Merge validator databases (#5968)

* merge functionality

* merge testing

* log info when merge completed successfully

* extracted private methods

* fixed linter errors

* fixed compilation errors

* build files clean-up

* fixed failing test

* corrected command description

* close sources inside defer

* corrected documentation of NewKVStore

validator/accounts/BUILD.bazel

@@ -17,6 +17,7 @@ go_library(
         "//shared/cmd:go_default_library",
         "//shared/keystore:go_default_library",
         "//shared/params:go_default_library",
+        "//validator/db:go_default_library",
         "//validator/flags:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
         "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
@@ -35,13 +36,17 @@ go_test(
     ],
     embed = [":go_default_library"],
     deps = [
+        "//proto/slashing:go_default_library",
         "//shared/keystore:go_default_library",
         "//shared/mock:go_default_library",
         "//shared/params:go_default_library",
         "//shared/testutil:go_default_library",
+        "//validator/db:go_default_library",
         "//validator/flags:go_default_library",
         "@com_github_golang_mock//gomock:go_default_library",
+        "@com_github_pkg_errors//:go_default_library",
         "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
+        "@com_github_prysmaticlabs_go_bitfield//:go_default_library",
         "@in_gopkg_urfave_cli_v2//:go_default_library",
     ],
 )

validator/accounts/account.go

@@ -3,6 +3,7 @@ package accounts
 
 import (
 	"bufio"
+	"context"
 	"encoding/hex"
 	"fmt"
 	"io"
@@ -17,6 +18,7 @@ import (
 	"github.com/prysmaticlabs/prysm/shared/cmd"
 	"github.com/prysmaticlabs/prysm/shared/keystore"
 	"github.com/prysmaticlabs/prysm/shared/params"
+	"github.com/prysmaticlabs/prysm/validator/db"
 	"github.com/prysmaticlabs/prysm/validator/flags"
 	"github.com/sirupsen/logrus"
 	"gopkg.in/urfave/cli.v2"
@@ -118,7 +120,7 @@ func NewValidatorAccount(directory string, password string) error {
 }
 
 // Exists checks if a validator account at a given keystore path exists.
-// assertNonEmpty is a boolean used to determine whether to check that 
+// assertNonEmpty is a boolean used to determine whether to check that
 // the provided directory exists.
 func Exists(keystorePath string, assertNonEmpty bool) (bool, error) {
 	/* #nosec */
@@ -219,6 +221,41 @@ func HandleEmptyKeystoreFlags(cliCtx *cli.Context, confirmPassword bool) (string
 	return path, passphrase, nil
 }
 
+// Merge merges data from validator databases in sourceDirectories into a new store, which is created in targetDirectory.
+func Merge(ctx context.Context, sourceDirectories []string, targetDirectory string) error {
+	var sourceStores []*db.Store
+
+	for _, dir := range sourceDirectories {
+		store, err := db.GetKVStore(dir)
+		if err != nil {
+			return errors.Wrapf(err, "Failed to prepare the database in %s for merging", dir)
+		}
+		if store == nil {
+			continue
+		}
+		sourceStores = append(sourceStores, store)
+	}
+
+	if len(sourceStores) == 0 {
+		return errors.New("no validator databases found in source directories")
+	}
+
+	err := db.Merge(ctx, sourceStores, targetDirectory)
+	if err != nil {
+		return errors.Wrapf(err, "Failed to merge validator databases into %s", targetDirectory)
+	}
+
+	defer func() {
+		for _, store := range sourceStores {
+			if err := store.Close(); err != nil {
+				err = errors.Wrapf(err, "Failed to close the database in %s", store.DatabasePath())
+			}
+		}
+	}()
+
+	return nil
+}
+
 // ChangePassword changes the password for all keys located in a keystore.
 // Password is changed only for keys that can be decrypted using the old password.
 func ChangePassword(keystorePath string, oldPassword string, newPassword string) error {