feat(sae): Store last accepted hash (#5544)

Author: alarso16

graft/coreth/core/blockchain.go

@@ -843,7 +843,7 @@ func (bc *BlockChain) writeHeadBlock(block *types.Block) {
 	// Add the block to the canonical chain number scheme and mark as the head
 	batch := bc.db.NewBatch()
 	rawdb.WriteCanonicalHash(batch, block.Hash(), block.NumberU64())
-
+	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
 
@@ -2192,6 +2192,7 @@ func (bc *BlockChain) ResetToStateSyncedBlock(block *types.Block) error {
 	}
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
+	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
 	customrawdb.WriteSnapshotBlockHash(batch, block.Hash())
 	rawdb.WriteSnapshotRoot(batch, block.Root())
 	if err := customrawdb.WriteSyncPerformed(batch, block.NumberU64()); err != nil {

graft/coreth/core/genesis.go

@@ -399,6 +399,7 @@ func (g *Genesis) Commit(db ethdb.Database, triedb *triedb.Database) (*types.Blo
 	rawdb.WriteCanonicalHash(batch, block.Hash(), block.NumberU64())
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
+	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
 	rawdb.WriteFinalizedBlockHash(batch, block.Hash())
 	rawdb.WriteChainConfig(batch, block.Hash(), config)
 	if err := batch.Write(); err != nil {

graft/subnet-evm/core/blockchain.go

@@ -860,7 +860,7 @@ func (bc *BlockChain) writeHeadBlock(block *types.Block) {
 	// Add the block to the canonical chain number scheme and mark as the head
 	batch := bc.db.NewBatch()
 	rawdb.WriteCanonicalHash(batch, block.Hash(), block.NumberU64())
-
+	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
 
@@ -2231,6 +2231,7 @@ func (bc *BlockChain) ResetToStateSyncedBlock(block *types.Block) error {
 	}
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
+	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
 	customrawdb.WriteSnapshotBlockHash(batch, block.Hash())
 	rawdb.WriteSnapshotRoot(batch, block.Root())
 	if err := customrawdb.WriteSyncPerformed(batch, block.NumberU64()); err != nil {

graft/subnet-evm/core/genesis.go

@@ -428,6 +428,7 @@ func (g *Genesis) Commit(db ethdb.Database, triedb *triedb.Database) (*types.Blo
 	rawdb.WriteCanonicalHash(batch, block.Hash(), block.NumberU64())
 	rawdb.WriteHeadBlockHash(batch, block.Hash())
 	rawdb.WriteHeadHeaderHash(batch, block.Hash())
+	rawdb.WriteHeadFastBlockHash(batch, block.Hash())
 	rawdb.WriteFinalizedBlockHash(batch, block.Hash())
 	customrawdb.WriteChainConfig(batch, block.Hash(), config, params.GetExtra(config).UpgradeConfig)
 	if err := batch.Write(); err != nil {

vms/saevm/cchain/genesis.go

@@ -240,6 +240,7 @@ func writeGenesisBlock(db ethdb.Database, block *types.Block, config *ethparams.
 	rawdb.WriteFinalizedBlockHash(b, hash)
 	rawdb.WriteHeadBlockHash(b, hash)
 	rawdb.WriteHeadHeaderHash(b, hash)
+	rawdb.WriteHeadFastBlockHash(b, hash)
 	rawdb.WriteChainConfig(b, hash, config)
 	return b.Write()
 }

vms/saevm/docs/invariants.md

@@ -31,15 +31,15 @@ While it also has a notion of a "safe" block (with reduced probability of re-org
 
 #### Mapping
 
-| SAE      | `rawdb`   |
-| -------- | --------- |
-| Accepted | Canonical |
-| Executed | Head      |
-| Settled  | Finalized |
+| SAE      | `rawdb`             |
+| -------- | ------------------- |
+| Accepted | Canonical, HeadFast |
+| Executed | Head                |
+| Settled  | Finalized           |
 
 #### Rationale
 
-* Accepted and canonical are effectively identical concepts, save for nuanced differences between the consensus mechanisms.
+* Accepted and canonical are effectively identical concepts, save for nuanced differences between the consensus mechanisms. `libevm`'s `HeadFast` denotes a recorded block whose state has not yet been executed; this aligns with SAE's definition of Accepted and is convenient for indexing the last-accepted block.
 
 * From an API perspective, we treat "latest" (i.e. the chain head) as the last-executed block.
 Mirroring this on disk allows for simple integration with the upstream API implementations.

vms/saevm/sae/consensus.go

@@ -59,6 +59,7 @@ func (vm *VM) AcceptBlock(ctx context.Context, b *blocks.Block) error {
 		rawdb.WriteTxLookupEntriesByBlock(batch, b.EthBlock())
 		// D(b ∈ A)
 		rawdb.WriteCanonicalHash(batch, b.Hash(), b.NumberU64())
+		rawdb.WriteHeadFastBlockHash(batch, b.Hash())
 
 		if err := batch.Write(); err != nil {
 			return err

vms/saevm/sae/recovery.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"iter"
-	"math"
 	"sync/atomic"
 
 	"github.com/ava-labs/libevm/common"
@@ -96,15 +95,20 @@ func (rec *recovery) lastCommittedBlock() (_ *blocks.Block, retErr error) {
 }
 
 func (rec *recovery) canonicalAfter(parent *blocks.Block) iter.Seq2[*blocks.Block, error] {
-	nums, _ := rawdb.ReadAllCanonicalHashes(rec.db, parent.NumberU64()+1, math.MaxUint64, math.MaxInt)
-
 	return func(yield func(*blocks.Block, error) bool) {
-		for _, num := range nums {
-			b, err := rec.newCanonicalBlock(num, parent)
+		lastAcceptedHash := rawdb.ReadHeadFastBlockHash(rec.db)
+		if lastAcceptedHash == (common.Hash{}) {
+			// SAE writes this hash on [VM.AcceptBlock], so the set of accepted,
+			// asynchronous blocks MUST be empty.
+			return
+		}
+
+		for curr := parent; curr.Hash() != lastAcceptedHash; {
+			b, err := rec.newCanonicalBlock(curr.Height()+1, curr)
 			if !yield(b, err) || err != nil {
 				return
 			}
-			parent = b
+			curr = b
 		}
 	}
 }

vms/saevm/sae/recovery_test.go

@@ -137,6 +137,10 @@ func TestRecoverSimple(t *testing.T) {
 		numBlocks int
 		archival  bool
 	}{
+		{
+			name:      "genesis",
+			numBlocks: 0,
+		},
 		{
 			name:      "archival",
 			numBlocks: 10,