Prometheus metrics plugin for Elysia framework
npm install elysia-prometheusA lightweight plugin for Elysia that exposes HTTP metrics for Prometheus using prom-client. Automatically tracks request count, duration, method, status code, and more — with support for custom labels.
- ✅ Exposes /metrics endpoint (configurable)
- 📊 Collects request duration and total request count
- 🏷 Supports static and dynamic labels
- 🧠 Route normalization for consistent metric names
- 🪝 Integrates with derive and onAfterHandle lifecycle hooks
``bash`
bun install elysia-prometheus
`ts
import { sleep } from 'bun'
import { Elysia, error } from 'elysia'
import prometheusPlugin from 'elysia-prometheus'
const app = new Elysia()
.use(
prometheusPlugin({
metricsPath: '/metrics',
staticLabels: { service: 'my-app' },
dynamicLabels: {
userAgent: (ctx) =>
ctx.request.headers.get('user-agent') ?? 'unknown'
}
})
)
.get('/', () => 'GET /')
.post('/', () => 'POST /')
.get('/delay', () => {
sleep(1000)
return 'GET /delay'
})
.get('/error/:code', ({ params }) => {
return error(Number.parseInt(params.code))
})
.listen(3000)
`
- http_requests_total — Counter of total HTTP requests
- http_request_duration_seconds — Histogram of request durations
- method – HTTP method (GET, POST, etc.)
- path – Normalized route path (e.g., /users/:id)
- status – HTTP status code (200, 404, etc.)
- staticLabels: Adds the same label value for every request
- dynamicLabels: Functions that extract values from each request context
| Option | Type | Default | Description |
| ----------------- | ------------------------------------------ | ---------------------------------- | -------------------------------------------------------------------------------- |
| metricsPath | string | "/metrics" | URL path to expose metrics |durationBuckets
| | number[] | [0.003, 0.03, 0.1, 0.3, 1.5, 10] | Histogram buckets for request duration |staticLabels
| | Record | {} | Static labels added to all metrics |dynamicLabels
| | Record | {} | Dynamic labels based on request context |useRoutePath
| | boolean | true | Use route pattern instead of raw URL (e.g. /users/:id instead of /users/123) |
> ⚠️ Label names method, path, and status are reserved and cannot be overridden.
The plugin automatically normalizes paths like:
`
/users/123/orders/456 → /users/:id/orders/:id
This prevents metric explosion from unique IDs in URLs.
MIT
If you want to add or improve the library or its documentation, make a pull request to this repository. Please use bun and format js and ts code with prettier to make everything look nice.