wait-for-db.ts

/**
 * Copyright (c) 2020 Gitpod GmbH. All rights reserved.
 * Licensed under the GNU Affero General Public License (AGPL).
 * See License.AGPL.txt in the project root for license information.
 */

/**
 * Script that waits for a database to become available
 */
import "reflect-metadata";
import { Config } from "./config";
import * as mysql from "mysql";

const retryPeriod = 5000; // [ms]
const totalAttempts = 30;
const connCfg: mysql.ConnectionConfig = {
    ...new Config().mysqlConfig,
    timeout: retryPeriod,
};

function connectOrReschedule(attempt: number) {
    const con = mysql.createConnection(connCfg);
    try {
        con.connect((err) => {
            if (err) {
                rescheduleConnectionAttempt(attempt, err);
            } else {
                console.log("DB is available");
                con.destroy();
                process.exit(0);
            }
        });
    } catch (err) {
        rescheduleConnectionAttempt(attempt, err);
    }
}

function rescheduleConnectionAttempt(attempt: number, err: Error) {
    if (attempt == totalAttempts) {
        console.log(`Could not connect within ${totalAttempts} attempts. Stopping.`);
        process.exit(1);
    }
    console.log(`Connection attempt ${attempt}/${totalAttempts} failed. Retrying in ${retryPeriod / 1000} seconds.`);
    setTimeout(() => connectOrReschedule(attempt + 1), retryPeriod);
}

connectOrReschedule(0);