cli: Add etcdutl snapshot hashkv command

Signed-off-by: Cenk Alti <cenkalti@gmail.com>

Apply suggestions from code review

Co-authored-by: Benjamin Wang <benjamin.wang@broadcom.com>

etcdutl/README.md

@@ -119,6 +119,44 @@ Prints a line of JSON encoding the database hash, revision, total keys, and size
 +----------+----------+------------+------------+
 ```
 
+### HASHKV [options] \<filename\>
+
+HASHKV prints hash of keys and values up to given revision.
+
+#### Options
+
+- rev -- Revision number. Default is 0 which means the latest revision.
+
+#### Output
+
+##### Simple format
+
+Prints a humanized table of the KV hash, hash revision and compact revision.
+
+##### JSON format
+
+Prints a line of JSON encoding the KV hash, hash revision and compact revision.
+
+#### Examples
+```bash
+./etcdutl hashkv file.db
+# 35c86e9b, 214, 150
+```
+
+```bash
+./etcdutl --write-out=json hashkv file.db
+# {"hash":902327963,"hashRevision":214,"compactRevision":150}
+```
+
+```bash
+./etcdutl --write-out=table hashkv file.db
++----------+---------------+------------------+
+|   HASH   | HASH REVISION | COMPACT REVISION |
++----------+---------------+------------------+
+| 35c86e9b |           214 |              150 |
++----------+---------------+------------------+
+```
+
 ### VERSION
 
 Prints the version of etcdutl.

etcdutl/ctl.go

@@ -43,6 +43,7 @@ func init() {
 	rootCmd.AddCommand(
 		etcdutl.NewDefragCommand(),
 		etcdutl.NewSnapshotCommand(),
+		etcdutl.NewHashKVCommand(),
 		etcdutl.NewVersionCommand(),
 		etcdutl.NewCompletionCommand(),
 		etcdutl.NewMigrateCommand(),

etcdutl/etcdutl/hashkv_command.go

@@ -0,0 +1,74 @@
+// Copyright 2024 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package etcdutl
+
+import (
+	"github.com/spf13/cobra"
+	"go.uber.org/zap"
+
+	"go.etcd.io/etcd/pkg/v3/cobrautl"
+	"go.etcd.io/etcd/server/v3/storage/backend"
+	"go.etcd.io/etcd/server/v3/storage/mvcc"
+)
+
+var (
+	hashKVRevision int64
+)
+
+// NewHashKVCommand returns the cobra command for "hashkv".
+func NewHashKVCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "hashkv <filename>",
+		Short: "Prints the KV history hash of a given file",
+		Args:  cobra.ExactArgs(1),
+		Run:   hashKVCommandFunc,
+	}
+	cmd.Flags().Int64Var(&hashKVRevision, "rev", 0, "maximum revision to hash (default: latest revision)")
+	return cmd
+}
+
+func hashKVCommandFunc(cmd *cobra.Command, args []string) {
+	printer := initPrinterFromCmd(cmd)
+
+	ds, err := calculateHashKV(args[0], hashKVRevision)
+	if err != nil {
+		cobrautl.ExitWithError(cobrautl.ExitError, err)
+	}
+	printer.DBHashKV(ds)
+}
+
+type HashKV struct {
+	Hash            uint32 `json:"hash"`
+	HashRevision    int64  `json:"hashRevision"`
+	CompactRevision int64  `json:"compactRevision"`
+}
+
+func calculateHashKV(dbPath string, rev int64) (HashKV, error) {
+	cfg := backend.DefaultBackendConfig(zap.NewNop())
+	cfg.Path = dbPath
+	b := backend.New(cfg)
+	st := mvcc.NewStore(zap.NewNop(), b, nil, mvcc.StoreConfig{})
+	hst := mvcc.NewHashStorage(zap.NewNop(), st)
+
+	h, _, err := hst.HashByRev(rev)
+	if err != nil {
+		return HashKV{}, err
+	}
+	return HashKV{
+		Hash:            h.Hash,
+		HashRevision:    h.Revision,
+		CompactRevision: h.CompactRevision,
+	}, nil
+}

etcdutl/etcdutl/printer.go

@@ -31,6 +31,7 @@ var (
 
 type printer interface {
 	DBStatus(snapshot.Status)
+	DBHashKV(HashKV)
 }
 
 func NewPrinter(printerType string) printer {
@@ -64,6 +65,7 @@ func newPrinterUnsupported(n string) printer {
 }
 
 func (p *printerUnsupported) DBStatus(snapshot.Status) { p.p(nil) }
+func (p *printerUnsupported) DBHashKV(HashKV)          { p.p(nil) }
 
 func makeDBStatusTable(ds snapshot.Status) (hdr []string, rows [][]string) {
 	hdr = []string{"hash", "revision", "total keys", "total size", "version"}
@@ -77,6 +79,16 @@ func makeDBStatusTable(ds snapshot.Status) (hdr []string, rows [][]string) {
 	return hdr, rows
 }
 
+func makeDBHashKVTable(ds HashKV) (hdr []string, rows [][]string) {
+	hdr = []string{"hash", "hash revision", "compact revision"}
+	rows = append(rows, []string{
+		fmt.Sprint(ds.Hash),
+		fmt.Sprint(ds.HashRevision),
+		fmt.Sprint(ds.CompactRevision),
+	})
+	return hdr, rows
+}
+
 func initPrinterFromCmd(cmd *cobra.Command) (p printer) {
 	outputType, err := cmd.Flags().GetString("write-out")
 	if err != nil {

etcdutl/etcdutl/printer_fields.go

@@ -29,3 +29,9 @@ func (p *fieldsPrinter) DBStatus(r snapshot.Status) {
 	fmt.Println(`"Size" :`, r.TotalSize)
 	fmt.Println(`"Version" :`, r.Version)
 }
+
+func (p *fieldsPrinter) DBHashKV(r HashKV) {
+	fmt.Println(`"Hash" :`, r.Hash)
+	fmt.Println(`"Hash revision" :`, r.HashRevision)
+	fmt.Println(`"Compact revision" :`, r.CompactRevision)
+}

etcdutl/etcdutl/printer_json.go

@@ -33,6 +33,7 @@ func newJSONPrinter() printer {
 }
 
 func (p *jsonPrinter) DBStatus(r snapshot.Status) { printJSON(r) }
+func (p *jsonPrinter) DBHashKV(r HashKV)          { printJSON(r) }
 
 // !!! Share ??
 func printJSON(v any) {

etcdutl/etcdutl/printer_simple.go

@@ -30,3 +30,10 @@ func (s *simplePrinter) DBStatus(ds snapshot.Status) {
 		fmt.Println(strings.Join(row, ", "))
 	}
 }
+
+func (s *simplePrinter) DBHashKV(ds HashKV) {
+	_, rows := makeDBHashKVTable(ds)
+	for _, row := range rows {
+		fmt.Println(strings.Join(row, ", "))
+	}
+}

etcdutl/etcdutl/printer_table.go

@@ -34,3 +34,14 @@ func (tp *tablePrinter) DBStatus(r snapshot.Status) {
 	table.SetAlignment(tablewriter.ALIGN_RIGHT)
 	table.Render()
 }
+
+func (tp *tablePrinter) DBHashKV(r HashKV) {
+	hdr, rows := makeDBHashKVTable(r)
+	table := tablewriter.NewWriter(os.Stdout)
+	table.SetHeader(hdr)
+	for _, row := range rows {
+		table.Append(row)
+	}
+	table.SetAlignment(tablewriter.ALIGN_RIGHT)
+	table.Render()
+}

server/storage/mvcc/hash.go

@@ -111,7 +111,7 @@ type hashStorage struct {
 	lg     *zap.Logger
 }
 
-func newHashStorage(lg *zap.Logger, s *store) *hashStorage {
+func NewHashStorage(lg *zap.Logger, s *store) HashStorage {
 	return &hashStorage{
 		store: s,
 		lg:    lg,

server/storage/mvcc/hash_test.go

@@ -178,8 +178,9 @@ func (tc hashTestCase) Compact(ctx context.Context, rev int64) error {
 
 func TestHasherStore(t *testing.T) {
 	lg := zaptest.NewLogger(t)
-	s := newHashStorage(lg, newFakeStore(lg))
+	store := newFakeStore(lg)
-	defer s.store.Close()
+	s := NewHashStorage(lg, store)
+	defer store.Close()
 
 	var hashes []KeyValueHash
 	for i := 0; i < hashStorageMaxSize; i++ {
@@ -207,8 +208,9 @@ func TestHasherStore(t *testing.T) {
 
 func TestHasherStoreFull(t *testing.T) {
 	lg := zaptest.NewLogger(t)
-	s := newHashStorage(lg, newFakeStore(lg))
+	store := newFakeStore(lg)
-	defer s.store.Close()
+	s := NewHashStorage(lg, store)
+	defer store.Close()
 
 	var minRevision int64 = 100
 	var maxRevision = minRevision + hashStorageMaxSize

server/storage/mvcc/kvstore.go

@@ -106,7 +106,7 @@ func NewStore(lg *zap.Logger, b backend.Backend, le lease.Lessor, cfg StoreConfi
 
 		lg: lg,
 	}
-	s.hashes = newHashStorage(lg, s)
+	s.hashes = NewHashStorage(lg, s)
 	s.ReadView = &readView{s}
 	s.WriteView = &writeView{s}
 	if s.le != nil {

server/storage/mvcc/kvstore_test.go

@@ -929,7 +929,7 @@ func newFakeStore(lg *zap.Logger) *store {
 		lg:             lg,
 	}
 	s.ReadView, s.WriteView = &readView{s}, &writeView{s}
-	s.hashes = newHashStorage(lg, s)
+	s.hashes = NewHashStorage(lg, s)
 	return s
 }