@fortify-ts/retry

Retry pattern with configurable backoff strategies for the Fortify-TS resilience library.

Installation

npm install @fortify-ts/retry
# or
pnpm add @fortify-ts/retry

Features

• Backoff Policies: Exponential, linear, and constant
• Configurable Delays: Initial delay, max delay, multiplier
• Jitter Support: Prevent thundering herd
• Custom Predicates: isRetryable callback
• Retry Notifications: onRetry callback

Usage

Basic Usage

import { Retry } from '@fortify-ts/retry';

const retry = new Retry<Response>({
  maxAttempts: 3,
  initialDelay: 100,
});

const result = await retry.execute(async (signal) => {
  return fetch('/api/data', { signal });
});

Configuration Options

const retry = new Retry<Response>({
  // Maximum attempts (including initial)
  maxAttempts: 5,

  // Initial delay between retries (ms)
  initialDelay: 100,

  // Maximum delay between retries (ms)
  maxDelay: 10000,

  // Backoff policy
  backoffPolicy: 'exponential', // 'exponential' | 'linear' | 'constant'

  // Delay multiplier for exponential/linear
  multiplier: 2.0,

  // Add random jitter to delays
  jitter: true,

  // Custom retry condition
  isRetryable: (error) => {
    if (error instanceof NetworkError) return true;
    if (error instanceof ValidationError) return false;
    return true;
  },

  // Retry notification
  onRetry: (error, attempt) => {
    console.log(`Retry ${attempt}: ${error.message}`);
  },

  // Optional logger
  logger: myLogger,
});

Backoff Policies

// Exponential: delay = initialDelay * (multiplier ^ attempt)
// 100ms → 200ms → 400ms → 800ms → 1600ms
const exponential = new Retry({ backoffPolicy: 'exponential' });

// Linear: delay = initialDelay * (multiplier * attempt)
// 100ms → 200ms → 300ms → 400ms → 500ms
const linear = new Retry({ backoffPolicy: 'linear' });

// Constant: delay = initialDelay
// 100ms → 100ms → 100ms → 100ms → 100ms
const constant = new Retry({ backoffPolicy: 'constant' });

Marking Errors as Retryable

import { asRetryable, asNonRetryable } from '@fortify-ts/core';

// In your code, mark errors explicitly
if (isTemporary) {
  throw asRetryable(new Error('Temporary failure'));
} else {
  throw asNonRetryable(new Error('Permanent failure'));
}

Configuration Reference

| Option | Type | Default | Description | |--------|------|---------|-------------| | maxAttempts | number | 3 | Maximum attempts | | initialDelay | number | 100 | Initial delay (ms) | | maxDelay | number | - | Maximum delay (ms) | | backoffPolicy | string | 'exponential' | Backoff policy | | multiplier | number | 2.0 | Delay multiplier | | jitter | boolean | false | Add jitter | | isRetryable | function | - | Custom retry check | | onRetry | function | - | Retry callback | | logger | FortifyLogger | - | Optional logger |

License

MIT