waitForIt.ts

import { exponential } from 'backoff'

/**
 * @module
 *
 * This module contains the function that retries a given function.
 */

/**
 * Retries the given function using a backoff algorithm.
 * It times out after 27.75 sec by default (9 attempts)
 *
 * @example Wait for a tenant to be available
 * ```ts
 * import { waitForIt } from "@nrfcloud/wait-for-it";
 *
 * const tenant = await wait_for_it<Tenant>(() =>
 *   repo.getByUUID(
 *     e.aggregateUUID,
 *   )
 * );
 * ```
 */
export const waitForIt = <A>(
	fn: () => Promise<A>,
	retryNumber: number = 9,
): Promise<A> =>
	new Promise((resolve, reject) => {
		const b = exponential({
			randomisationFactor: 0,
			initialDelay: 250,
			maxDelay: 5000,
		})
		let lastErr: Error
		b.failAfter(retryNumber)
		b.on('ready', async () => {
			try {
				const res = await fn()
				return resolve(res)
			} catch (e) {
				lastErr = e as Error
			}
			b.backoff()
		})
		b.on('fail', () => {
			reject(lastErr)
		})
		b.backoff()
	})