RetryConfig: Add MaxBackoff option (fixes #938)

config/consul_test.go

@@ -249,9 +249,10 @@ func TestConsulConfig_Finalize(t *testing.T) {
 					Password: String(""),
 				},
 				Retry: &RetryConfig{
-					Backoff:  TimeDuration(DefaultRetryBackoff),
-					Enabled:  Bool(true),
-					Attempts: Int(DefaultRetryAttempts),
+					Backoff:    TimeDuration(DefaultRetryBackoff),
+					MaxBackoff: TimeDuration(DefaultRetryMaxBackoff),
+					Enabled:    Bool(true),
+					Attempts:   Int(DefaultRetryAttempts),
 				},
 				SSL: &SSLConfig{
 					CaCert:     String(""),

config/retry.go

@@ -13,6 +13,9 @@ const (
 	// DefaultRetryBackoff is the default base for the exponential backoff
 	// algorithm.
 	DefaultRetryBackoff = 250 * time.Millisecond
+
+	// DefaultRetryMaxBackoff is the default maximum of backoff time
+	DefaultRetryMaxBackoff = 0 * time.Millisecond
 )
 
 // RetryFunc is the signature of a function that supports retries.
@@ -23,12 +26,17 @@ type RetryFunc func(int) (bool, time.Duration)
 type RetryConfig struct {
 	// Attempts is the total number of maximum attempts to retry before letting
 	// the error fall through.
+	// 0 means unlimited.
 	Attempts *int
 
 	// Backoff is the base of the exponentialbackoff. This number will be
 	// multipled by the next power of 2 on each iteration.
 	Backoff *time.Duration
 
+	// MaxBackoff is an upper limit the result of the sleep time between retries
+	// A MaxBackoff of zero means there is no limit to the exponential growth of the backoff.
+	MaxBackoff *time.Duration
+
 	// Enabled signals if this retry is enabled.
 	Enabled *bool
 }
@@ -51,6 +59,8 @@ func (c *RetryConfig) Copy() *RetryConfig {
 
 	o.Backoff = c.Backoff
 
+	o.MaxBackoff = c.MaxBackoff
+
 	o.Enabled = c.Enabled
 
 	return &o
@@ -82,6 +92,10 @@ func (c *RetryConfig) Merge(o *RetryConfig) *RetryConfig {
 		r.Backoff = o.Backoff
 	}
 
+	if o.MaxBackoff != nil {
+		r.MaxBackoff = o.MaxBackoff
+	}
+
 	if o.Enabled != nil {
 		r.Enabled = o.Enabled
 	}
@@ -103,6 +117,11 @@ func (c *RetryConfig) RetryFunc() RetryFunc {
 		base := math.Pow(2, float64(retry))
 		sleep := time.Duration(base) * TimeDurationVal(c.Backoff)
 
+		maxSleep := TimeDurationVal(c.MaxBackoff)
+		if maxSleep > 0 && maxSleep < sleep {
+			return true, maxSleep
+		}
+
 		return true, sleep
 	}
 }
@@ -117,6 +136,10 @@ func (c *RetryConfig) Finalize() {
 		c.Backoff = TimeDuration(DefaultRetryBackoff)
 	}
 
+	if c.MaxBackoff == nil {
+		c.MaxBackoff = TimeDuration(DefaultRetryMaxBackoff)
+	}
+
 	if c.Enabled == nil {
 		c.Enabled = Bool(true)
 	}
@@ -131,10 +154,12 @@ func (c *RetryConfig) GoString() string {
 	return fmt.Sprintf("&RetryConfig{"+
 		"Attempts:%s, "+
 		"Backoff:%s, "+
+		"MaxBackoff:%s, "+
 		"Enabled:%s"+
 		"}",
 		IntGoString(c.Attempts),
 		TimeDurationGoString(c.Backoff),
+		TimeDurationGoString(c.MaxBackoff),
 		BoolGoString(c.Enabled),
 	)
 }

config/retry_test.go

@@ -28,6 +28,15 @@ func TestRetryConfig_Copy(t *testing.T) {
 				Enabled:  Bool(true),
 			},
 		},
+		{
+			"max_backoff",
+			&RetryConfig{
+				Attempts:   Int(0),
+				Backoff:    TimeDuration(20 * time.Second),
+				MaxBackoff: TimeDuration(100 * time.Second),
+				Enabled:    Bool(true),
+			},
+		},
 	}
 
 	for i, tc := range cases {
@@ -120,6 +129,32 @@ func TestRetryConfig_Merge(t *testing.T) {
 			&RetryConfig{Backoff: TimeDuration(10 * time.Second)},
 			&RetryConfig{Backoff: TimeDuration(10 * time.Second)},
 		},
+
+		{
+			"maxbackoff_overrides",
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+			&RetryConfig{MaxBackoff: TimeDuration(20 * time.Second)},
+			&RetryConfig{MaxBackoff: TimeDuration(20 * time.Second)},
+		},
+		{
+			"maxbackoff_empty_one",
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+			&RetryConfig{},
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+		},
+		{
+			"maxbackoff_empty_two",
+			&RetryConfig{},
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+		},
+		{
+			"maxbackoff_same",
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+			&RetryConfig{MaxBackoff: TimeDuration(10 * time.Second)},
+		},
+
 		{
 			"enabled_overrides",
 			&RetryConfig{Enabled: Bool(true)},
@@ -166,9 +201,10 @@ func TestRetryConfig_Finalize(t *testing.T) {
 			"empty",
 			&RetryConfig{},
 			&RetryConfig{
-				Attempts: Int(DefaultRetryAttempts),
-				Backoff:  TimeDuration(DefaultRetryBackoff),
-				Enabled:  Bool(true),
+				Attempts:   Int(DefaultRetryAttempts),
+				Backoff:    TimeDuration(DefaultRetryBackoff),
+				MaxBackoff: TimeDuration(DefaultRetryMaxBackoff),
+				Enabled:    Bool(true),
 			},
 		},
 	}

config/vault_test.go

@@ -298,9 +298,10 @@ func TestVaultConfig_Finalize(t *testing.T) {
 				Enabled:    Bool(false),
 				RenewToken: Bool(DefaultVaultRenewToken),
 				Retry: &RetryConfig{
-					Backoff:  TimeDuration(DefaultRetryBackoff),
-					Enabled:  Bool(true),
-					Attempts: Int(DefaultRetryAttempts),
+					Backoff:    TimeDuration(DefaultRetryBackoff),
+					MaxBackoff: TimeDuration(DefaultRetryMaxBackoff),
+					Enabled:    Bool(true),
+					Attempts:   Int(DefaultRetryAttempts),
 				},
 				SSL: &SSLConfig{
 					CaCert:     String(""),
@@ -334,9 +335,10 @@ func TestVaultConfig_Finalize(t *testing.T) {
 				Enabled:    Bool(true),
 				RenewToken: Bool(DefaultVaultRenewToken),
 				Retry: &RetryConfig{
-					Backoff:  TimeDuration(DefaultRetryBackoff),
-					Enabled:  Bool(true),
-					Attempts: Int(DefaultRetryAttempts),
+					Backoff:    TimeDuration(DefaultRetryBackoff),
+					MaxBackoff: TimeDuration(DefaultRetryMaxBackoff),
+					Enabled:    Bool(true),
+					Attempts:   Int(DefaultRetryAttempts),
 				},
 				SSL: &SSLConfig{
 					CaCert:     String(""),
@@ -370,9 +372,10 @@ func TestVaultConfig_Finalize(t *testing.T) {
 				Enabled:    Bool(true),
 				RenewToken: Bool(DefaultVaultRenewToken),
 				Retry: &RetryConfig{
-					Backoff:  TimeDuration(DefaultRetryBackoff),
-					Enabled:  Bool(true),
-					Attempts: Int(DefaultRetryAttempts),
+					Backoff:    TimeDuration(DefaultRetryBackoff),
+					MaxBackoff: TimeDuration(DefaultRetryMaxBackoff),
+					Enabled:    Bool(true),
+					Attempts:   Int(DefaultRetryAttempts),
 				},
 				SSL: &SSLConfig{
 					CaCert:     String(""),