feat: defer voluntary exits with transient validation failures

packages/beacon-node/src/api/impl/beacon/pool/index.ts

@@ -212,7 +212,21 @@ export function getBeaconPoolApi({
     },
 
     async submitPoolVoluntaryExit({signedVoluntaryExit}) {
-      await validateApiVoluntaryExit(chain, signedVoluntaryExit);
+      const result = await validateApiVoluntaryExit(chain, signedVoluntaryExit);
+
+      if (result.status === "deferred") {
+        const currentEpoch = chain.clock.currentEpoch;
+        const inserted = chain.deferredVoluntaryExitPool.insert(signedVoluntaryExit, result.validity, currentEpoch);
+        if (!inserted) {
+          throw new ApiError(400, "Deferred voluntary exit pool is full or already contains this validator");
+        }
+        logger.info("Voluntary exit deferred until transient conditions are met", {
+          validatorIndex: signedVoluntaryExit.message.validatorIndex,
+          reason: result.validity,
+        });
+        return;
+      }
+
       chain.opPool.insertVoluntaryExit(signedVoluntaryExit);
       chain.emitter.emit(routes.events.EventType.voluntaryExit, signedVoluntaryExit);
       await network.publishVoluntaryExit(signedVoluntaryExit);

packages/beacon-node/src/chain/chain.ts

@@ -84,6 +84,7 @@ import {LightClientServer} from "./lightClient/index.js";
 import {
   AggregatedAttestationPool,
   AttestationPool,
+  DeferredVoluntaryExitPool,
   ExecutionPayloadBidPool,
   OpPool,
   PayloadAttestationPool,
@@ -180,6 +181,7 @@ export class BeaconChain implements IBeaconChain {
   readonly executionPayloadBidPool: ExecutionPayloadBidPool;
   readonly payloadAttestationPool: PayloadAttestationPool;
   readonly opPool: OpPool;
+  readonly deferredVoluntaryExitPool: DeferredVoluntaryExitPool;
 
   // Gossip seen cache
   readonly seenAttesters = new SeenAttesters();
@@ -306,6 +308,7 @@ export class BeaconChain implements IBeaconChain {
     this.executionPayloadBidPool = new ExecutionPayloadBidPool();
     this.payloadAttestationPool = new PayloadAttestationPool(config, clock, metrics);
     this.opPool = new OpPool(config);
+    this.deferredVoluntaryExitPool = new DeferredVoluntaryExitPool(logger);
 
     this.seenAggregatedAttestations = new SeenAggregatedAttestations(metrics);
     this.seenContributionAndProof = new SeenContributionAndProof(metrics);
@@ -1406,6 +1409,7 @@ export class BeaconChain implements IBeaconChain {
     // aggregatedAttestationPool tracks metrics on its own
     metrics.opPool.attestationPool.size.set(this.attestationPool.getAttestationCount());
     metrics.opPool.attesterSlashingPoolSize.set(this.opPool.attesterSlashingsSize);
+    metrics.opPool.deferredVoluntaryExitPool.size.set(this.deferredVoluntaryExitPool.size());
     metrics.opPool.proposerSlashingPoolSize.set(this.opPool.proposerSlashingsSize);
     metrics.opPool.voluntaryExitPoolSize.set(this.opPool.voluntaryExitsSize);
     metrics.opPool.syncCommitteeMessagePoolSize.set(this.syncCommitteeMessagePool.size);

packages/beacon-node/src/chain/interface.ts

@@ -44,6 +44,7 @@ import {LightClientServer} from "./lightClient/index.js";
 import {AggregatedAttestationPool} from "./opPools/aggregatedAttestationPool.js";
 import {
   AttestationPool,
+  DeferredVoluntaryExitPool,
   ExecutionPayloadBidPool,
   OpPool,
   PayloadAttestationPool,
@@ -125,6 +126,7 @@ export interface IBeaconChain {
   readonly executionPayloadBidPool: ExecutionPayloadBidPool;
   readonly payloadAttestationPool: PayloadAttestationPool;
   readonly opPool: OpPool;
+  readonly deferredVoluntaryExitPool: DeferredVoluntaryExitPool;
 
   // Gossip seen cache
   readonly seenAttesters: SeenAttesters;

packages/beacon-node/src/chain/opPools/deferredVoluntaryExitPool.ts

@@ -0,0 +1,58 @@
+import {Logger} from "@lodestar/logger";
+import {IBeaconStateView, VoluntaryExitValidity, isTransientExitValidity} from "@lodestar/state-transition";
+import {Epoch, ValidatorIndex} from "@lodestar/types";
+import {SignedVoluntaryExit} from "@lodestar/types/phase0";
+
+type DeferredEntry = {
+  exit: SignedVoluntaryExit;
+  validity: VoluntaryExitValidity;
+  insertedAtEpoch: Epoch;
+};
+
+export class DeferredVoluntaryExitPool {
+  private pool = new Map<ValidatorIndex, DeferredEntry>();
+
+  constructor(
+    private readonly logger: Logger,
+    private readonly maxSize = 1024,
+    private readonly maxDeferEpochs = 256
+  ) {}
+
+  insert(exit: SignedVoluntaryExit, validity: VoluntaryExitValidity, currentEpoch: Epoch): boolean {
+    if (!isTransientExitValidity(validity)) return false;
+    if (this.pool.size === this.maxSize) return false;
+    if (this.pool.has(exit.message.validatorIndex)) return false;
+
+    this.pool.set(exit.message.validatorIndex, {exit, validity, insertedAtEpoch: currentEpoch});
+
+    return true;
+  }
+
+  retrieveProcessableExits(state: IBeaconStateView): SignedVoluntaryExit[] {
+    const epoch = state.epoch;
+    const validExits: SignedVoluntaryExit[] = [];
+    for (const [validatorIndex, entry] of this.pool) {
+      try {
+        if (epoch - entry.insertedAtEpoch > this.maxDeferEpochs) {
+          this.pool.delete(validatorIndex);
+          continue;
+        }
+        const validity = state.getVoluntaryExitValidity(entry.exit, false);
+        if (validity === VoluntaryExitValidity.valid) {
+          validExits.push(entry.exit);
+          this.pool.delete(validatorIndex);
+        } else if (!isTransientExitValidity(validity)) {
+          this.pool.delete(validatorIndex);
+        }
+        // Else if still transient - keep
+      } catch (e) {
+        this.logger.debug("Processing deferred voluntary exit failed", {validatorIndex}, e as Error);
+      }
+    }
+    return validExits;
+  }
+
+  size(): number {
+    return this.pool.size;
+  }
+}

packages/beacon-node/src/chain/opPools/index.ts

@@ -1,5 +1,6 @@
 export {AggregatedAttestationPool} from "./aggregatedAttestationPool.js";
 export {AttestationPool} from "./attestationPool.js";
+export {DeferredVoluntaryExitPool} from "./deferredVoluntaryExitPool.js";
 export {ExecutionPayloadBidPool} from "./executionPayloadBidPool.js";
 export {OpPool} from "./opPool.js";
 export {PayloadAttestationPool} from "./payloadAttestationPool.js";

packages/beacon-node/src/chain/regen/interface.ts

@@ -20,6 +20,8 @@ export enum RegenCaller {
   validateGossipAggregateAndProof = "validateGossipAggregateAndProof",
   validateGossipAttestation = "validateGossipAttestation",
   validateGossipVoluntaryExit = "validateGossipVoluntaryExit",
+  validateApiVoluntaryExit = "validateApiVoluntaryExit",
+  publishDeferredVoluntaryExits = "publishDeferredVoluntaryExits",
   validateGossipExecutionPayloadBid = "validateGossipExecutionPayloadBid",
   validateGossipProposerPreferences = "validateGossipProposerPreferences",
   onForkChoiceFinalized = "onForkChoiceFinalized",

packages/beacon-node/src/chain/validation/voluntaryExit.ts

@@ -1,4 +1,4 @@
-import {VoluntaryExitValidity, getVoluntaryExitSignatureSet} from "@lodestar/state-transition";
+import {VoluntaryExitValidity, getVoluntaryExitSignatureSet, isTransientExitValidity} from "@lodestar/state-transition";
 import {phase0} from "@lodestar/types";
 import {
   GossipAction,
@@ -9,12 +9,50 @@ import {
 import {IBeaconChain} from "../index.js";
 import {RegenCaller} from "../regen/index.js";
 
+export type ApiVoluntaryExitResult = {status: "published"} | {status: "deferred"; validity: VoluntaryExitValidity};
+
+// Comments for each call are present inside `validateVoluntaryExit`.
 export async function validateApiVoluntaryExit(
   chain: IBeaconChain,
   voluntaryExit: phase0.SignedVoluntaryExit
-): Promise<void> {
+): Promise<ApiVoluntaryExitResult> {
   const prioritizeBls = true;
-  return validateVoluntaryExit(chain, voluntaryExit, prioritizeBls);
+
+  if (chain.opPool.hasSeenVoluntaryExit(voluntaryExit.message.validatorIndex)) {
+    throw new VoluntaryExitError(GossipAction.IGNORE, {
+      code: VoluntaryExitErrorCode.ALREADY_EXISTS,
+    });
+  }
+
+  const state = await chain.getHeadStateAtCurrentEpoch(RegenCaller.validateApiVoluntaryExit);
+
+  if (voluntaryExit.message.validatorIndex >= state.validatorCount) {
+    throw new VoluntaryExitError(GossipAction.REJECT, {
+      code: VoluntaryExitErrorCode.INACTIVE,
+    });
+  }
+
+  const validity = state.getVoluntaryExitValidity(voluntaryExit, false);
+
+  if (validity !== VoluntaryExitValidity.valid && !isTransientExitValidity(validity)) {
+    throw new VoluntaryExitError(GossipAction.REJECT, {
+      code: voluntaryExitValidityToErrorCode(validity),
+    });
+  }
+
+  const signatureSet = getVoluntaryExitSignatureSet(chain.config, state, voluntaryExit);
+  if (!(await chain.bls.verifySignatureSets([signatureSet], {batchable: true, priority: prioritizeBls}))) {
+    throw new VoluntaryExitError(GossipAction.REJECT, {
+      code: VoluntaryExitErrorCode.INVALID_SIGNATURE,
+    });
+  }
+
+  if (validity !== VoluntaryExitValidity.valid) {
+    // Transient failure — signature is good, defer
+    return {status: "deferred", validity};
+  }
+
+  return {status: "published"};
 }
 
 export async function validateGossipVoluntaryExit(

packages/beacon-node/src/metrics/metrics/lodestar.ts

@@ -1157,6 +1157,12 @@ export function createLodestarMetrics(
         name: "lodestar_oppool_attester_slashing_pool_size",
         help: "Current size of the AttesterSlashingPool",
       }),
+      deferredVoluntaryExitPool: {
+        size: register.gauge({
+          name: "lodestar_oppool_deferred_voluntary_exit_pool_size",
+          help: "Current size of the DeferredVoluntaryExitPool",
+        }),
+      },
       proposerSlashingPoolSize: register.gauge({
         name: "lodestar_oppool_proposer_slashing_pool_size",
         help: "Current size of the ProposerSlashingPool",

packages/beacon-node/src/node/nodejs.ts

@@ -2,6 +2,7 @@ import {setMaxListeners} from "node:events";
 import {PrivateKey} from "@libp2p/interface";
 import {Registry} from "prom-client";
 import {hasher} from "@chainsafe/persistent-merkle-tree";
+import {routes} from "@lodestar/api";
 import {BeaconApiMethods} from "@lodestar/api/beacon/server";
 import {BeaconConfig} from "@lodestar/config";
 import type {LoggerNode} from "@lodestar/logger/node";
@@ -12,6 +13,7 @@ import {sleep, toRootHex} from "@lodestar/utils";
 import {ProcessShutdownCallback} from "@lodestar/validator";
 import {BeaconRestApiServer, getApi} from "../api/index.js";
 import {BeaconChain, IBeaconChain, initBeaconMetrics} from "../chain/index.js";
+import {RegenCaller} from "../chain/regen/index.js";
 import {ValidatorMonitor, createValidatorMonitor} from "../chain/validatorMonitor.js";
 import {IBeaconDb} from "../db/index.js";
 import {initializeExecutionBuilder, initializeExecutionEngine} from "../execution/index.js";
@@ -20,7 +22,7 @@ import {MonitoringService} from "../monitoring/index.js";
 import {Network, getReqRespHandlers} from "../network/index.js";
 import {BackfillSync} from "../sync/backfill/index.js";
 import {BeaconSync, IBeaconSync} from "../sync/index.js";
-import {Clock} from "../util/clock.js";
+import {Clock, ClockEvent} from "../util/clock.js";
 import {runNodeNotifier} from "./notifier.js";
 import {IBeaconNodeOptions} from "./options.js";
 
@@ -334,6 +336,31 @@ export class BeaconNode {
 
     void runNodeNotifier({network, chain, sync, config, logger, signal});
 
+    chain.clock.addListener(ClockEvent.epoch, async () => {
+      try {
+        const state = await chain.getHeadStateAtCurrentEpoch(RegenCaller.publishDeferredVoluntaryExits);
+        const exits = chain.deferredVoluntaryExitPool.retrieveProcessableExits(state);
+        for (const exit of exits) {
+          try {
+            chain.opPool.insertVoluntaryExit(exit);
+            chain.emitter.emit(routes.events.EventType.voluntaryExit, exit);
+            await network.publishVoluntaryExit(exit);
+            logger.info("Voluntary exit successfully published for validator", {
+              validatorIndex: exit.message.validatorIndex,
+            });
+          } catch (e) {
+            logger.warn(
+              "Failed to publish deferred voluntary exit",
+              {validatorIndex: exit.message.validatorIndex},
+              e as Error
+            );
+          }
+        }
+      } catch (e) {
+        logger.warn("Failed to drain deferred voluntary exit pool", {}, e as Error);
+      }
+    });
+
     return new BeaconNode({
       opts,
       config,