core: fix snapshot missing when recovery from crash (#23496)

It is because write known block only checks block and state without snapshot, which could lead to gap between newest snapshot and newest block state. However, new blocks which would cause snapshot to become fixed were ignored, since state was already known. 


Co-authored-by: Gary Rong <garyrong0905@gmail.com>
Co-authored-by: Martin Holst Swende <martin@swende.se>

core/blockchain_repair_test.go

@@ -1863,3 +1863,124 @@ func testRepair(t *testing.T, tt *rewindTest, snapshots bool) {
 		t.Errorf("Frozen block count mismatch: have %d, want %d", frozen, tt.expFrozen)
 	}
 }
+
+// TestIssue23496 tests scenario described in https://github.com/ethereum/go-ethereum/pull/23496#issuecomment-926393893
+// Credits to @zzyalbert for finding the issue.
+//
+// Local chain owns these blocks:
+// G  B1  B2  B3  B4
+// B1: state committed
+// B2: snapshot disk layer
+// B3: state committed
+// B4: head block
+//
+// Crash happens without fully persisting snapshot and in-memory states,
+// chain rewinds itself to the B1 (skip B3 in order to recover snapshot)
+// In this case the snapshot layer of B3 is not created because of existent
+// state.
+func TestIssue23496(t *testing.T) {
+	// It's hard to follow the test case, visualize the input
+	//log.Root().SetHandler(log.LvlFilterHandler(log.LvlTrace, log.StreamHandler(os.Stderr, log.TerminalFormat(true))))
+
+	// Create a temporary persistent database
+	datadir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("Failed to create temporary datadir: %v", err)
+	}
+	os.RemoveAll(datadir)
+
+	db, err := rawdb.NewLevelDBDatabaseWithFreezer(datadir, 0, 0, datadir, "", false)
+	if err != nil {
+		t.Fatalf("Failed to create persistent database: %v", err)
+	}
+	defer db.Close() // Might double close, should be fine
+
+	// Initialize a fresh chain
+	var (
+		genesis = (&Genesis{BaseFee: big.NewInt(params.InitialBaseFee)}).MustCommit(db)
+		engine  = ethash.NewFullFaker()
+		config  = &CacheConfig{
+			TrieCleanLimit: 256,
+			TrieDirtyLimit: 256,
+			TrieTimeLimit:  5 * time.Minute,
+			SnapshotLimit:  256,
+			SnapshotWait:   true,
+		}
+	)
+	chain, err := NewBlockChain(db, config, params.AllEthashProtocolChanges, engine, vm.Config{}, nil, nil)
+	if err != nil {
+		t.Fatalf("Failed to create chain: %v", err)
+	}
+	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, rawdb.NewMemoryDatabase(), 4, func(i int, b *BlockGen) {
+		b.SetCoinbase(common.Address{0x02})
+		b.SetDifficulty(big.NewInt(1000000))
+	})
+
+	// Insert block B1 and commit the state into disk
+	if _, err := chain.InsertChain(blocks[:1]); err != nil {
+		t.Fatalf("Failed to import canonical chain start: %v", err)
+	}
+	chain.stateCache.TrieDB().Commit(blocks[0].Root(), true, nil)
+
+	// Insert block B2 and commit the snapshot into disk
+	if _, err := chain.InsertChain(blocks[1:2]); err != nil {
+		t.Fatalf("Failed to import canonical chain start: %v", err)
+	}
+	if err := chain.snaps.Cap(blocks[1].Root(), 0); err != nil {
+		t.Fatalf("Failed to flatten snapshots: %v", err)
+	}
+
+	// Insert block B3 and commit the state into disk
+	if _, err := chain.InsertChain(blocks[2:3]); err != nil {
+		t.Fatalf("Failed to import canonical chain start: %v", err)
+	}
+	chain.stateCache.TrieDB().Commit(blocks[2].Root(), true, nil)
+
+	// Insert the remaining blocks
+	if _, err := chain.InsertChain(blocks[3:]); err != nil {
+		t.Fatalf("Failed to import canonical chain tail: %v", err)
+	}
+
+	// Pull the plug on the database, simulating a hard crash
+	db.Close()
+
+	// Start a new blockchain back up and see where the repair leads us
+	db, err = rawdb.NewLevelDBDatabaseWithFreezer(datadir, 0, 0, datadir, "", false)
+	if err != nil {
+		t.Fatalf("Failed to reopen persistent database: %v", err)
+	}
+	defer db.Close()
+
+	chain, err = NewBlockChain(db, nil, params.AllEthashProtocolChanges, engine, vm.Config{}, nil, nil)
+	if err != nil {
+		t.Fatalf("Failed to recreate chain: %v", err)
+	}
+	defer chain.Stop()
+
+	if head := chain.CurrentHeader(); head.Number.Uint64() != uint64(4) {
+		t.Errorf("Head header mismatch: have %d, want %d", head.Number, 4)
+	}
+	if head := chain.CurrentFastBlock(); head.NumberU64() != uint64(4) {
+		t.Errorf("Head fast block mismatch: have %d, want %d", head.NumberU64(), uint64(4))
+	}
+	if head := chain.CurrentBlock(); head.NumberU64() != uint64(1) {
+		t.Errorf("Head block mismatch: have %d, want %d", head.NumberU64(), uint64(1))
+	}
+
+	// Reinsert B2-B4
+	if _, err := chain.InsertChain(blocks[1:]); err != nil {
+		t.Fatalf("Failed to import canonical chain tail: %v", err)
+	}
+	if head := chain.CurrentHeader(); head.Number.Uint64() != uint64(4) {
+		t.Errorf("Head header mismatch: have %d, want %d", head.Number, 4)
+	}
+	if head := chain.CurrentFastBlock(); head.NumberU64() != uint64(4) {
+		t.Errorf("Head fast block mismatch: have %d, want %d", head.NumberU64(), uint64(4))
+	}
+	if head := chain.CurrentBlock(); head.NumberU64() != uint64(4) {
+		t.Errorf("Head block mismatch: have %d, want %d", head.NumberU64(), uint64(4))
+	}
+	if layer := chain.Snapshots().Snapshot(blocks[2].Root()); layer == nil {
+		t.Error("Failed to regenerate the snapshot of known state")
+	}
+}