNextEpoch + * should be in the epoch context. + */ + proposersNextEpoch: ProposersDeferred; + /** * Shuffling of validator indexes. Immutable through the epoch, then it's replaced entirely. * Note: Per spec definition, shuffling will always be defined. They are never called before loadState() @@ -155,6 +168,7 @@ export class EpochContext { pubkey2index: PubkeyIndexMap; index2pubkey: Index2PubkeyCache; proposers: number[]; + proposersNextEpoch: ProposersDeferred; previousShuffling: IEpochShuffling; currentShuffling: IEpochShuffling; nextShuffling: IEpochShuffling; @@ -175,6 +189,7 @@ export class EpochContext { this.pubkey2index = data.pubkey2index; this.index2pubkey = data.index2pubkey; this.proposers = data.proposers; + this.proposersNextEpoch = data.proposersNextEpoch; this.previousShuffling = data.previousShuffling; this.currentShuffling = data.currentShuffling; this.nextShuffling = data.nextShuffling; @@ -269,9 +284,18 @@ export class EpochContext { : computeEpochShuffling(state, previousActiveIndices, previousEpoch); const nextShuffling = computeEpochShuffling(state, nextActiveIndices, nextEpoch); + const currentProposerSeed = getSeed(state, currentEpoch, DOMAIN_BEACON_PROPOSER); + // Allow to create CachedBeaconState for empty states const proposers = - state.validators.length > 0 ? computeProposers(state, currentShuffling, effectiveBalanceIncrements) : []; + state.validators.length > 0 + ? computeProposers(currentProposerSeed, currentShuffling, effectiveBalanceIncrements) + : []; + + const proposersNextEpoch: ProposersDeferred = { + computed: false, + seed: getSeed(state, nextEpoch, DOMAIN_BEACON_PROPOSER), + }; // Only after altair, compute the indices of the current sync committee const afterAltairFork = currentEpoch >= config.ALTAIR_FORK_EPOCH; @@ -319,6 +343,7 @@ export class EpochContext { pubkey2index, index2pubkey, proposers, + proposersNextEpoch, previousShuffling, currentShuffling, nextShuffling, @@ -351,6 +376,7 @@ export class EpochContext { index2pubkey: this.index2pubkey, // Immutable data proposers: this.proposers, + proposersNextEpoch: this.proposersNextEpoch, previousShuffling: this.previousShuffling, currentShuffling: this.currentShuffling, nextShuffling: this.nextShuffling, @@ -389,7 +415,11 @@ export class EpochContext { const nextEpoch = currEpoch + 1; this.nextShuffling = computeEpochShuffling(state, epochProcess.nextEpochShufflingActiveValidatorIndices, nextEpoch); - this.proposers = computeProposers(state, this.currentShuffling, this.effectiveBalanceIncrements); + const currentProposerSeed = getSeed(state, this.currentShuffling.epoch, DOMAIN_BEACON_PROPOSER); + this.proposers = computeProposers(currentProposerSeed, this.currentShuffling, this.effectiveBalanceIncrements); + + // Only pre-compute the seed since it's very cheap. Do the expensive computeProposers() call only on demand. + this.proposersNextEpoch = {computed: false, seed: getSeed(state, this.nextShuffling.epoch, DOMAIN_BEACON_PROPOSER)}; // TODO: DEDUPLICATE from createEpochContext // @@ -477,6 +507,60 @@ export class EpochContext { return this.proposers[slot % SLOTS_PER_EPOCH]; } + getBeaconProposers(): ValidatorIndex[] { + return this.proposers; + } + + /** + * We allow requesting proposal duties 1 epoch in the future as in normal network conditions it's possible to predict + * the correct shuffling with high probability. While knowing the proposers in advance is not useful for consensus, + * users want to know it to plan manteinance and avoid missing block proposals. + * + * **How to predict future proposers** + * + * Proposer duties for epoch N are guaranteed to be known at epoch N. Proposer duties depend exclusively on: + * 1. seed (from randao_mix): known 2 epochs ahead + * 2. active validator set: known 4 epochs ahead + * 3. effective balance: not known ahead + * + * ```python + * def get_beacon_proposer_index(state: BeaconState) -> ValidatorIndex: + * epoch = get_current_epoch(state) + * seed = hash(get_seed(state, epoch, DOMAIN_BEACON_PROPOSER) + uint_to_bytes(state.slot)) + * indices = get_active_validator_indices(state, epoch) + * return compute_proposer_index(state, indices, seed) + * ``` + * + * **1**: If `MIN_SEED_LOOKAHEAD = 1` the randao_mix used for the seed is from 2 epochs ago. So at epoch N, the seed + * is known and unchangable for duties at epoch N+1 and N+2 for proposer duties. + * + * ```python + * def get_seed(state: BeaconState, epoch: Epoch, domain_type: DomainType) -> Bytes32: + * mix = get_randao_mix(state, Epoch(epoch - MIN_SEED_LOOKAHEAD - 1)) + * return hash(domain_type + uint_to_bytes(epoch) + mix) + * ``` + * + * **2**: The active validator set can be predicted `MAX_SEED_LOOKAHEAD` in advance due to how activations are + * processed. We already compute the active validator set for the next epoch to optimize epoch processing, so it's + * reused here. + * + * **3**: Effective balance is not known ahead of time, but it rarely changes. Even if it changes, only a few + * balances are sampled to adjust the probability of the next selection (32 per epoch on average). So to invalidate + * the prediction the effective of one of those 32 samples should change and change the random_byte inequality. + */ + getBeaconProposersNextEpoch(): ValidatorIndex[] { + if (!this.proposersNextEpoch.computed) { + const indexes = computeProposers( + this.proposersNextEpoch.seed, + this.nextShuffling, + this.effectiveBalanceIncrements + ); + this.proposersNextEpoch = {computed: true, indexes}; + } + + return this.proposersNextEpoch.indexes; + } + /** * Return the indexed attestation corresponding to ``attestation``. */ diff --git a/packages/beacon-state-transition/src/index.ts b/packages/beacon-state-transition/src/index.ts index 325d5298ace..6b7b8446731 100644 --- a/packages/beacon-state-transition/src/index.ts +++ b/packages/beacon-state-transition/src/index.ts @@ -30,4 +30,9 @@ export {EpochProcess, beforeProcessEpoch} from "./cache/epochProcess"; // Aux data-structures export {PubkeyIndexMap, Index2PubkeyCache} from "./cache/pubkeyCache"; -export {EffectiveBalanceIncrements, getEffectiveBalanceIncrementsZeroed} from "./cache/effectiveBalanceIncrements"; + +export { + EffectiveBalanceIncrements, + getEffectiveBalanceIncrementsZeroed, + getEffectiveBalanceIncrementsWithLen, +} from "./cache/effectiveBalanceIncrements"; diff --git a/packages/beacon-state-transition/src/util/seed.ts b/packages/beacon-state-transition/src/util/seed.ts index 86f30bc293a..1e544943845 100644 --- a/packages/beacon-state-transition/src/util/seed.ts +++ b/packages/beacon-state-transition/src/util/seed.ts @@ -6,7 +6,6 @@ import {digest} from "@chainsafe/as-sha256"; import {Epoch, Bytes32, DomainType, ValidatorIndex} from "@chainsafe/lodestar-types"; import {assert, bytesToBigInt, intToBytes} from "@chainsafe/lodestar-utils"; import { - DOMAIN_BEACON_PROPOSER, DOMAIN_SYNC_COMMITTEE, EFFECTIVE_BALANCE_INCREMENT, EPOCHS_PER_HISTORICAL_VECTOR, @@ -25,11 +24,10 @@ import {computeEpochAtSlot} from "./epoch"; * Compute proposer indices for an epoch */ export function computeProposers( - state: BeaconStateAllForks, + epochSeed: Uint8Array, shuffling: {epoch: Epoch; activeIndices: ValidatorIndex[]}, effectiveBalanceIncrements: EffectiveBalanceIncrements ): number[] { - const epochSeed = getSeed(state, shuffling.epoch, DOMAIN_BEACON_PROPOSER); const startSlot = computeStartSlotAtEpoch(shuffling.epoch); const proposers = []; for (let slot = startSlot; slot < startSlot + SLOTS_PER_EPOCH; slot++) { diff --git a/packages/beacon-state-transition/test/perf/allForks/util/shufflings.test.ts b/packages/beacon-state-transition/test/perf/allForks/util/shufflings.test.ts index e0ba1ebdb1e..fbc52a78971 100644 --- a/packages/beacon-state-transition/test/perf/allForks/util/shufflings.test.ts +++ b/packages/beacon-state-transition/test/perf/allForks/util/shufflings.test.ts @@ -1,13 +1,15 @@ import {itBench} from "@dapplion/benchmark"; import {Epoch} from "@chainsafe/lodestar-types"; +import {DOMAIN_BEACON_PROPOSER} from "@chainsafe/lodestar-params"; import { computeEpochAtSlot, CachedBeaconStateAllForks, computeEpochShuffling, getNextSyncCommittee, + computeProposers, + getSeed, } from "../../../../src"; import {generatePerfTestCachedStatePhase0, numValidators} from "../../util"; -import {computeProposers} from "../../../../src/util/seed"; describe("epoch shufflings", () => { let state: CachedBeaconStateAllForks; @@ -25,7 +27,8 @@ describe("epoch shufflings", () => { itBench({ id: `computeProposers - vc ${numValidators}`, fn: () => { - computeProposers(state, state.epochCtx.nextShuffling, state.epochCtx.effectiveBalanceIncrements); + const epochSeed = getSeed(state, state.epochCtx.nextShuffling.epoch, DOMAIN_BEACON_PROPOSER); + computeProposers(epochSeed, state.epochCtx.nextShuffling, state.epochCtx.effectiveBalanceIncrements); }, }); diff --git a/packages/lodestar/src/api/impl/validator/index.ts b/packages/lodestar/src/api/impl/validator/index.ts index 5d065ebb1f1..06b7b1d7272 100644 --- a/packages/lodestar/src/api/impl/validator/index.ts +++ b/packages/lodestar/src/api/impl/validator/index.ts @@ -278,14 +278,17 @@ export function getValidatorApi({chain, config, logger, metrics, network, sync}: const state = await chain.getHeadStateAtCurrentEpoch(); - const duties: routes.validator.ProposerDuty[] = []; - const indexes: ValidatorIndex[] = []; - - // Gather indexes to get pubkeys in batch (performance optimization) - for (let i = 0; i < SLOTS_PER_EPOCH; i++) { - // getBeaconProposer ensures the requested epoch is correct - const validatorIndex = state.epochCtx.getBeaconProposer(startSlot + i); - indexes.push(validatorIndex); + const stateEpoch = state.epochCtx.epoch; + let indexes: ValidatorIndex[] = []; + + if (epoch === stateEpoch) { + indexes = state.epochCtx.getBeaconProposers(); + } else if (epoch === stateEpoch + 1) { + // Requesting duties for next epoch is allow since they can be predicted with high probabilities. + // @see `epochCtx.getBeaconProposersNextEpoch` JSDocs for rationale. + indexes = state.epochCtx.getBeaconProposersNextEpoch(); + } else { + throw Error(`Proposer duties for epoch ${epoch} not supported, current epoch ${stateEpoch}`); } // NOTE: this is the fastest way of getting compressed pubkeys. @@ -294,6 +297,7 @@ export function getValidatorApi({chain, config, logger, metrics, network, sync}: // TODO: Add a flag to just send 0x00 as pubkeys since the Lodestar validator does not need them. const pubkeys = getPubkeysForIndices(state.validators, indexes); + const duties: routes.validator.ProposerDuty[] = []; for (let i = 0; i < SLOTS_PER_EPOCH; i++) { duties.push({slot: startSlot + i, validatorIndex: indexes[i], pubkey: pubkeys[i]}); } diff --git a/packages/lodestar/test/unit/api/impl/validator/duties/proposer.test.ts b/packages/lodestar/test/unit/api/impl/validator/duties/proposer.test.ts index 46efb30924a..65847110c92 100644 --- a/packages/lodestar/test/unit/api/impl/validator/duties/proposer.test.ts +++ b/packages/lodestar/test/unit/api/impl/validator/duties/proposer.test.ts @@ -52,7 +52,64 @@ describe("get proposers api impl", function () { api = getValidatorApi(modules); }); - it("should get proposers", async function () { + it("should get proposers for next epoch", async function () { + syncStub.isSynced.returns(true); + server.sandbox.stub(chainStub.clock, "currentEpoch").get(() => 0); + server.sandbox.stub(chainStub.clock, "currentSlot").get(() => 0); + dbStub.block.get.resolves({message: {stateRoot: Buffer.alloc(32)}} as any); + const state = generateState( + { + slot: 0, + validators: generateValidators(25, { + effectiveBalance: MAX_EFFECTIVE_BALANCE, + activationEpoch: 0, + exitEpoch: FAR_FUTURE_EPOCH, + }), + balances: Array.from({length: 25}, () => MAX_EFFECTIVE_BALANCE), + }, + config + ); + + const cachedState = createCachedBeaconStateTest(state, config); + chainStub.getHeadStateAtCurrentEpoch.resolves(cachedState); + const stubGetNextBeaconProposer = sinon.stub(cachedState.epochCtx, "getBeaconProposersNextEpoch"); + const stubGetBeaconProposer = sinon.stub(cachedState.epochCtx, "getBeaconProposer"); + stubGetNextBeaconProposer.returns([1]); + // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-call,@typescript-eslint/no-unsafe-member-access + const {data: result} = await api.getProposerDuties(1); + // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access + expect(result.length).to.be.equal(SLOTS_PER_EPOCH, "result should be equals to slots per epoch"); + expect(stubGetNextBeaconProposer.called, "stubGetBeaconProposer function should not have been called").to.be.true; + expect(stubGetBeaconProposer.called, "stubGetBeaconProposer function should have been called").to.be.false; + }); + + it("should have different proposer for current and next epoch", async function () { + syncStub.isSynced.returns(true); + server.sandbox.stub(chainStub.clock, "currentEpoch").get(() => 0); + server.sandbox.stub(chainStub.clock, "currentSlot").get(() => 0); + dbStub.block.get.resolves({message: {stateRoot: Buffer.alloc(32)}} as any); + const state = generateState( + { + slot: 0, + validators: generateValidators(25, { + effectiveBalance: MAX_EFFECTIVE_BALANCE, + activationEpoch: 0, + exitEpoch: FAR_FUTURE_EPOCH, + }), + balances: Array.from({length: 25}, () => MAX_EFFECTIVE_BALANCE), + }, + config + ); + const cachedState = createCachedBeaconStateTest(state, config); + chainStub.getHeadStateAtCurrentEpoch.resolves(cachedState); + const stubGetBeaconProposer = sinon.stub(cachedState.epochCtx, "getBeaconProposer"); + stubGetBeaconProposer.returns(1); + const {data: currentProposers} = await api.getProposerDuties(0); + const {data: nextProposers} = await api.getProposerDuties(1); + expect(currentProposers).to.not.deep.equal(nextProposers, "current proposer and next proposer should be different"); + }); + + it("should not get proposers for more than one epoch in the future", async function () { syncStub.isSynced.returns(true); server.sandbox.stub(chainStub.clock, "currentEpoch").get(() => 0); server.sandbox.stub(chainStub.clock, "currentSlot").get(() => 0); @@ -71,8 +128,8 @@ describe("get proposers api impl", function () { ); const cachedState = createCachedBeaconStateTest(state, config); chainStub.getHeadStateAtCurrentEpoch.resolves(cachedState); - sinon.stub(cachedState.epochCtx, "getBeaconProposer").returns(1); - const {data: result} = await api.getProposerDuties(0); - expect(result.length).to.be.equal(SLOTS_PER_EPOCH); + const stubGetBeaconProposer = sinon.stub(cachedState.epochCtx, "getBeaconProposer"); + stubGetBeaconProposer.throws(); + expect(api.getProposerDuties(2), "calling getProposerDuties should throw").to.eventually.throws; }); });