Go Retry Package

Retry Function

The retry function retries a function that returns an error based on the specified RetryOptions until the maximum number of attempts is reached or the function succeeds.

Usage

func retry(fn func() error, ro RetryOptions, retryIf func(error) bool, onRetry func(int, error)) error

• fn is the function to retry. It must return an error.
• ro is a RetryOptions struct that contains the retry configuration.
• retryIf is an optional function that takes an error as input and returns a boolean. If retryIf is not nil and returns false for the error, the retry loop is terminated and the error is returned. If retryIf is nil, all errors are retried.
• onRetry is an optional function that is called after each retry with the attempt number and error as inputs.

type RetryOptions struct {
	DelayFactor         time.Duration
	RandomizationFactor float64
	MaxDelay            time.Duration
	MaxAttempts         int
	Timeout             time.Duration
}

• delayFactor is the base delay for retries.
• randomizationFactor is the amount of jitter to add to the delay.
• maxDelay is the maximum delay between retries.
• maxAttempts is the maximum number of attempts to make.
• timeout is the maximum amount of time to spend retrying.

Functions

func (ro *RetryOptions) Delay(attempt int) time.Duration

This function calculates the delay time for the given retry attempt based on the retry options. It takes an integer representing the current attempt number and returns the delay time as a time.Duration value.

func Retry(ctx context.Context, fn func() error, ro RetryOptions, retryIf func(error) bool, onRetry func(int, error), onTimeout func()) error

This function performs the retries for the given function using the retry options provided. It takes the following arguments:

• ctx is a context.Context that can be used to cancel the retry loop.
• fn is the function to retry. It must return an error.
• ro is a RetryOptions struct that contains the retry configuration.
• retryIf is an optional function that takes an error as input and returns a boolean. If retryIf is not nil and returns false for the error, the retry loop is terminated and the error is returned. If retryIf is nil, all errors are retried.
• onRetry is an optional function that is called after each retry with the attempt number and error as inputs.
• onTimeout is an optional function that is called if the retry loop times out.

Example

package main

import (
    "fmt"
    "math"
    "time"
)

func main() {
	ro := RetryOptions{
		DelayFactor:         200 * time.Millisecond,
		RandomizationFactor: 0.25,
		MaxDelay:            30 * time.Second,
		MaxAttempts:         8,
		Timeout:             5 * time.Minute,
	}
	fn := func() error {
		fmt.Println("Trying...")
		return fmt.Errorf("failed")
	}
	retryIf := func(err error) bool {
		return true
	}
	onRetry := func(attempt int, err error) {
		fmt.Printf("Attempt %d failed: %v\n", attempt, err)
	}
	onTimeout := func() {
		fmt.Println("Retry timed out")
	}
	if err := Retry(context.Background(), fn, ro, retryIf, onRetry, onTimeout); err != nil {
		fmt.Printf("Failed after %d attempts: %v\n", ro.MaxAttempts, err)
	}
}

In this example, the retry function is called with a function that always returns an error. The RetryOptions are set to retry 8 times with a base delay of 200ms and a maximum delay of 30s. The retryIf function always returns true, so all errors are retried. The onRetry function prints the attempt number and error message after each retry. The output of the program is:

Trying...
Attempt 1 failed: failed
Trying...
Attempt 2 failed: failed
Trying...
Attempt 3 failed: failed
Trying...
Attempt 4 failed: failed
Trying...
Attempt 5 failed: failed
Trying...
Attempt 6 failed: failed
Trying...
Attempt 7 failed: failed
Trying...
Attempt 8 failed: failed
Failed after 8 attempts: failed