express-middleware-server-timing

Automagic expressjs middleware performance monitoring.

There are many server-timing libraries out there for expressjs, but I couldn't find any that provided any out-of-the-box value.

Installation

``sh
npm install --save express-middleware-server-timing
`

Usage

`js
const app = express()

// any time before app.listen(...)
require('express-middleware-server-timing')(app, [options])
`

The following table describes the properties of the options object.

| Property | Description | Type | Default |
|---------------|-----------------------------------------|--------|-------------|
| name | name of the server timing metric | String | 'mw' |
| description | description of the server timing metric | String | undefined |
| disabled | set true if you want to disable | Boolean| false |

A server-timing entry named (with optional description of ) will be generated for every request that passes through express.

Manual instrumentation

$3

To create a server-timing entry reporting the duration between two check points of the same response, try:

`javascript

app.get(path, function (req, res, next) {
res.serverTimingStart('foo', 'bar')

// some time later, maybe in different middleware handler
res.serverTimingStop('foo')

// ...
})
`
A header like this will be written to the response:
`
Server-Timing: foo; dur=[time in ms]; desc="bar"
`

$3


To create a server-timing entry reporting the duration it took to execute a syncronous method, try:
`javascript
app.get(path, function (req, res, next) {
const result = res.serverTimingSync(function() {
// slow syncronous code here
}, 'slowMethod1', 'sometimes this method is slow')

// ...
})
`

A header like this will be written to the response:
`
Server-Timing: slowMethod1; dur=[time in ms]; desc="sometimes this method is slow"
`

Browser Collection

For browsers that suport server-timing (Chrome 65+, Opera 52+), the entries can be accessed like this:
`javascript
['navigation', 'resource']
.forEach(function(entryType) {
performance.getEntriesByType(entryType).forEach(function({name: url, serverTiming}) {
serverTiming.forEach(function({name, duration, description}) {
console.info('expressjs middleware =',
JSON.stringify({url, entryType, name, duration, description}, null, 2))
})
})
})
`

Conditionally disable (example: based on environment)

`javascript
require('express-middleware-server-timing')(app, {
disabled: process.env.NODE_ENV === 'production'
})
``

License

MIT