mysqlctl: Improve backup restore compatibility check

go/vt/mysqlctl/backup_test.go

@@ -423,18 +423,6 @@ func TestRestoreManifestMySQLVersionValidation(t *testing.T) {
 		upgradeSafe            bool
 		wantErr                bool
 	}{
-		{
-			fromVersion: "mysqld  Ver 5.6.42",
-			toVersion:   "mysqld  Ver 5.7.40",
-			upgradeSafe: false,
-			wantErr:     true,
-		},
-		{
-			fromVersion: "mysqld  Ver 5.6.42",
-			toVersion:   "mysqld  Ver 5.7.40",
-			upgradeSafe: true,
-			wantErr:     false,
-		},
 		{
 			fromVersion: "mysqld  Ver 5.7.42",
 			toVersion:   "mysqld  Ver 8.0.32",

go/vt/mysqlctl/backupengine.go

@@ -592,6 +592,15 @@ func FindBackupToRestore(ctx context.Context, params RestoreParams, bhs []backup
 	return restorePath, nil
 }
 
+// See https://github.com/mysql/mysql-server/commit/9a940abe085fc75e1ffe7b72286927fdc9f11207 for the
+// importance of this specific version and why downgrades within patches are allowed since that version.
+var mysql8035 = ServerVersion{Major: 8, Minor: 0, Patch: 35}
+var ltsVersions = []ServerVersion{
+	{Major: 5, Minor: 7, Patch: 0},
+	{Major: 8, Minor: 0, Patch: 0},
+	{Major: 8, Minor: 4, Patch: 0},
+}
+
 func validateMySQLVersionUpgradeCompatible(to string, from string, upgradeSafe bool) error {
 	// It's always safe to use the same version.
 	if to == from {
@@ -616,6 +625,48 @@ func validateMySQLVersionUpgradeCompatible(to string, from string, upgradeSafe b
 		return nil
 	}
 
+	// If we're not on the same LTS stream, we have to do additional checks to see if it's safe to
+	// to upgrade. It can only be one newer LTS version for the destination and the backup
+	// has to be marked as upgrade safe.
+
+	// If something is across different LTS streams and not upgrade safe, we can't use it.
+	if !parsedFrom.isSameRelease(parsedTo) {
+		if !upgradeSafe {
+			if parsedTo.atLeast(parsedFrom) {
+				return fmt.Errorf("running MySQL version %q is newer than backup MySQL version %q which is not safe to upgrade", to, from)
+			}
+			return fmt.Errorf("running MySQL version %q is older than backup MySQL version %q", to, from)
+		}
+
+		// Alright, we're across different LTS streams and the backup is upgrade safe.
+		// We can only upgrade to the next LTS version.
+		for i, ltsVersion := range ltsVersions {
+			if parsedFrom.isSameRelease(ltsVersion) {
+				if i < len(ltsVersions)-1 && parsedTo.isSameRelease(ltsVersions[i+1]) {
+					return nil
+				}
+				if parsedTo.atLeast(parsedFrom) {
+					return fmt.Errorf("running MySQL version %q is too new for backup MySQL version %q", to, from)
+				}
+				return fmt.Errorf("running MySQL version %q is older than backup MySQL version %q", to, from)
+			}
+		}
+		if parsedTo.atLeast(parsedFrom) {
+			return fmt.Errorf("running MySQL version %q is newer than backup MySQL version %q which is not safe to upgrade", to, from)
+		}
+		return fmt.Errorf("running MySQL version %q is older than backup MySQL version %q", to, from)
+	}
+
+	// At this point we know the versions are not the same, but we're withing the same version stream
+	// and only the patch version number mismatches.
+
+	// Starting with MySQL 8.0.35, the data dictionary format is stable for 8.0.x, so we can upgrade
+	// from 8.0.35 or later here, also if the backup was taken with innodb_fast_shutdown=0.
+	// This also applies for any version newer like 8.4.x.
+	if parsedFrom.atLeast(mysql8035) && parsedTo.atLeast(mysql8035) {
+		return nil
+	}
+
 	if !parsedTo.atLeast(parsedFrom) {
 		return fmt.Errorf("running MySQL version %q is older than backup MySQL version %q", to, from)
 	}

go/vt/mysqlctl/backupengine_test.go

@@ -0,0 +1,215 @@
+package mysqlctl
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestValidateMySQLVersionUpgradeCompatible(t *testing.T) {
+	// Test that the MySQL version is compatible with the upgrade.
+	testCases := []struct {
+		name        string
+		fromVersion string
+		toVersion   string
+		upgradeSafe bool
+		error       string
+	}{
+		{
+			name:        "upgrade from 5.7 to 8.0",
+			fromVersion: "mysqld  Ver 5.7.35",
+			toVersion:   "mysqld  Ver 8.0.23",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.0 to 5.7",
+			fromVersion: "mysqld  Ver 8.0.23",
+			toVersion:   "mysqld  Ver 5.7.35",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 5.7.35" is older than backup MySQL version "mysqld  Ver 8.0.23"`,
+		},
+		{
+			name:        "upgrade from 5.7 to 8.0",
+			fromVersion: "mysqld  Ver 5.7.35",
+			toVersion:   "mysqld  Ver 8.0.23",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.23" is newer than backup MySQL version "mysqld  Ver 5.7.35" which is not safe to upgrade`,
+		},
+		{
+			name:        "downgrade from 8.0 to 5.7",
+			fromVersion: "mysqld  Ver 8.0.23",
+			toVersion:   "mysqld  Ver 5.7.35",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 5.7.35" is older than backup MySQL version "mysqld  Ver 8.0.23"`,
+		},
+		{
+			name:        "upgrade from 8.0.23 to 8.0.34",
+			fromVersion: "mysqld  Ver 8.0.23",
+			toVersion:   "mysqld  Ver 8.0.34",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.0.34 to 8.0.23",
+			fromVersion: "mysqld  Ver 8.0.34",
+			toVersion:   "mysqld  Ver 8.0.23",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 8.0.23" is older than backup MySQL version "mysqld  Ver 8.0.34"`,
+		},
+		{
+			name:        "upgrade from 8.0.23 to 8.0.34",
+			fromVersion: "mysqld  Ver 8.0.23",
+			toVersion:   "mysqld  Ver 8.0.34",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.34" is newer than backup MySQL version "mysqld  Ver 8.0.23" which is not safe to upgrade`,
+		},
+		{
+			name:        "downgrade from 8.0.34 to 8.0.23",
+			fromVersion: "mysqld  Ver 8.0.34",
+			toVersion:   "mysqld  Ver 8.0.23",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.23" is older than backup MySQL version "mysqld  Ver 8.0.34"`,
+		},
+		{
+			name:        "upgrade from 8.0.32 to 8.0.36",
+			fromVersion: "mysqld  Ver 8.0.32",
+			toVersion:   "mysqld  Ver 8.0.36",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.0.36 to 8.0.32",
+			fromVersion: "mysqld  Ver 8.0.36",
+			toVersion:   "mysqld  Ver 8.0.32",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 8.0.32" is older than backup MySQL version "mysqld  Ver 8.0.36"`,
+		},
+		{
+			name:        "upgrade from 8.0.32 to 8.0.36",
+			fromVersion: "mysqld  Ver 8.0.32",
+			toVersion:   "mysqld  Ver 8.0.36",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.36" is newer than backup MySQL version "mysqld  Ver 8.0.32" which is not safe to upgrade`,
+		},
+		{
+			name:        "downgrade from 8.0.36 to 8.0.32",
+			fromVersion: "mysqld  Ver 8.0.36",
+			toVersion:   "mysqld  Ver 8.0.32",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.32" is older than backup MySQL version "mysqld  Ver 8.0.36"`,
+		},
+		{
+			name:        "upgrade from 8.0.35 to 8.0.36",
+			fromVersion: "mysqld  Ver 8.0.35",
+			toVersion:   "mysqld  Ver 8.0.36",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.0.36 to 8.0.35",
+			fromVersion: "mysqld  Ver 8.0.36",
+			toVersion:   "mysqld  Ver 8.0.35",
+			upgradeSafe: true,
+		},
+		{
+			name:        "upgrade from 8.0.35 to 8.0.36",
+			fromVersion: "mysqld  Ver 8.0.35",
+			toVersion:   "mysqld  Ver 8.0.36",
+			upgradeSafe: false,
+		},
+		{
+			name:        "downgrade from 8.0.36 to 8.0.35",
+			fromVersion: "mysqld  Ver 8.0.36",
+			toVersion:   "mysqld  Ver 8.0.35",
+			upgradeSafe: false,
+		},
+		{
+			name:        "upgrade from 8.4.0 to 8.4.1",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 8.4.1",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.4.1 to 8.4.0",
+			fromVersion: "mysqld  Ver 8.4.1",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: true,
+		},
+		{
+			name:        "upgrade from 8.4.0 to 8.4.1",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 8.4.1",
+			upgradeSafe: false,
+		},
+		{
+			name:        "downgrade from 8.4.1 to 8.4.0",
+			fromVersion: "mysqld  Ver 8.4.1",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: false,
+		},
+		{
+			name:        "upgrade from 8.0.35 to 8.4.0",
+			fromVersion: "mysqld  Ver 8.0.32",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: true,
+		},
+		{
+			name:        "downgrade from 8.4.0 to 8.0.32",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 8.0.32",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 8.0.32" is older than backup MySQL version "mysqld  Ver 8.4.0"`,
+		},
+		{
+			name:        "upgrade from 8.0.32 to 8.4.0",
+			fromVersion: "mysqld  Ver 8.0.32",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.4.0" is newer than backup MySQL version "mysqld  Ver 8.0.32" which is not safe to upgrade`,
+		},
+		{
+			name:        "downgrade from 8.4.0 to 8.0.32",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 8.0.32",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.0.32" is older than backup MySQL version "mysqld  Ver 8.4.0"`,
+		},
+		{
+			name:        "upgrade from 5.7.35 to 8.4.0",
+			fromVersion: "mysqld  Ver 5.7.32",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 8.4.0" is too new for backup MySQL version "mysqld  Ver 5.7.32"`,
+		},
+		{
+			name:        "downgrade from 8.4.0 to 5.7.32",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 5.7.32",
+			upgradeSafe: true,
+			error:       `running MySQL version "mysqld  Ver 5.7.32" is older than backup MySQL version "mysqld  Ver 8.4.0"`,
+		},
+		{
+			name:        "upgrade from 5.7.32 to 8.4.0",
+			fromVersion: "mysqld  Ver 5.7.32",
+			toVersion:   "mysqld  Ver 8.4.0",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 8.4.0" is newer than backup MySQL version "mysqld  Ver 5.7.32" which is not safe to upgrade`,
+		},
+		{
+			name:        "downgrade from 8.4.0 to 5.7.32",
+			fromVersion: "mysqld  Ver 8.4.0",
+			toVersion:   "mysqld  Ver 5.7.32",
+			upgradeSafe: false,
+			error:       `running MySQL version "mysqld  Ver 5.7.32" is older than backup MySQL version "mysqld  Ver 8.4.0"`,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := validateMySQLVersionUpgradeCompatible(tc.toVersion, tc.fromVersion, tc.upgradeSafe)
+			if tc.error == "" {
+				assert.NoError(t, err)
+			} else {
+				assert.EqualError(t, err, tc.error)
+			}
+		})
+	}
+
+}

go/vt/mysqlctl/version.go

@@ -36,3 +36,7 @@ func (v *ServerVersion) atLeast(compare ServerVersion) bool {
 	}
 	return false
 }
+
+func (v *ServerVersion) isSameRelease(compare ServerVersion) bool {
+	return v.Major == compare.Major && v.Minor == compare.Minor
+}