@push.rocks/smartmetrics

A package for easy collection and reporting of system and process metrics.

readme.md for @push.rocks/smartmetrics

Powerful system metrics collection for Node.js applications with Prometheus integration 🚀

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What is SmartMetrics?

SmartMetrics is a comprehensive metrics collection library that monitors your Node.js application's resource usage in real-time. It tracks CPU usage, memory consumption, and system metrics across your main process and all child processes, providing insights through both JSON and Prometheus formats.

Key Features

Installation

pnpm install @push.rocks/smartmetrics
# or
npm install @push.rocks/smartmetrics

Quick Start

import { SmartMetrics } from '@push.rocks/smartmetrics';
import { Smartlog } from '@push.rocks/smartlog';

// Create a logger instance
const logger = new Smartlog({
  logContext: null,
  minimumLogLevel: 'info',
});
logger.enableConsole();

// Initialize SmartMetrics
const metrics = new SmartMetrics(logger, 'my-service');

// Get metrics on-demand
const currentMetrics = await metrics.getMetrics();
console.log(`CPU Usage: ${currentMetrics.cpuUsageText}`);
console.log(`Memory: ${currentMetrics.memoryUsageText}`);

// Enable automatic heartbeat logging (every 20 seconds)
metrics.start();

// Enable Prometheus endpoint
metrics.enablePrometheusEndpoint(9090);
// Metrics now available at http://localhost:9090/metrics

// Clean shutdown
metrics.stop();

Core Concepts

Process Aggregation

SmartMetrics doesn't just monitor your main process – it automatically discovers and aggregates metrics from all child processes spawned by your application using pidtree. This gives you a complete picture of your application's resource footprint, not just the parent process.

Memory Limit Detection

The library automatically detects available memory whether running on bare metal, in Docker containers, or with Node.js heap restrictions. It picks the most restrictive of:

  1. System total memory (os.totalmem())
  2. Docker cgroup limit – supports both cgroup v2 (/sys/fs/cgroup/memory.max) and cgroup v1 (/sys/fs/cgroup/memory/memory.limit_in_bytes)
  3. V8 heap size limit (v8.getHeapStatistics().heap_size_limit)

This ensures accurate percentage calculations regardless of environment.

Dual Output Formats

API Reference

new SmartMetrics(logger, sourceName)

Creates a new SmartMetrics instance.

Parameter Type Description
logger Smartlog A @push.rocks/smartlog logger instance
sourceName string Identifier for your service/application

async getMetrics(): Promise<IMetricsSnapshot>

Retrieves current system metrics as a structured object.

Returns IMetricsSnapshot:

{
  process_cpu_seconds_total: number;    // Total CPU time in seconds
  nodejs_active_handles_total: number;   // Always 0 (deprecated Node.js API; real values tracked by Prometheus default collectors)
  nodejs_active_requests_total: number;  // Always 0 (deprecated Node.js API; real values tracked by Prometheus default collectors)
  nodejs_heap_size_total_bytes: number;  // V8 heap size in bytes
  cpuPercentage: number;                 // Aggregated CPU usage across all child processes
  cpuUsageText: string;                  // Human-readable CPU usage (e.g. "12.5 %")
  memoryPercentage: number;              // Memory usage as percentage of detected limit
  memoryUsageBytes: number;              // Total memory in bytes across all child processes
  memoryUsageText: string;               // Human-readable (e.g. "45% | 920 MB / 2 GB")
}

Example:

const metrics = await smartMetrics.getMetrics();
if (metrics.cpuPercentage > 80) {
  console.warn('High CPU usage detected!');
}

start(): void

Starts automatic metrics collection and heartbeat logging every 20 seconds via the provided Smartlog instance.

smartMetrics.start();
// Logs: "sending heartbeat for my-service with metrics" every 20 seconds

stop(): void

Stops automatic metrics collection, closes heartbeat loop, and shuts down any open Prometheus endpoints.

async getPrometheusFormattedMetrics(): Promise<string>

Returns all metrics in Prometheus text exposition format, including default Node.js collectors and custom SmartMetrics gauges.

const promMetrics = await smartMetrics.getPrometheusFormattedMetrics();
// Returns:
// # HELP smartmetrics_cpu_percentage Current CPU usage percentage
// # TYPE smartmetrics_cpu_percentage gauge
// smartmetrics_cpu_percentage 15.2
// # HELP smartmetrics_memory_percentage Current memory usage percentage
// # TYPE smartmetrics_memory_percentage gauge
// smartmetrics_memory_percentage 45.3
// # HELP smartmetrics_memory_usage_bytes Current memory usage in bytes
// # TYPE smartmetrics_memory_usage_bytes gauge
// smartmetrics_memory_usage_bytes 965214208
// ... plus all default Node.js metrics from prom-client

enablePrometheusEndpoint(port?: number): void

Starts an HTTP server that exposes metrics at /metrics for Prometheus scraping.

Parameter Type Default Description
port number 9090 Port to listen on 
smartMetrics.enablePrometheusEndpoint(3000);
// GET http://localhost:3000/metrics → Prometheus text format
// GET http://localhost:3000/anything-else → 404

disablePrometheusEndpoint(): void

Gracefully shuts down the Prometheus HTTP server.

formatBytes(bytes, decimals?): string

Utility method to convert byte values to human-readable strings.

smartMetrics.formatBytes(1073741824); // "1 GB"
smartMetrics.formatBytes(1536, 1);    // "1.5 KB"

Use Cases

🔍 Application Performance Monitoring

const metricsBefore = await smartMetrics.getMetrics();
await performHeavyOperation();
const metricsAfter = await smartMetrics.getMetrics();

console.log(`Operation consumed ${
  metricsAfter.process_cpu_seconds_total - metricsBefore.process_cpu_seconds_total
} CPU seconds`);

🛡️ Resource Limit Enforcement

async function checkResources() {
  const metrics = await smartMetrics.getMetrics();

  if (metrics.memoryPercentage > 90) {
    throw new Error('Memory usage too high, refusing new operations');
  }

  if (metrics.cpuPercentage > 95) {
    await delay(1000); // Back off when CPU is stressed
  }
}

📈 Prometheus + Grafana Stack

smartMetrics.enablePrometheusEndpoint(9090);

// prometheus.yml:
// scrape_configs:
//   - job_name: 'my-app'
//     scrape_interval: 15s
//     static_configs:
//       - targets: ['localhost:9090']

🐳 Container Resource Monitoring

// Automatically detects Docker/cgroup memory limits
const metrics = await smartMetrics.getMetrics();
console.log(metrics.memoryUsageText);
// Output: "45% | 920 MB / 2 GB" (container limit detected)

🔄 Health Check Endpoint

import express from 'express';

const app = express();

app.get('/health', async (req, res) => {
  const metrics = await smartMetrics.getMetrics();

  res.json({
    status: metrics.memoryPercentage < 90 ? 'healthy' : 'degraded',
    cpu: metrics.cpuUsageText,
    memory: metrics.memoryUsageText,
  });
});

🔁 Graceful Restart on High Memory (PM2)

setInterval(async () => {
  const metrics = await smartMetrics.getMetrics();

  if (metrics.memoryPercentage > 95) {
    console.error('Memory limit reached, requesting restart');
    process.exit(0); // PM2 will restart the process
  }
}, 10000);

This repository contains open-source code licensed under the MIT License. A copy of the license can be found in the LICENSE file.

Please note: The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH or third parties, and are not included within the scope of the MIT license granted herein.

Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines or the guidelines of the respective third-party owners, and any usage must be approved in writing. Third-party trademarks used herein are the property of their respective owners and used only in a descriptive manner, e.g. for an implementation of an API or similar.

Company Information

Task Venture Capital GmbH Registered at District Court Bremen HRB 35230 HB, Germany

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.

changelog.md for @push.rocks/smartmetrics

2026-03-23 - 3.0.3 - fix(prometheus)

clean up default Prometheus metric collectors on stop

2026-03-02 - 3.0.2 - fix(pidusage)

prune history entries for PIDs not present in the requested set to avoid stale data and memory growth

2026-02-19 - 3.0.1 - fix(smartmetrics)

no code changes detected; no version bump or release required

2026-02-19 - 3.0.0 - BREAKING CHANGE(smartmetrics)

add system-wide metrics collection, Prometheus gauges, and normalized CPU reporting

2026-02-19 - 2.0.11 - fix(deps)

bump dependencies, update build script, expand README and npm metadata

2025-06-09 - 2.0.9 - fix(readme)

Update documentation with detailed usage instructions, API references and integration examples.

2025-06-09 - 2.0.8 - fix(smartmetrics)

Refactor metrics calculation and update Prometheus integration documentation

2025-06-09 - 2.0.7 - Prometheus Metrics Integration

feat: Implement Prometheus metrics exposure in SmartMetrics

2023-07-02 to 2023-08-08 - 2.0.0 to 2.0.6 - Maintenance Updates

Over this period several releases were published with iterative fixes and minor organizational changes.

2021-08-12 to 2022-07-27 - 1.0.1 to 1.0.17 - Maintenance and Breaking Changes

During this interval a series of minor fixes were combined with a significant breaking change.