backoff

Documentation

Index

• Constants
• Variables
• func Retry(o Operation, b BackOff) error
• func RetryNotify(operation Operation, b BackOff, notify Notify) error
• type BackOff
  • func WithMaxRetries(b BackOff, max uint64) BackOff
• type BackOffContext
  • func WithContext(b BackOff, ctx context.Context) BackOffContext
• type Clock
• type ConstantBackOff
  • func NewConstantBackOff(d time.Duration) *ConstantBackOff
  • func (b *ConstantBackOff) NextBackOff() time.Duration
  • func (b *ConstantBackOff) Reset()
• type ExponentialBackOff
  • func NewExponentialBackOff() *ExponentialBackOff
  • func (b *ExponentialBackOff) GetElapsedTime() time.Duration
  • func (b *ExponentialBackOff) NextBackOff() time.Duration
  • func (b *ExponentialBackOff) Reset()
• type Notify
• type Operation
• type PermanentError
  • func Permanent(err error) *PermanentError
  • func (e *PermanentError) Error() string
• type StopBackOff
  • func (b *StopBackOff) NextBackOff() time.Duration
  • func (b *StopBackOff) Reset()
• type Ticker
  • func NewTicker(b BackOff) *Ticker
  • func (t *Ticker) Stop()
• type ZeroBackOff
  • func (b *ZeroBackOff) NextBackOff() time.Duration
  • func (b *ZeroBackOff) Reset()

Constants

const (
	DefaultInitialInterval     = 500 * time.Millisecond
	DefaultRandomizationFactor = 0.5
	DefaultMultiplier          = 1.5
	DefaultMaxInterval         = 60 * time.Second
	DefaultMaxElapsedTime      = 15 * time.Minute
)

Default values for ExponentialBackOff.

const Stop time.Duration = -1

Stop indicates that no more retries should be made for use in NextBackOff().

Variables

var SystemClock = systemClock{}

SystemClock implements Clock interface that uses time.Now().

Functions

func Retry

func Retry(o Operation, b BackOff) error

Retry the operation o until it does not return error or BackOff stops. o is guaranteed to be run at least once. It is the caller's responsibility to reset b after Retry returns.

If o returns a *PermanentError, the operation is not retried, and the wrapped error is returned.

Retry sleeps the goroutine for the duration returned by BackOff after a failed operation returns.

func RetryNotify

func RetryNotify(operation Operation, b BackOff, notify Notify) error

RetryNotify calls notify function with the error and wait duration for each failed attempt before sleep.

Types

type BackOff

type BackOff interface {
	// returns duration
	NextBackOff() time.Duration

	// Reset to initial state.
	Reset()
}

BackOff is a backoff policy for retrying an operation.

func WithMaxRetries

func WithMaxRetries(b BackOff, max uint64) BackOff

WithMaxRetries creates a wrapper around another BackOff, which will return Stop if NextBackOff() has been called too many times since the last time Reset() was called Note: Implementation is not thread-safe.

type BackOffContext

type BackOffContext interface {
	BackOff
	Context() context.Context
}

BackOffContext is a backoff policy that stops retrying after the context is canceled.

func WithContext

func WithContext(b BackOff, ctx context.Context) BackOffContext

WithContext returns a BackOffContext with context ctx

ctx must not be nil

type Clock

type Clock interface {
	Now() time.Time
}

Clock is an interface that returns current time for BackOff.

type ConstantBackOff

type ConstantBackOff struct {
	Interval time.Duration
}

ConstantBackOff is a backoff policy that always returns the same backoff delay. This is in contrast to an exponential backoff policy, which returns a delay that grows longer as you call NextBackOff() over and over again.

func NewConstantBackOff

func NewConstantBackOff(d time.Duration) *ConstantBackOff

func (*ConstantBackOff) NextBackOff

func (b *ConstantBackOff) NextBackOff() time.Duration

func (*ConstantBackOff) Reset

func (b *ConstantBackOff) Reset()

type ExponentialBackOff

type ExponentialBackOff struct {
	InitialInterval     time.Duration
	RandomizationFactor float64
	Multiplier          float64
	MaxInterval         time.Duration
	// After MaxElapsedTime the ExponentialBackOff stops.
	// It never stops if MaxElapsedTime == 0.
	MaxElapsedTime time.Duration
	Clock          Clock
	// contains filtered or unexported fields
}

func NewExponentialBackOff

func NewExponentialBackOff() *ExponentialBackOff

NewExponentialBackOff creates an instance of ExponentialBackOff using default values.

func (*ExponentialBackOff) GetElapsedTime

func (b *ExponentialBackOff) GetElapsedTime() time.Duration

GetElapsedTime returns the elapsed time since an ExponentialBackOff instance is created and is reset when Reset() is called.

The elapsed time is computed using time.Now().UnixNano(). It is safe to call even while the backoff policy is used by a running ticker.

func (*ExponentialBackOff) NextBackOff

func (b *ExponentialBackOff) NextBackOff() time.Duration

NextBackOff calculates the next backoff interval using the formula:

Randomized interval = RetryInterval +/- (RandomizationFactor * RetryInterval)

func (*ExponentialBackOff) Reset

func (b *ExponentialBackOff) Reset()

Reset the interval back to the initial retry interval and restarts the timer.

type Notify

type Notify func(error, time.Duration)

Notify is a notify-on-error function. It receives an operation error and backoff delay if the operation failed (with an error).

NOTE that if the backoff policy stated to stop retrying, the notify function isn't called.

type Operation

type Operation func() error

An Operation is executing by Retry() or RetryNotify(). The operation will be retried using a backoff policy if it returns an error.

type PermanentError

type PermanentError struct {
	Err error
}

PermanentError signals that the operation should not be retried.

func Permanent

func Permanent(err error) *PermanentError

Permanent wraps the given err in a *PermanentError.

func (*PermanentError) Error

func (e *PermanentError) Error() string

type StopBackOff

type StopBackOff struct{}

StopBackOff is a fixed backoff policy that always returns backoff.Stop for NextBackOff(), meaning that the operation should never be retried.

func (*StopBackOff) NextBackOff

func (b *StopBackOff) NextBackOff() time.Duration

func (*StopBackOff) Reset

func (b *StopBackOff) Reset()

type Ticker

type Ticker struct {
	C <-chan time.Time
	// contains filtered or unexported fields
}

Ticker holds a channel that delivers `ticks' of a clock at times reported by a BackOff.

Ticks will continue to arrive when the previous operation is still running, so operations that take a while to fail could run in quick succession.

func NewTicker

func NewTicker(b BackOff) *Ticker

NewTicker returns a new Ticker containing a channel that will send the time at times specified by the BackOff argument. Ticker is guaranteed to tick at least once. The channel is closed when Stop method is called or BackOff stops. It is not safe to manipulate the provided backoff policy (notably calling NextBackOff or Reset) while the ticker is running.

func (*Ticker) Stop

func (t *Ticker) Stop()

Stop turns off a ticker. After Stop, no more ticks will be sent.

type ZeroBackOff

type ZeroBackOff struct{}

ZeroBackOff is a fixed backoff policy whose backoff time is always zero, meaning that the operation is retried immediately without waiting, indefinitely.

func (*ZeroBackOff) NextBackOff

func (b *ZeroBackOff) NextBackOff() time.Duration

func (*ZeroBackOff) Reset

func (b *ZeroBackOff) Reset()