add switch_helper

internal/app/app.go

@@ -38,6 +38,7 @@ type App struct {
 	daemonMutex         sync.Mutex
 	replRepairState     map[string]*ReplicationRepairState
 	externalReplication mysql.IExternalReplication
+	switchHelper 		mysql.ISwitchHelper
 }
 
 // NewApp returns new App. Suddenly.
@@ -62,6 +63,7 @@ func NewApp(configFile, logLevel string, interactive bool) (*App, error) {
 	if err != nil {
 		return nil, err
 	}
+	switchHelper := mysql.NewSwitchHelper(config, logger)
 	app := &App{
 		state:               stateFirstRun,
 		config:              config,
@@ -70,6 +72,7 @@ func NewApp(configFile, logLevel string, interactive bool) (*App, error) {
 		streamFromFailedAt:  make(map[string]time.Time),
 		replRepairState:     make(map[string]*ReplicationRepairState),
 		externalReplication: externalReplication,
+		switchHelper: switchHelper,
 	}
 	return app, nil
 }
@@ -1274,13 +1277,8 @@ func (app *App) performSwitchover(clusterState map[string]*NodeState, activeNode
 		newMaster = switchover.To
 	} else if switchover.From != "" {
 		positions2 := filterOutNodeFromPositions(positions, switchover.From)
-		PriorityChoiceMaxLag := app.config.PriorityChoiceMaxLag
-		AsyncAllowedLagTime := time.Duration(app.config.AsyncAllowedLag) * time.Second
-		if app.config.ASync && switchover.Cause == CauseAuto && AsyncAllowedLagTime > app.config.PriorityChoiceMaxLag {
-			PriorityChoiceMaxLag = AsyncAllowedLagTime
-		}
 		// we ignore splitbrain flag as it should be handled during searching most recent host
-		newMaster, err = getMostDesirableNode(app.logger, positions2, PriorityChoiceMaxLag)
+		newMaster, err = getMostDesirableNode(app.logger, positions2, app.switchHelper.GetPriorityChoiceMaxLag())
 		if err != nil {
 			return fmt.Errorf("switchover: error while looking for highest priority node: %s", switchover.From)
 		}

internal/app/cli.go

@@ -280,7 +280,7 @@ func (app *App) CliSwitch(switchFrom, switchTo string, waitTimeout time.Duration
 				app.logger.Errorf(err.Error())
 				return 1
 			}
-			toHost, err = getMostDesirableNode(app.logger, positions, app.config.PriorityChoiceMaxLag)
+			toHost, err = getMostDesirableNode(app.logger, positions, app.switchHelper.GetPriorityChoiceMaxLag())
 			if err != nil {
 				app.logger.Errorf(err.Error())
 				return 1

internal/mysql/switch_helper.go

@@ -0,0 +1,42 @@
+package mysql
+
+import (
+	"time"
+
+	"github.com/yandex/mysync/internal/config"
+)
+
+type ISwitchHelper interface {
+	GetPriorityChoiceMaxLag() time.Duration
+}
+
+type DefaultSwitchHelper struct {
+	config *config.Config
+}
+
+type AsyncSwitchHelper struct {
+	config *config.Config
+}
+
+func NewSwitchHelper(config *config.Config) ISwitchHelper {
+	if config.ASync {
+		return &AsyncSwitchHelper{
+			config: config,
+		}
+	}
+	return &DefaultSwitchHelper{
+		config: config,
+	}
+}
+
+func (sh *DefaultSwitchHelper) GetPriorityChoiceMaxLag() time.Duration {
+	return sh.config.PriorityChoiceMaxLag
+}
+
+func (sh *AsyncSwitchHelper) GetPriorityChoiceMaxLag() time.Duration {
+	AsyncAllowedLagTime := time.Duration(sh.config.AsyncAllowedLag) * time.Second
+	if AsyncAllowedLagTime > sh.config.PriorityChoiceMaxLag {
+		return AsyncAllowedLagTime
+	}
+	return sh.config.PriorityChoiceMaxLag
+}