youtube-maze/lib/retry.mjs

import debug from 'debug';
import { sleep } from './util.mjs';

const log = debug('youtube-maze:retry');

/**
 * An error that is expected to be temporary.
 *
 * If this error is raised, the initial action may be retried after a short
 * period of time, and may eventually succeed.
 */
export class TemporaryError extends Error
{
    constructor(message)
    {
        super(message);
        this.name = this.constructor.name;
        Error.captureStackTrace(this, this.constructor);
    }
}

/**
 * Make an async function retry-able.
 *
 * When the underlying function throws a TemporaryError, the initial
 * call will be repeated, under the limits set below.
 *
 * @param function func Async function to call.
 * @param number retries Allowed number of retries before failing.
 * @param number cooldown Time to wait before retrying (ms).
 * @return function New function that is retryable.
 */
export const retryable = (func, retries = 3, cooldown = 1000) =>
{
    return async (...args) =>
    {
        let remRetries = retries;
        let curCooldown = cooldown;

        while (true)
        {
            try
            {
                const result = await func(...args);
                return result;
            }
            catch (err)
            {
                if (err instanceof TemporaryError && remRetries > 0)
                {
                    log(`\
${func.name}(${args}) failed with error "${err.message}"
Retrying in ${curCooldown} ms (${remRetries} retries remaining)`);

                    await sleep(curCooldown);
                    remRetries -= 1;
                    curCooldown *= 2;
                }
                else
                {
                    throw err;
                }
            }
        }
    };
};

/**
 * Make an async function mutually exclusive.
 *
 * Only one execution of the async function may happen at the same time.
 * In the meantime, other requests are added to a queue.
 *
 * @param function func Async function to call.
 * @param number cooldown Time to wait before two executions.
 */
export const exclusive = (func, cooldown = 2000) =>
{
    let pending = null;

    return async (...args) =>
    {
        if (pending === null)
        {
            pending = func(...args);
        }
        else
        {
            pending = pending
                .then(() => sleep(cooldown))
                .then(() => func(...args));
        }

        return pending;
    };
};