Retry

Retry is a golang pure package implements the retry-pattern to retry failures until certain attempts in certain time.

Installation

At first you need to download the library using go get

$ go get -u github.com/morilog/retry

Or just use it on your package by importing this:

import "github.com/morilog/retry"

And download it with go mod

$ go mod tidy

Quick Start

Assume you have a function that calls an external api:

func getSomeExternalData(url string) error {
    // your business logic goes here
}

It might be failed during network errors or any other external errors. With retry you can retry your logic until maximum number of attempts exceeded.

package main

import "github.com/morilog/retry"

func main() {
    ctx := context.Background()

    // As default
    // It retries 10 times with increased 100ms delay
    err := retry.Retry(ctx, func() error {
        return getSomeExternalData("https://example.com")
    }, retry.Delay(time.Second))

    if err != nil {
        log.Fatal(err)
    }
}

Options

retry.Delay(delay time.Duration)

To set minimum delay duration between each retry.

Default: 100ms

retry.DelayFactor(factor int)

To set number that multiplies to delay to increase delay time by increasing attempts. The delay for each retry calculated by this formula:

    AttemptDelay = Attempt * DelayFactor * Delay

Default: 1

retry.MaxAttempts(attempts uint8)

Sets maximum number of attempts to handle the operation

Default: 10

retry.StopRetryIf(fn StopRetryIfFunc)

Sometimes you need to cancel the retry mechanism when your operation returns some specific error. To achieve to this purpose, You can use this option.

Default: <not set>

For example i stop the retry when an SomeError occurred:

err := retry.Retry(ctx, func() error {
    return getSomeExternalData("https://example.com")
},
    retry.Delay(time.Second),
    retry.StopRetryIf(func(ctx context.Context, err error) bool {
        if _, ok := err.(*SomeError); ok {
            return true
        }

        return false
    }),
)

if err != nil {
    log.Fatal(err)
}

retry.OnRetry(fn OnRetryFunc)

Sometimes you need to know retry is on which attempt to do something like logging

Default: <not set>

For example:

err := retry.Retry(ctx, func() error {
    return getSomeExternalData("https://example.com")
},
    retry.Delay(time.Second),
    retry.StopRetryIf(func(ctx context.Context, attempt int) error {
        logrus.Printf("The function retries for %d times.\n", attempt)
        return nil
    }),
)

if err != nil {
    log.Fatal(err)
}