express-chaos-middleware/dist/index.js

Put some chaos in your express application

"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
exports.Rules = exports.chaos = void 0;
const debug_1 = __importDefault(require("debug"));
const seedrandom_1 = __importDefault(require("seedrandom"));
const debug = (0, debug_1.default)("express-chaos-middleware");
const Rules = {
    DELAY: delay,
    HTTPERROR: httpError,
    EXCEPTION: exception,
};
exports.Rules = Rules;
/**
 * Generate alphanumeric seed
 * @param length - seed length
 * @returns seed
 */
function generateSeed(length) {
    var result = "";
    var characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    var charactersLength = characters.length;
    for (var i = 0; i < length; i++) {
        result += characters.charAt(Math.floor(Math.random() * charactersLength));
    }
    return result;
}
/**
 * Wait X ms
 * @param ms - waiting time
 */
const wait = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
/**
 * Requests slowdown
 * @param req - express request
 * @param res - express response
 * @param next - express next function
 */
async function delay(req, res, next) {
    const maxDelay = req.options?.maxDelay || 500;
    const pause = Math.floor(req.options.rng() * maxDelay);
    debug(`rulesFunctions.delay - wait ${pause} ms`);
    await wait(pause);
    next();
}
/**
 * Random response error
 * @param req - express request
 * @param res - express response
 */
function httpError(req, res) {
    const errCodes = req.options?.errCodes || [400, 401, 403, 404, 409, 500];
    const code = errCodes[Math.floor(req.options.rng() * errCodes.length)];
    debug(`rulesFunctions.httpError - send ${code} code`);
    res.status(code);
    res.end();
}
/**
 * Throw random exception
 */
function exception() {
    debug(`rulesFunctions.exception - throw exception`);
    throw new Error("BOOM !");
}
/**
 * Randomly throw error and slow response
 * @param options - user options
 * @returns a chaos middleware instance
 */
function chaos(options) {
    const seed = options?.seed || generateSeed(15);
    debug(`current seed ${seed}`);
    const rng = (0, seedrandom_1.default)(seed);
    const chaosOptions = {
        ...options,
        seed,
        rng,
    };
    const probability = chaosOptions?.probability || 10;
    if (!Number.isInteger(probability) || probability < 0 || probability > 100) {
        throw new Error("Invalid probability value");
    }
    const rules = chaosOptions?.rules || [
        Rules.DELAY,
        Rules.HTTPERROR,
        Rules.EXCEPTION,
    ];
    return (req, res, next) => {
        req.options = chaosOptions;
        const rand = Math.floor(chaosOptions.rng() * 100);
        if (rand <= probability) {
            const rule = rules[Math.floor(chaosOptions.rng() * rules.length)];
            return rule(req, res, next);
        }
        return next();
    };
}
exports.chaos = chaos;
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