Custom Exporters in Monitoring with Prometheus

Introduction

Prometheus is a powerful tool for monitoring and alerting. One of its strengths lies in its ability to collect metrics from various applications through custom exporters. This lesson will guide you through the creation and usage of custom exporters in Prometheus.

Key Concepts

• **Exporter**: A piece of code or service that collects metrics and exposes them in a format that Prometheus can scrape.
• **Metrics**: Quantifiable data points collected from applications or systems.
• **Scraping**: The process by which Prometheus collects metrics from configured endpoints.

Step-by-Step Process

1. Define the Metrics

Determine the metrics you want to expose. For example, application performance metrics such as request counts, error rates, and latency.

2. Create the Exporter

Use a programming language of your choice (e.g., Python, Go) to create the exporter. Below is an example in Python using the prometheus_client library.

from prometheus_client import start_http_server, Summary, Counter
import random
import time

# Create a metric to track request latency
REQUEST_LATENCY = Summary('request_latency_seconds', 'Time spent processing request')

# Create a counter for the number of requests
REQUEST_COUNT = Counter('request_count', 'Total number of requests')

@REQUEST_LATENCY.time()
def process_request():
    """A dummy function that takes some time to execute."""
    time.sleep(random.random())

if __name__ == '__main__':
    # Start up the server to expose the metrics.
    start_http_server(8000)
    while True:
        process_request()
        REQUEST_COUNT.inc()
    

3. Configure Prometheus to Scrape the Exporter

Add the following configuration to your Prometheus configuration file prometheus.yml:

scrape_configs:
  - job_name: 'custom_exporter'
    static_configs:
      - targets: ['localhost:8000']
    

4. Start the Exporter and Prometheus

Run your custom exporter script and ensure Prometheus is running. You can access the metrics at http://localhost:8000.

Best Practices

• Use consistent naming conventions for your metrics.
• Document your metrics and their meanings for future reference.
• Optimize your exporter to minimize performance impact on the application.
• Test your exporter thoroughly to ensure it exposes the correct metrics.

FAQ