feat: fall back to EC finalized tipset if F3 is too far behind in eth APIs

CHANGELOG.md

@@ -14,7 +14,7 @@
 - fix(eth): always return nil for eth transactions not found ([filecoin-project/lotus#12999](https://github.com/filecoin-project/lotus/pull/12999))
 - feat: add gas to application metric reporting `vm/applyblocks_early_gas`, `vm/applyblocks_messages_gas`, `vm/applyblocks_cron_gas` ([filecoin-project/lotus#13030](https://github.com/filecoin-project/lotus/pull/13030))
 - feat: fall back to EC if F3 finalized tipeset is older than 900 epochs ([filecoin-project/lotus#13066](https://github.com/filecoin-project/lotus/pull/13066))
-
+- feat: fall back to EC finalized tipset if F3 is too far behind in eth APIs ([filecoin-project/lotus#13070](https://github.com/filecoin-project/lotus/pull/13070))
 
 ### Experimental v2 APIs with F3 awareness
 

itests/eth_api_f3_test.go

@@ -330,6 +330,18 @@ func TestEthAPIWithF3(t *testing.T) {
 			wantTipSetV1: ecSafeV1,
 			wantErrV2:    internalF3Error.Error(),
 		},
+		{
+			name:     "finalize tag when f3 is too far behind falls back to ec",
+			blkParam: "finalized",
+			setup: func(t *testing.T) {
+				mockF3.Running = true
+				mockF3.Finalizing = true
+				mockF3.LatestCert = plausibleCertAt(t, targetHeight-policy.ChainFinality-5)
+				mockF3.LatestCertErr = nil
+			},
+			wantTipSetV1: ecFinalized,
+			wantTipSetV2: ecFinalized,
+		},
 		{
 			name:     "latest tag when f3 fails is ok",
 			blkParam: "latest",

node/impl/eth/tipsetresolver.go

@@ -91,6 +91,18 @@ func (tsr *tipSetResolver) getFinalizedF3TipSet(ctx context.Context) (*types.Tip
 		// F3 is disabled or not ready; fall back to EC finality.
 		return tsr.getFinalizedECTipSet(ctx)
 	}
+	// Check F3 finalized tipset against the heaviest tipset, and if it is too far
+	// behind fall back to EC.
+	head := tsr.cs.GetHeaviestTipSet()
+	if head == nil {
+		return nil, xerrors.Errorf("no known heaviest tipset")
+	}
+	f3FinalizedHeight := abi.ChainEpoch(cert.ECChain.Head().Epoch)
+	if head.Height()-f3FinalizedHeight > policy.ChainFinality {
+		log.Debugw("Falling back to EC finalized tipset as the latest F3 finalized tipset is too far behind", "headHeight", head.Height(), "f3FinalizedHeight", f3FinalizedHeight)
+		return tsr.getFinalizedECTipSet(ctx)
+	}
+	// F3 is finalizing a higher height than EC safe; return F3 tipset
 	return tsr.getFinalizedF3TipSetFromCert(ctx, cert)
 }