caching epoch seed in context so that getNextEpochBeaconProposer can …

…be independent of state

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,
@@ -20,6 +21,7 @@ import {
   isAggregatorFromCommitteeLength,
   computeProposers,
   computeSyncPeriodAtEpoch,
+  getSeed,
 } from "../util";
 import {computeEpochShuffling, IEpochShuffling} from "../util/epochShuffling";
 import {EffectiveBalanceIncrements, getEffectiveBalanceIncrementsWithLen} from "./effectiveBalanceIncrements";
@@ -161,6 +163,8 @@ export class EpochContext {
   epoch: Epoch;
   syncPeriod: SyncPeriod;
 
+  beaconProposerEpochSeed: Uint8Array;
+
   constructor(data: {
     config: IBeaconConfig;
     pubkey2index: PubkeyIndexMap;
@@ -181,6 +185,7 @@ export class EpochContext {
     nextSyncCommitteeIndexed: SyncCommitteeCache;
     epoch: Epoch;
     syncPeriod: SyncPeriod;
+    beaconProposerEpochSeed: Uint8Array;
   }) {
     this.config = data.config;
     this.pubkey2index = data.pubkey2index;
@@ -201,6 +206,7 @@ export class EpochContext {
     this.nextSyncCommitteeIndexed = data.nextSyncCommitteeIndexed;
     this.epoch = data.epoch;
     this.syncPeriod = data.syncPeriod;
+    this.beaconProposerEpochSeed = data.beaconProposerEpochSeed;
   }
 
   /**
@@ -280,9 +286,13 @@ export class EpochContext {
       : computeEpochShuffling(state, previousActiveIndices, previousEpoch);
     const nextShuffling = computeEpochShuffling(state, nextActiveIndices, nextEpoch);
 
+    const beaconProposerEpochSeed = getSeed(state, currentShuffling.epoch, 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(beaconProposerEpochSeed, currentShuffling, effectiveBalanceIncrements)
+        : [];
 
     // Only after altair, compute the indices of the current sync committee
     const afterAltairFork = currentEpoch >= config.ALTAIR_FORK_EPOCH;
@@ -345,6 +355,7 @@ export class EpochContext {
       nextSyncCommitteeIndexed,
       epoch: currentEpoch,
       syncPeriod: computeSyncPeriodAtEpoch(currentEpoch),
+      beaconProposerEpochSeed: beaconProposerEpochSeed,
     });
   }
 
@@ -380,6 +391,7 @@ export class EpochContext {
       nextSyncCommitteeIndexed: this.nextSyncCommitteeIndexed,
       epoch: this.epoch,
       syncPeriod: this.syncPeriod,
+      beaconProposerEpochSeed: this.beaconProposerEpochSeed,
     });
   }
 
@@ -400,7 +412,11 @@ export class EpochContext {
     const nextEpoch = currEpoch + 1;
 
     this.nextShuffling = computeEpochShuffling(state, epochProcess.nextEpochShufflingActiveValidatorIndices, nextEpoch);
-    this.proposers = computeProposers(state, this.currentShuffling, this.effectiveBalanceIncrements);
+    this.proposers = computeProposers(
+      this.beaconProposerEpochSeed,
+      this.currentShuffling,
+      this.effectiveBalanceIncrements
+    );
 
     // TODO: DEDUPLICATE from createEpochContext
     //
@@ -478,11 +494,11 @@ export class EpochContext {
     return (committeesSinceEpochStart + committeeIndex) % ATTESTATION_SUBNET_COUNT;
   }
 
-  getNextEpochBeaconProposer(state: BeaconStateAllForks): ValidatorIndex[] {
+  getNextEpochBeaconProposer(): ValidatorIndex[] {
     const nextShuffling = this.nextShuffling;
     let nextProposers = this.nextEpochProposers.get(nextShuffling.epoch);
     if (!nextProposers) {
-      nextProposers = computeProposers(state, nextShuffling, this.effectiveBalanceIncrements);
+      nextProposers = computeProposers(this.beaconProposerEpochSeed, nextShuffling, this.effectiveBalanceIncrements);
       // Only keep proposers for one epoch in the future, so clear before setting new value
       this.nextEpochProposers.clear();
       this.nextEpochProposers.set(nextShuffling.epoch, nextProposers);

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++) {

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,
 } from "../../../../src";
+import {computeProposers} from "../../../../src";
+import {getSeed} from "../../../../lib";
 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);
     },
   });
 

packages/lodestar/src/api/impl/validator/index.ts

@@ -285,7 +285,7 @@ export function getValidatorApi({chain, config, logger, metrics, network, sync}:
       // Note: There is a small probability that returned validators differs
       // than what is returned when the epoch is reached.
       if (epoch === nextEpoch) {
-        indexes.push(...state.epochCtx.getNextEpochBeaconProposer(state));
+        indexes.push(...state.epochCtx.getNextEpochBeaconProposer());
       } else {
         // Gather indexes to get pubkeys in batch (performance optimization)
         for (let i = 0; i < SLOTS_PER_EPOCH; i++) {