swaf/src/components/MaintenanceComponent.ts

import config from "config";
import {NextFunction, Request, Response, Router} from "express";

import ApplicationComponent from "../ApplicationComponent.js";
import {ServiceUnavailableHttpError} from "../HttpError.js";

export default class MaintenanceComponent extends ApplicationComponent {
    public async initRoutes(router: Router): Promise<void> {
        router.use((req: Request, res: Response, next: NextFunction) => {
            if (res.headersSent) {
                return next();
            }

            if (!this.getApp().isReady()) {
                res.header({'Retry-After': 60});
                res.locals.refresh_after = 5;
                throw new ServiceUnavailableHttpError(`${config.get('app.name')} is readying up. Please wait a few seconds...`);
            }

            for (const component of this.getApp().getComponents()) {
                if (!component.isReady()) {
                    res.header({'Retry-After': 60});
                    res.locals.refresh_after = 30;
                    throw new ServiceUnavailableHttpError(`${config.get('app.name')} is unavailable due to failure of dependent services.`);
                }
            }

            next();
        });
    }
}