express-server-timing-middleware
Express middleware to measure application performance and add Server-Timing headers to response
Motivation
- To get more control over server side performance on the level of logging and monitoring.
- To have ability to conditionally add Server-Timing headers based on request parameters
- To be able to extract Server-Timing metrics for further logging
Usage
Add serverTiming middleware to your app router or subrouter
import express from 'express';
import { createServerTimingMiddleware } from 'express-server-timing-middleware';
// example controllers
import { createRenderController } from './controllers/app-render.controller';
import { shouldWriteDebugHeaders } from './utils';
const app = express();
app.use([
serverTiming({
// define if headers should be included into response.
// Use boolean value or a function that should return true to include Server-Timing header
writeHeaders: process.env.NODE_ENV !== 'production' || shouldWriteDebugHeaders,
}),
// any other middlewares
]);
app.get(/.*/, createRenderController());
app.listen(APP_PORT, (error) => {
if (error) {
} else {
console.log(`Express app started on port ${APP_PORT}`);
}
});// utils.ts example
import type { Request } from 'express';
export const extractToken = (req: Request): string | undefined => {
return req.header('my-secret-token');
};
export const checkTokenPermission = (token: string): boolean => {
const parsedToken = decodeJWT(token);
if (parsedToken === null) {
return false;
}
return parsedToken.scopes.includes('my-secret-permission');
};
export const shouldWriteDebugHeaders = (req: Request) => {
const token = extractTokenAndCheckPermissions(req);
if (!token) {
return false;
}
const hasValidPermissions = checkTokenPermission(token);
return hasValidPermissions;
};Use serverTiming tracker withing your controllers or middlewares
// app-render.controller.ts example
import type { Request, Response, NextFunction } from 'express';
export const createRenderController =
() => async (req: Request, res: Response, _next: NextFunction) => {
try {
// any tracking calls that were are not explicitly ended
// will be fulfilled with final values right before sending response
req.serverTiming.start('Request started', 'Optional description');
req.serverTiming.start('render', 'render-application');
const applicationResponse = await getSomeApplicationResponse();
req.serverTiming.end('render');
// do some other stuff
res.send(applicationResponse);
} catch (error) {
req.log.error(error, 'Application rendering failed');
next(error);
}
};Use serverTiming tracker withing you middleware to collect all completed metrics
// server-timing-logger.middleware.ts example
import type { Request, Response, NextFunction } from 'express';
import type { ExpressServerTimingMetric } from 'express-server-timing-middleware';
export const serverTimingLogger = () => (req: Request, res: Response, next: NextFunction) => {
try {
const serverTimings: ExpressServerTimingMetric[] = req.serverTiming.getSnapshot();
// use any of loggers defined on request/app level to log data
req.log.info(serverTimings, 'server timings');
next();
} catch (error) {
req.log.error(error, 'Server timing logging failed.');
next();
}
};