Aleksey Shakhmatov
43d3ecfba1
Gate the retry decision on body rewindability: an idempotent request whose body cannot be replayed (no GetBody) is now returned as-is instead of looping with an empty body or surfacing a stale, already-drained response. Guard ExponentialBackoff against rand.Int64N panicking when delay/2 rounds to zero. Use internal/clock for inter-attempt delays so retry timing is consistent with the rest of the codebase and testable without real sleeps.
68 lines
1.5 KiB
Go
68 lines
1.5 KiB
Go
package retry
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import (
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"math/rand/v2"
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"time"
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)
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// Backoff computes the delay before the next retry attempt.
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type Backoff interface {
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// Delay returns the wait duration for the given attempt number (zero-based).
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Delay(attempt int) time.Duration
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}
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// ExponentialBackoff returns a Backoff that doubles the delay on each attempt.
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// The delay is calculated as base * 2^attempt, capped at max. When withJitter
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// is true, a random duration in [0, delay*0.5) is added.
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func ExponentialBackoff(base, max time.Duration, withJitter bool) Backoff {
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return &exponentialBackoff{
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base: base,
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max: max,
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withJitter: withJitter,
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}
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}
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// ConstantBackoff returns a Backoff that always returns the same delay.
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func ConstantBackoff(d time.Duration) Backoff {
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return constantBackoff{delay: d}
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}
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type exponentialBackoff struct {
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base time.Duration
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max time.Duration
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withJitter bool
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}
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func (b *exponentialBackoff) Delay(attempt int) time.Duration {
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delay := b.base
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for range attempt {
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delay *= 2
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if delay >= b.max {
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delay = b.max
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break
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}
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}
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if b.withJitter {
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// Guard against rand.Int64N panicking on a non-positive argument when
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// delay is small enough that delay/2 rounds to zero.
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if half := int64(delay / 2); half > 0 {
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delay += time.Duration(rand.Int64N(half))
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}
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}
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if delay > b.max {
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delay = b.max
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}
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return delay
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}
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type constantBackoff struct {
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delay time.Duration
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}
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func (b constantBackoff) Delay(_ int) time.Duration {
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return b.delay
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}
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