Prometheus Node.js Middleware

0.0.3 verified Thu Apr 23 auth: no javascript abandoned

Menoetius is a Node.js middleware designed to automatically instrument web applications and expose Prometheus-compatible metrics. It enables developers to easily gather response duration metrics (summary and histogram types) and fundamental Node.js system metrics, all accessible via a configurable `/metrics` endpoint. The library supports integration with popular HTTP frameworks like `http`, `express`, `hapi`, and `restify`. However, the package is currently at a very early version (0.0.3), was likely published many years ago, and appears to be abandoned, with no discernible updates or active development. It relies on `prom-client` for metric collection, which has evolved significantly since Menoetius's last release. Due to its unmaintained status, it may lack compatibility with modern Node.js versions and up-to-date Prometheus client best practices, making it unsuitable for new projects.

Common errors

error TypeError: menoetius.instrument is not a function ↓

cause The `menoetius` module was either not properly imported, or the package is corrupted/incomplete.

fix

Ensure npm install menoetius ran successfully and const menoetius = require('menoetius'); is correctly placed. Given the package's age, consider if it's installed alongside incompatible Node.js or dependency versions.

error Error: Cannot find module 'menoetius' ↓

cause The `menoetius` package is not installed in your project's `node_modules` directory.

fix

Run npm install --save menoetius to add the package to your project dependencies.

error Error: The 'request' module is not found. Menoetius requires 'request' as a dependency. ↓

cause Menoetius depends on the `request` package, which is now deprecated and might cause issues with newer Node.js versions or package managers.

fix

While request is likely a transitive dependency, the ultimate fix for Menoetius's issues is to migrate to a modern, maintained Prometheus client solution.

Warnings

breaking The Menoetius package (version 0.0.3) is extremely old and has been abandoned for several years. It is highly unlikely to be compatible with modern Node.js versions (e.g., Node.js 14+), newer Express.js versions, or the latest `prom-client` APIs. Expect significant breaking changes and runtime errors. ↓

fix Avoid using Menoetius for new projects. For existing applications, consider migrating to a actively maintained Prometheus client library like `prom-client` directly or another up-to-date middleware.

gotcha Menoetius uses an outdated approach to normalize request paths for labels (e.g., `/users/freddie` becomes `/users/`). While this prevents high cardinality, it might mask granular performance issues at specific user or resource endpoints. Modern Prometheus clients often allow more configurable path labeling strategies. ↓

fix Be aware of the path aggregation and ensure it meets your monitoring requirements. If granular path metrics are critical, this library is not suitable.

breaking Due to its abandonment, Menoetius will not receive security updates. Running it in production could expose your application to known or unknown vulnerabilities related to its dependencies or its own code. ↓

fix Upgrade to a actively maintained Prometheus client library and middleware (e.g., `prom-client` directly) to ensure ongoing security patches and compliance.

Install

npm install menoetius

yarn add menoetius

pnpm add menoetius

Imports

menoetius
wrong
```
import menoetius from 'menoetius';
```
correct
```
const menoetius = require('menoetius');
```
Menoetius was released as a CommonJS module (Node.js >=4.0.0). Attempting to import it using ES Modules syntax (e.g., `import`) will likely result in runtime errors in modern Node.js environments without proper transpilation or wrapper.
instrument
wrong
```
const { instrument } = require('menoetius'); // or instrument(app);
```
correct
```
menoetius.instrument(app);
```
The `instrument` function is exposed as a method on the default export object. It's not a named export and should be called directly on the imported `menoetius` object.

Quickstart

Demonstrates how to integrate Menoetius with an Express.js application to automatically expose request duration and system metrics on a custom `/metrics-data` endpoint.

const express = require('express');
const http = require('http');
const menoetius = require('menoetius');

const app = express();

// Instrument the Express application
menoetius.instrument(app, { url: '/metrics-data' });

app.get('/', (req, res) => {
  // Simulate some work
  const delay = Math.random() * 200; // 0-200ms
  setTimeout(() => {
    res.status(200).send('Hello from Menoetius-instrumented Express!');
  }, delay);
});

app.get('/slow', (req, res) => {
  // Simulate a slower response
  const delay = Math.random() * 1500 + 500; // 500-2000ms
  setTimeout(() => {
    res.status(200).send('This was a bit slower, check metrics!');
  }, delay);
});

app.get('/error', (req, res) => {
  // Simulate an error response
  res.status(500).send('An internal server error occurred!');
});

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Express server listening on port ${PORT}`);
  console.log(`Metrics available at http://localhost:${PORT}/metrics-data`);
  console.log('Try hitting /, /slow, and /error endpoints.');
});