backoff

Documentation

Overview

Package backoff computes retry delays.

It exists as its own package so that the delay arithmetic — the part that is easy to get subtly wrong and easy to test in isolation — is not tangled up with the LDAP error classification that decides whether to retry at all.

Index

• type Policy
  • func (p Policy) Delay(n int) time.Duration

Types

type Policy

type Policy struct {
	// Base is the delay before the first retry. Subsequent delays grow
	// from it by Multiplier.
	Base time.Duration

	// Max caps a single delay, however many attempts have failed.
	Max time.Duration

	// Multiplier is the growth factor between attempts. Values below 1
	// are treated as 1, which turns the policy into a constant delay.
	Multiplier float64
}

Policy describes a capped exponential backoff with full jitter.

Full jitter, rather than the exponential delay itself or the delay plus a small random nudge, is what actually decorrelates a fleet of clients that all lost their directory at the same instant: every waiter picks uniformly from [0, delay), so the retries spread across the window instead of arriving together at the end of it.

func (Policy) Delay

func (p Policy) Delay(n int) time.Duration

Delay returns how long to wait before attempt number n, where n counts from 1 for the first retry. A non-positive n returns zero.

The caller is expected to sample once per retry and to select on its context while waiting; Delay does no waiting of its own and touches no clock, which is why it is trivially testable.