Introduction

Prometheus is a powerful monitoring system designed to collect metrics from various sources. However, not all applications and systems natively expose their metrics in a Prometheus-compatible format. This is where exporters come into play. Exporters act as bridges between Prometheus and external systems, exposing metrics in a format that Prometheus can scrape and store.

In this article, we will explore:

• The available Prometheus exporters for different use cases.

• How exporters work in the backend to collect and expose metrics.

1. What Are Exporters in Prometheus?

Exporters are services that collect metrics from applications, operating systems, databases, or hardware and expose them in Prometheus' exposition format.

Prometheus then scrapes these metrics from the exporters at predefined intervals and stores them in its Time Series Database (TSDB).

How Exporters Work in Prometheus?

1. Collect Raw Data – The exporter gathers raw metrics from an application, system, or service.

2. Format Data for Prometheus – Converts the collected data into Prometheus' exposition format.

3. Expose an HTTP Endpoint – Makes metrics available over an HTTP endpoint (/metrics).

4. Prometheus Scrapes Data – Prometheus periodically queries the endpoint, processes the data, and stores it in TSDB.

Example Workflow

• Exporter: node_exporter collects system-level metrics.

• Exposes metrics at: http://localhost:9100/metrics

• Prometheus scrapes it using the configuration:

    scrape_configs:
      - job_name: "node"
        static_configs:
          - targets: ["localhost:9100"]
  

• Metrics stored in TSDB and queried using PromQL

2. Commonly Used Prometheus Exporters

Prometheus supports a wide range of exporters, categorized based on the systems they monitor.

A. Node and System Exporters

B. Database Exporters

C. Cloud and Kubernetes Exporters

D. Application-Specific Exporters

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3. How Prometheus Exporters Work in the Backend

Exporters interact with Prometheus by collecting, processing, and exposing metrics. Here’s a step-by-step look at how they operate in the backend:

Step 1: Data Collection

• The exporter queries the system, application, or database for real-time metrics.

• It may use API calls, logs, command outputs, or direct system queries.

• Example: Node Exporter reads from /proc and /sys directories in Linux.

Step 2: Metric Formatting

• Exporters structure the collected data in Prometheus' exposition format.

• Example:

    # HELP node_cpu_seconds_total Seconds the CPU spent in each mode.
    # TYPE node_cpu_seconds_total counter
    node_cpu_seconds_total{cpu="0", mode="user"} 1234.56
  

• This format includes:

  • Metric name (node_cpu_seconds_total)

  • Labels (metadata) (cpu="0", mode="user")

  • Metric type (counter)

  • Value (1234.56)

Step 3: Exposing an HTTP Endpoint

• Exporters expose an HTTP endpoint (/metrics) where Prometheus scrapes data.

• Example:

  • http://localhost:9100/metrics (Node Exporter)

  • http://localhost:9187/metrics (PostgreSQL Exporter)

Step 4: Prometheus Scrapes the Data

• Prometheus regularly fetches metrics by making HTTP GET requests.

• Example:

    curl http://localhost:9100/metrics
  

• Scraped metrics are stored in Prometheus TSDB.

Step 5: Querying & Visualization

• Metrics can be queried using PromQL.

• Example:

    rate(http_requests_total[5m])
  

• Data is visualized using Grafana dashboards.

4. Configuring Prometheus to Scrape Exporters

To integrate an exporter with Prometheus, add a scrape job in prometheus.yml.

Example: Configuring Node Exporter

scrape_configs:
  - job_name: "node"
    static_configs:
      - targets: ["localhost:9100"]

Example: Configuring PostgreSQL Exporter

scrape_configs:
  - job_name: "postgres"
    static_configs:
      - targets: ["localhost:9187"]

Restart Prometheus to apply changes:

systemctl restart prometheus

Conclusion

Prometheus exporters are essential for collecting metrics from various sources. Understanding how they work in the backend helps in: Configuring monitoring for different systems. Optimizing metric collection and storage Troubleshooting exporter-related issues

Exporters are the backbone of Prometheus-based monitoring, providing seamless integration with diverse platforms like operating systems, databases, cloud services, and applications.