adc23d5f96
git-subtree-dir: x git-subtree-mainline: 7d05a6ee8f44b314fa697a427439e5fa4d78c3d7 git-subtree-split: a10a11b9d371f36b7c3510da32a1d70b74e27bd1
59 lines
1.4 KiB
Go
59 lines
1.4 KiB
Go
package backoff
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import (
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"context"
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"errors"
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"iter"
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"math/rand"
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"time"
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)
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// Errors
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var (
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// ErrMaxAttempts is not used by backoff but is available for use by
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// callers that want to signal that a maximum number of retries has
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// been exceeded. This should eliminate the need for callers to invent
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// their own error.
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ErrMaxAttempts = errors.New("max retries exceeded")
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)
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// Upto implements a backoff strategy that yields nil errors until the
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// context is canceled, the maxRetries is exceeded, or yield returns false.
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//
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// The backoff strategy is a simple exponential backoff with a maximum
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// backoff of maxBackoff. The backoff is randomized between 0.5-1.5 times
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// the current backoff, in order to prevent accidental "thundering herd"
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// problems.
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func Upto(ctx context.Context, maxBackoff time.Duration) iter.Seq2[int, error] {
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var n int
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return func(yield func(int, error) bool) {
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for {
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if ctx.Err() != nil {
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yield(n, ctx.Err())
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return
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}
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n++
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// n^2 backoff timer is a little smoother than the
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// common choice of 2^n.
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d := time.Duration(n*n) * 10 * time.Millisecond
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if d > maxBackoff {
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d = maxBackoff
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}
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// Randomize the delay between 0.5-1.5 x msec, in order
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// to prevent accidental "thundering herd" problems.
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d = time.Duration(float64(d) * (rand.Float64() + 0.5))
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t := time.NewTimer(d)
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select {
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case <-ctx.Done():
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t.Stop()
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case <-t.C:
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if !yield(n, nil) {
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return
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}
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}
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}
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}
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}
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