istio.io/istio@v0.0.0-20240520182934-d79c90f27776/pkg/backoff/exponential.go (about) 1 // Copyright Istio Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 // Package backoff is a wrapper of `github.com/cenkalti/backoff/v4`. 16 // It is to prevent misuse of `github.com/cenkalti/backoff/v4`, 17 // thus application could fall into dead loop. 18 package backoff 19 20 import ( 21 "context" 22 "fmt" 23 "time" 24 25 "github.com/cenkalti/backoff/v4" 26 ) 27 28 // BackOff is a backoff policy for retrying an operation. 29 type BackOff interface { 30 // NextBackOff returns the duration to wait before retrying the next operation. 31 NextBackOff() time.Duration 32 // Reset to initial state. 33 Reset() 34 // RetryWithContext tries the operation until it does not return error, 35 // or when the context expires, whichever happens first. 36 RetryWithContext(ctx context.Context, operation func() error) error 37 } 38 39 type Option struct { 40 InitialInterval time.Duration 41 MaxInterval time.Duration 42 } 43 44 // ExponentialBackOff is a wrapper of backoff.ExponentialBackOff to override its NextBackOff(). 45 type ExponentialBackOff struct { 46 exponentialBackOff *backoff.ExponentialBackOff 47 } 48 49 // Default values for ExponentialBackOff. 50 const ( 51 defaultInitialInterval = 500 * time.Millisecond 52 defaultMaxInterval = 60 * time.Second 53 ) 54 55 func DefaultOption() Option { 56 return Option{ 57 InitialInterval: defaultInitialInterval, 58 MaxInterval: defaultMaxInterval, 59 } 60 } 61 62 // NewExponentialBackOff creates an istio wrapped ExponentialBackOff. 63 // By default, it never stops. 64 func NewExponentialBackOff(o Option) BackOff { 65 b := ExponentialBackOff{} 66 b.exponentialBackOff = backoff.NewExponentialBackOff() 67 b.exponentialBackOff.InitialInterval = o.InitialInterval 68 b.exponentialBackOff.MaxInterval = o.MaxInterval 69 b.Reset() 70 return b 71 } 72 73 func (b ExponentialBackOff) NextBackOff() time.Duration { 74 duration := b.exponentialBackOff.NextBackOff() 75 // always return maxInterval after it reaches MaxElapsedTime 76 if duration == b.exponentialBackOff.Stop { 77 return b.exponentialBackOff.MaxInterval 78 } 79 return duration 80 } 81 82 func (b ExponentialBackOff) Reset() { 83 b.exponentialBackOff.Reset() 84 } 85 86 // RetryWithContext tries the operation until it does not return error, 87 // or when the context expires, whichever happens first. 88 // o is guaranteed to be run at least once. 89 // RetryWithContext sleeps the goroutine for the duration returned by BackOff after a 90 // failed operation returns. 91 func (b ExponentialBackOff) RetryWithContext(ctx context.Context, operation func() error) error { 92 b.Reset() 93 for { 94 err := operation() 95 if err == nil { 96 return nil 97 } 98 next := b.NextBackOff() 99 select { 100 case <-ctx.Done(): 101 return fmt.Errorf("%v with last error: %v", context.DeadlineExceeded, err) 102 case <-time.After(next): 103 } 104 } 105 }