fix: fall back to era files for block retrieval on pruned nodes

core/rawdb/chain_freezer.go

@@ -422,3 +422,7 @@ func (f *chainFreezer) TruncateTail(items uint64) (uint64, error) {
 func (f *chainFreezer) SyncAncient() error {
 	return f.ancients.SyncAncient()
 }
+
+func (f *chainFreezer) EraStore() *eradb.Store {
+	return f.eradb
+}

core/rawdb/database.go

@@ -32,6 +32,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb/eradb"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/ethdb/memorydb"
@@ -86,6 +87,27 @@ func (frdb *freezerdb) Freeze() error {
 	return nil
 }
 
+// Unwrapper allows retrieving the underlying database from a wrapper.
+type Unwrapper interface {
+	Unwrap() ethdb.Database
+}
+
+// EraStore returns the eradb.Store from the database if available.
+// Returns nil if the database does not have an era store (e.g. in-memory or no freezer).
+func EraStore(db ethdb.Database) *eradb.Store {
+	for {
+		if frdb, ok := db.(*freezerdb); ok {
+			return frdb.EraStore()
+		}
+		if unwrapper, ok := db.(Unwrapper); ok {
+			db = unwrapper.Unwrap()
+		} else {
+			break
+		}
+	}
+	return nil
+}
+
 // nofreezedb is a database wrapper that disables freezer data retrievals.
 type nofreezedb struct {
 	ethdb.KeyValueStore

core/rawdb/eradb/eradb.go

@@ -26,6 +26,7 @@ import (
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common/lru"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/internal/era"
 	"github.com/ethereum/go-ethereum/internal/era/execdb"
 	"github.com/ethereum/go-ethereum/internal/era/onedb"
@@ -102,6 +103,21 @@ func (db *Store) Close() {
 	}
 }
 
+// GetBlockByNumber returns the block for a given block number.
+func (db *Store) GetBlockByNumber(number uint64) (*types.Block, error) {
+	epoch := number / uint64(era.MaxSize)
+	entry := db.getEraByEpoch(epoch)
+	if entry.err != nil {
+		if errors.Is(entry.err, fs.ErrNotExist) {
+			return nil, nil
+		}
+		return nil, entry.err
+	}
+	defer db.doneWithFile(epoch, entry)
+
+	return entry.file.GetBlockByNumber(number)
+}
+
 // GetRawBody returns the raw body for a given block number.
 func (db *Store) GetRawBody(number uint64) ([]byte, error) {
 	epoch := number / uint64(era.MaxSize)

eth/api_backend.go

@@ -156,10 +156,19 @@ func (b *EthAPIBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumbe
 		bn = b.HistoryPruningCutoff()
 	}
 	block := b.eth.blockchain.GetBlockByNumber(bn)
-	if block == nil && bn < b.HistoryPruningCutoff() {
+	if block != nil {
+		return block, nil
+	}
+	// Block not found in the local database, try the ERA store as a fallback.
+	if eraStore := rawdb.EraStore(b.eth.chainDb); eraStore != nil {
+		if eraBlock, err := eraStore.GetBlockByNumber(bn); err == nil && eraBlock != nil {
+			return eraBlock, nil
+		}
+	}
+	if bn < b.HistoryPruningCutoff() {
 		return nil, &history.PrunedHistoryError{}
 	}
-	return block, nil
+	return nil, nil
 }
 
 func (b *EthAPIBackend) BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {

node/node.go

@@ -777,6 +777,11 @@ func (db *closeTrackingDB) Close() error {
 	return db.Database.Close()
 }
 
+// Unwrap returns the underlying database.
+func (db *closeTrackingDB) Unwrap() ethdb.Database {
+	return db.Database
+}
+
 // wrapDatabase ensures the database will be auto-closed when Node is closed.
 func (n *Node) wrapDatabase(db ethdb.Database) ethdb.Database {
 	wrapper := &closeTrackingDB{db, n}