1// Package backoff implements backoff algorithms for retrying operations. 2// 3// Use Retry function for retrying operations that may fail. 4// If Retry does not meet your needs, 5// copy/paste the function into your project and modify as you wish. 6// 7// There is also Ticker type similar to time.Ticker. 8// You can use it if you need to work with channels. 9// 10// See Examples section below for usage examples. 11package backoff 12 13import "time" 14 15// BackOff is a backoff policy for retrying an operation. 16type BackOff interface { 17 // NextBackOff returns the duration to wait before retrying the operation, 18 // or backoff. Stop to indicate that no more retries should be made. 19 // 20 // Example usage: 21 // 22 // duration := backoff.NextBackOff(); 23 // if (duration == backoff.Stop) { 24 // // Do not retry operation. 25 // } else { 26 // // Sleep for duration and retry operation. 27 // } 28 // 29 NextBackOff() time.Duration 30 31 // Reset to initial state. 32 Reset() 33} 34 35// Stop indicates that no more retries should be made for use in NextBackOff(). 36const Stop time.Duration = -1 37 38// ZeroBackOff is a fixed backoff policy whose backoff time is always zero, 39// meaning that the operation is retried immediately without waiting, indefinitely. 40type ZeroBackOff struct{} 41 42func (b *ZeroBackOff) Reset() {} 43 44func (b *ZeroBackOff) NextBackOff() time.Duration { return 0 } 45 46// StopBackOff is a fixed backoff policy that always returns backoff.Stop for 47// NextBackOff(), meaning that the operation should never be retried. 48type StopBackOff struct{} 49 50func (b *StopBackOff) Reset() {} 51 52func (b *StopBackOff) NextBackOff() time.Duration { return Stop } 53 54// ConstantBackOff is a backoff policy that always returns the same backoff delay. 55// This is in contrast to an exponential backoff policy, 56// which returns a delay that grows longer as you call NextBackOff() over and over again. 57type ConstantBackOff struct { 58 Interval time.Duration 59} 60 61func (b *ConstantBackOff) Reset() {} 62func (b *ConstantBackOff) NextBackOff() time.Duration { return b.Interval } 63 64func NewConstantBackOff(d time.Duration) *ConstantBackOff { 65 return &ConstantBackOff{Interval: d} 66} 67