server-timing

This module adds Server-Timing to HTTP response headers. An example is available here. To see the Server-Timing headers in action, open the network tab in your browser's developer tools when viewing the example.

This module can be used as an Express middleware or with Node.js's basic HTTP module.

Install

$ npm install server-timing -S

Usage

constexpress=require('express');constserverTiming=require('server-timing');constapp=express();app.use(serverTiming());app.use((req,res,next)=>{res.startTime('file','File IO metric');setTimeout(()=>{res.endTime('file');},100);next();});app.use((req,res,next)=>{// Example: A timer started but not explicitly ended (if autoEnd is true).res.startTime('test','forget to call endTime');next();});app.use((req,res,next)=>{// Server-Timing headers expect timing values in milliseconds. Ensure all metrics are provided in milliseconds. See issue #9 (https://github.com/yosuke-furukawa/server-timing/issues/9) for more context.res.setMetric('db',100.0,'Database metric');res.setMetric('api',200.0,'HTTP/API metric');res.setMetric('cache',300.0,'cache metric');next();});app.use((req,res,next)=>{res.send('hello');});

Conditionally enabled

constexpress=require('express');constserverTiming=require('server-timing');constapp=express();app.use(serverTiming({// Example: Only send Server-Timing headers if a 'debug' query parameter is true.enabled: (req,res)=>req.query.debug==='true'}));

API

constructor(options)

• options.name: string, default 'total'. The name for the primary timing metric, often representing the total request processing time.
• options.description: string, default 'Total Response Time'. A human-readable description for the primary timing metric.
• options.total: boolean, default true. If true, automatically includes a metric for the total response time.
• options.enabled: boolean | function, default true. Controls whether Server-Timing headers are added. If a function is provided, it's called with request and response objects and must return a boolean to determine if headers should be sent for the current request.
• options.autoEnd: boolean, default true. If true, endTime() is automatically called for any timers that were started with startTime() but not explicitly ended before the response finishes.
• options.precision: number, default +Infinity. Specifies the number of decimal places to use for timing values in the Server-Timing header.

Example Result

The Server-Timing headers will appear in the browser's developer tools, typically in the Network tab when inspecting a response. Here's an example of how it might look: