@shopify/react-server/build/esm/metrics/metrics.mjs

Utilities for React server-side rendering

import compose from 'koa-compose';

const MILLIS_PER_SECOND = 1000;
const NANOS_PER_MILLIS = 1e6;
const START_TIME_STATE_KEY = Symbol('startTime');
async function startRequestTiming(ctx, next) {
  ctx.state[START_TIME_STATE_KEY] = process.hrtime();
  await next();
}
async function middleware(ctx, next) {
  try {
    await next();
  } finally {
    const [seconds, nanoseconds] = process.hrtime(ctx.state[START_TIME_STATE_KEY]);
    const ms = seconds * MILLIS_PER_SECOND + nanoseconds / NANOS_PER_MILLIS;
    const requestTime = Math.round(ms);
    const uiMetrics = `ui;request_time=${requestTime}`;
    ctx.set('Server-Timing', uiMetrics);
  }
}
const metricsMiddleware = compose([startRequestTiming, middleware]);

export { metricsMiddleware };