67 lines
2.1 KiB
Go
67 lines
2.1 KiB
Go
// Package backoff provides stateless methods of calculating durations based on
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// a number of attempts made.
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package backoff
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import (
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"math"
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"time"
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)
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// Algorithm defines a function that calculates a time.Duration based on
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// the given retry attempt number.
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type Algorithm func(attempt uint) time.Duration
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// Incremental creates a Algorithm that increments the initial duration
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// by the given increment for each attempt.
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func Incremental(initial, increment time.Duration) Algorithm {
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return func(attempt uint) time.Duration {
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return initial + (increment * time.Duration(attempt))
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}
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}
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// Linear creates a Algorithm that linearly multiplies the factor
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// duration by the attempt number for each attempt.
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func Linear(factor time.Duration) Algorithm {
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return func(attempt uint) time.Duration {
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return factor * time.Duration(attempt)
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}
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}
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// Exponential creates a Algorithm that multiplies the factor duration by
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// an exponentially increasing factor for each attempt, where the factor is
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// calculated as the given base raised to the attempt number.
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func Exponential(factor time.Duration, base float64) Algorithm {
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return func(attempt uint) time.Duration {
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return factor * time.Duration(math.Pow(base, float64(attempt)))
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}
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}
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// BinaryExponential creates a Algorithm that multiplies the factor
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// duration by an exponentially increasing factor for each attempt, where the
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// factor is calculated as `2` raised to the attempt number (2^attempt).
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func BinaryExponential(factor time.Duration) Algorithm {
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return Exponential(factor, 2)
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}
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// Fibonacci creates a Algorithm that multiplies the factor duration by
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// an increasing factor for each attempt, where the factor is the Nth number in
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// the Fibonacci sequence.
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func Fibonacci(factor time.Duration) Algorithm {
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return func(attempt uint) time.Duration {
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return factor * time.Duration(fibonacciNumber(attempt))
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}
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}
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// fibonacciNumber calculates the Fibonacci sequence number for the given
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// sequence position.
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func fibonacciNumber(n uint) uint {
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if n == 0 {
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return 0
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}
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var a, b uint = 0, 1
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for i := uint(1); i < n; i++ {
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a, b = b, a+b
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}
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return b
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}
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