prometheus_custom_exporter_node

A Node.js-based Prometheus exporter that dynamically loads and serves custom metrics from JavaScript files in a designated directory. The exporter uses the prom-client library to collect and serve metrics that can be scraped by Prometheus.

This exporter allows you to add new custom metrics simply by adding or modifying JavaScript files in the metrics directory. Each JavaScript file must export a function that registers custom metrics with the Prometheus Registry.

Features

• Dynamic Metric Loading: Automatically loads custom metric modules from a specified directory.
• Custom Metrics Support: Allows you to define custom metrics using the prom-client library.
• Hot Reloading: Detects changes in the metrics directory and reloads modified/added files automatically.
• Built-in Metrics: Optionally exposes default system and Node.js metrics through Prometheus.
• Lightweight: Uses Node.js’s built-in HTTP server without additional frameworks like Express.

Installation

1. Clone the repository:

   git clone https://github.com/liudonghua123/prometheus_custom_exporter_node.git
   cd prometheus_custom_exporter_node

2. Install dependencies:

   npm install

3. Create a metrics directory and add custom metric files (e.g., custom_metrics_1.js).

4. Run the exporter:

   node .

   The exporter will start an HTTP server on port 3000 (default) that exposes the /metrics endpoint. You can change the port by setting the PORT environment variable.

Metrics Directory Structure

• Create a metrics directory at the root of the project.
• Each file inside the metrics directory should export a function that registers custom metrics to the Prometheus Registry. The function will be executed every time the /metrics endpoint is accessed.

Example metric module: metrics/custom_metrics_1.js

import { Gauge } from 'prom-client';

console.info('Loaded metrics module: custom_metrics_1.js');

// Create a custom Gauge metric
const gauge = new Gauge({
  name: 'metric_name_1',
  help: 'Description of your metric'
});

// Export the function that will be called to register the metric
export default function process(registry) {
  // Set the value of the gauge
  gauge.set(10); // Set to 10, or set dynamic values based on your logic
  registry.registerMetric(gauge); // Register the metric with the Prometheus registry
}

How It Works

• The exporter loads all .js files from the metrics directory at startup.
• Each metric file should export a function that registers custom metrics using the prom-client library.
• When the /metrics endpoint is accessed, the exporter will call each of these functions and update the custom metrics.
• The /metrics endpoint is exposed on the default port 3000 (or the port defined by the PORT environment variable).

Hot Reloading

The exporter watches the metrics directory for changes and will automatically reload any new or modified metric files. This allows you to add or modify metrics without restarting the exporter.

Endpoints

• /metrics: Exposes the collected metrics in Prometheus text format.
• /default-metrics (optional): Exposes the built-in system and Node.js metrics collected by the prom-client library.

Configuration

• PORT: The port on which the exporter will run. Default is 3000. You can set it using the environment variable:

  PORT=8080 node .

• metrics directory: You can change the default ./metrics directory by modifying the metricsDir constant in the code.

Example Usage

Once the exporter is running, Prometheus can scrape the metrics by adding the following job to your Prometheus configuration (prometheus.yml):

scrape_configs:
  - job_name: 'custom_exporter'
    static_configs:
      - targets: ['localhost:3000']

Then you can access the metrics at http://localhost:3000/metrics.

Contributing

1. Fork the repository.
2. Clone your fork.
3. Create a new branch for your changes.
4. Submit a pull request with a description of your changes.

License

This project is licensed under the MIT License - see the LICENSE file for details.