core/rawdb: enforce readonly in freezer instantiation (ethereum#24119)

* freezer: add readonly flag to table

* freezer: enforce readonly in table repair

* freezer: enforce readonly in newFreezer

* minor fix

* minor

* core/rawdb: test that writing during readonly fails

* rm unused log

* check readonly on batch append

* minor

* Revert "check readonly on batch append"

This reverts commit 2ddb5ec.

* review fixes

* minor test refactor

* attempt at fixing windows issue

* add comment re windows sync issue

* k->kind

* open readonly db for genesis check

Co-authored-by: Martin Holst Swende <martin@swende.se>

cmd/geth/dbcmd.go

@@ -555,7 +555,7 @@ func freezerInspect(ctx *cli.Context) error {
 	defer stack.Close()
 	path := filepath.Join(stack.ResolvePath("chaindata"), "ancient")
 	log.Info("Opening freezer", "location", path, "name", kind)
-	if f, err := rawdb.NewFreezerTable(path, kind, disableSnappy); err != nil {
+	if f, err := rawdb.NewFreezerTable(path, kind, disableSnappy, true); err != nil {
 		return err
 	} else {
 		f.DumpIndex(start, end)

cmd/utils/flags.go

@@ -1719,7 +1719,7 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 		if ctx.GlobalIsSet(DataDirFlag.Name) {
 			// Check if we have an already initialized chain and fall back to
 			// that if so. Otherwise we need to generate a new genesis spec.
-			chaindb := MakeChainDatabase(ctx, stack, false) // TODO (MariusVanDerWijden) make this read only
+			chaindb := MakeChainDatabase(ctx, stack, true)
 			if rawdb.ReadCanonicalHash(chaindb, 0) != (common.Hash{}) {
 				cfg.Genesis = nil // fallback to db content
 			}

core/rawdb/freezer.go

@@ -133,7 +133,7 @@ func newFreezer(datadir string, namespace string, readonly bool, maxTableSize ui
 
 	// Create the tables.
 	for name, disableSnappy := range tables {
-		table, err := newTable(datadir, name, readMeter, writeMeter, sizeGauge, maxTableSize, disableSnappy)
+		table, err := newTable(datadir, name, readMeter, writeMeter, sizeGauge, maxTableSize, disableSnappy, readonly)
 		if err != nil {
 			for _, table := range freezer.tables {
 				table.Close()
@@ -144,8 +144,15 @@ func newFreezer(datadir string, namespace string, readonly bool, maxTableSize ui
 		freezer.tables[name] = table
 	}
 
-	// Truncate all tables to common length.
-	if err := freezer.repair(); err != nil {
+	if freezer.readonly {
+		// In readonly mode only validate, don't truncate.
+		// validate also sets `freezer.frozen`.
+		err = freezer.validate()
+	} else {
+		// Truncate all tables to common length.
+		err = freezer.repair()
+	}
+	if err != nil {
 		for _, table := range freezer.tables {
 			table.Close()
 		}
@@ -308,6 +315,33 @@ func (f *freezer) Sync() error {
 	return nil
 }
 
+// validate checks that every table has the same length.
+// Used instead of `repair` in readonly mode.
+func (f *freezer) validate() error {
+	if len(f.tables) == 0 {
+		return nil
+	}
+	var (
+		length uint64
+		name   string
+	)
+	// Hack to get length of any table
+	for kind, table := range f.tables {
+		length = atomic.LoadUint64(&table.items)
+		name = kind
+		break
+	}
+	// Now check every table against that length
+	for kind, table := range f.tables {
+		items := atomic.LoadUint64(&table.items)
+		if length != items {
+			return fmt.Errorf("freezer tables %s and %s have differing lengths: %d != %d", kind, name, items, length)
+		}
+	}
+	atomic.StoreUint64(&f.frozen, length)
+	return nil
+}
+
 // repair truncates all data tables to the same length.
 func (f *freezer) repair() error {
 	min := uint64(math.MaxUint64)

core/rawdb/freezer_table.go

@@ -94,7 +94,8 @@ type freezerTable struct {
 	// so take advantage of that (https://golang.org/pkg/sync/atomic/#pkg-note-BUG).
 	items uint64 // Number of items stored in the table (including items removed from tail)
 
-	noCompression bool   // if true, disables snappy compression. Note: does not work retroactively
+	noCompression bool // if true, disables snappy compression. Note: does not work retroactively
+	readonly      bool
 	maxFileSize   uint32 // Max file size for data-files
 	name          string
 	path          string
@@ -119,8 +120,8 @@ type freezerTable struct {
 }
 
 // NewFreezerTable opens the given path as a freezer table.
-func NewFreezerTable(path, name string, disableSnappy bool) (*freezerTable, error) {
-	return newTable(path, name, metrics.NilMeter{}, metrics.NilMeter{}, metrics.NilGauge{}, freezerTableSize, disableSnappy)
+func NewFreezerTable(path, name string, disableSnappy, readonly bool) (*freezerTable, error) {
+	return newTable(path, name, metrics.NilMeter{}, metrics.NilMeter{}, metrics.NilGauge{}, freezerTableSize, disableSnappy, readonly)
 }
 
 // openFreezerFileForAppend opens a freezer table file and seeks to the end
@@ -164,7 +165,7 @@ func truncateFreezerFile(file *os.File, size int64) error {
 // newTable opens a freezer table, creating the data and index files if they are
 // non existent. Both files are truncated to the shortest common length to ensure
 // they don't go out of sync.
-func newTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter, sizeGauge metrics.Gauge, maxFilesize uint32, noCompression bool) (*freezerTable, error) {
+func newTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter, sizeGauge metrics.Gauge, maxFilesize uint32, noCompression, readonly bool) (*freezerTable, error) {
 	// Ensure the containing directory exists and open the indexEntry file
 	if err := os.MkdirAll(path, 0755); err != nil {
 		return nil, err
@@ -177,7 +178,16 @@ func newTable(path string, name string, readMeter metrics.Meter, writeMeter metr
 		// Compressed idx
 		idxName = fmt.Sprintf("%s.cidx", name)
 	}
-	offsets, err := openFreezerFileForAppend(filepath.Join(path, idxName))
+	var (
+		err     error
+		offsets *os.File
+	)
+	if readonly {
+		// Will fail if table doesn't exist
+		offsets, err = openFreezerFileForReadOnly(filepath.Join(path, idxName))
+	} else {
+		offsets, err = openFreezerFileForAppend(filepath.Join(path, idxName))
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -192,6 +202,7 @@ func newTable(path string, name string, readMeter metrics.Meter, writeMeter metr
 		path:          path,
 		logger:        log.New("database", path, "table", name),
 		noCompression: noCompression,
+		readonly:      readonly,
 		maxFileSize:   maxFilesize,
 	}
 	if err := tab.repair(); err != nil {
@@ -252,7 +263,11 @@ func (t *freezerTable) repair() error {
 
 	t.index.ReadAt(buffer, offsetsSize-indexEntrySize)
 	lastIndex.unmarshalBinary(buffer)
-	t.head, err = t.openFile(lastIndex.filenum, openFreezerFileForAppend)
+	if t.readonly {
+		t.head, err = t.openFile(lastIndex.filenum, openFreezerFileForReadOnly)
+	} else {
+		t.head, err = t.openFile(lastIndex.filenum, openFreezerFileForAppend)
+	}
 	if err != nil {
 		return err
 	}
@@ -301,12 +316,15 @@ func (t *freezerTable) repair() error {
 			contentExp = int64(lastIndex.offset)
 		}
 	}
-	// Ensure all reparation changes have been written to disk
-	if err := t.index.Sync(); err != nil {
-		return err
-	}
-	if err := t.head.Sync(); err != nil {
-		return err
+	// Sync() fails for read-only files on windows.
+	if !t.readonly {
+		// Ensure all reparation changes have been written to disk
+		if err := t.index.Sync(); err != nil {
+			return err
+		}
+		if err := t.head.Sync(); err != nil {
+			return err
+		}
 	}
 	// Update the item and byte counters and return
 	t.items = uint64(t.itemOffset) + uint64(offsetsSize/indexEntrySize-1) // last indexEntry points to the end of the data file
@@ -334,8 +352,12 @@ func (t *freezerTable) preopen() (err error) {
 			return err
 		}
 	}
-	// Open head in read/write
-	t.head, err = t.openFile(t.headId, openFreezerFileForAppend)
+	if t.readonly {
+		t.head, err = t.openFile(t.headId, openFreezerFileForReadOnly)
+	} else {
+		// Open head in read/write
+		t.head, err = t.openFile(t.headId, openFreezerFileForAppend)
+	}
 	return err
 }