go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/retry/exponential.go (about)

     1  // Copyright 2015 The LUCI 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 retry
    16  
    17  import (
    18  	"context"
    19  	"time"
    20  )
    21  
    22  // ExponentialBackoff is an Iterator implementation that implements exponential
    23  // backoff retry.
    24  type ExponentialBackoff struct {
    25  	Limited
    26  
    27  	// Multiplier is the exponential growth multiplier. If < 1, a default of 2
    28  	// will be used.
    29  	Multiplier float64
    30  	// MaxDelay is the maximum duration. If <= zero, no maximum will be enforced.
    31  	MaxDelay time.Duration
    32  }
    33  
    34  // Next implements Iterator.
    35  func (b *ExponentialBackoff) Next(ctx context.Context, err error) time.Duration {
    36  	// Get Limited base delay.
    37  	delay := b.Limited.Next(ctx, err)
    38  	if delay == Stop {
    39  		return Stop
    40  	}
    41  
    42  	// Bound our delay.
    43  	if b.MaxDelay > 0 && b.MaxDelay < delay {
    44  		delay = b.MaxDelay
    45  	} else {
    46  		// Calculate the next delay exponentially.
    47  		multiplier := b.Multiplier
    48  		if multiplier < 1 {
    49  			multiplier = 2
    50  		}
    51  		b.Delay = time.Duration(float64(b.Delay) * multiplier)
    52  	}
    53  	return delay
    54  }