Added lease duration option

options.go

@@ -17,6 +17,10 @@ const (
 	minMaxEntriesPerRPC     = 50
 	maxMaxEntriesPerRPC     = 500
 	defaultMaxEntriesPerRPC = 100
+
+	minLeaseDuration     = time.Duration(25 * time.Millisecond)
+	maxLeaseDuration     = time.Duration(1000 * time.Millisecond)
+	defaultLeaseDuration = time.Duration(300 * time.Millisecond)
 )
 
 // Logger supports logging messages at the debug, info, warn, error, and fatal level.
@@ -66,6 +70,9 @@ type options struct {
 	// an AppendEntries RPC.
 	maxEntriesPerRPC int
 
+	// The duration that a lease remains valid upon renewal.
+	leaseDuration time.Duration
+
 	// A logger for debugging and important events.
 	logger Logger
 }
@@ -107,6 +114,21 @@ func WithMaxEntriesPerRPC(maxEntriesPerRPC int) Option {
 	}
 }
 
+// WithLeaseDuration sets the duration for which a lease remains valid upon
+// renewal. A longer lease duration generally corresponds to higher performance
+// of read-only operations but increases the likelihood that stale data is read.
+// Likewise, a shorter lease duration corresponds to lesser performance of read-only
+// operations but decreases the likelihood of stale data being read.
+func WithLeaseDuration(leaseDuration time.Duration) Option {
+	return func(options *options) error {
+		if leaseDuration < minLeaseDuration || leaseDuration > maxLeaseDuration {
+			return errors.New("lease duration is invalid")
+		}
+		options.leaseDuration = leaseDuration
+		return nil
+	}
+}
+
 // WithLogger sets the logger used by the Raft server.
 func WithLogger(logger Logger) Option {
 	return func(options *options) error {