Creating a Prometheus Exporter in Go

Introduction
Prerequisites
Setting up the Project
Creating a Prometheus Exporter
Running and Testing the Exporter
Conclusion

Introduction

In this tutorial, we will learn how to create a Prometheus exporter in Go. Prometheus is a popular open-source monitoring and alerting toolkit, and exporters are components that expose metrics in a format that Prometheus can understand. By the end of this tutorial, you will be able to create your own exporter to monitor your Go applications and systems.

Prerequisites

Before starting the tutorial, you should have the following:

Basic understanding of the Go programming language
Go installed on your machine (version 1.11 or later)
Basic knowledge of metrics and monitoring concepts

Setting up the Project

To begin, let’s set up a new Go project for our Prometheus exporter.

Create a new directory for your project:

```shell
mkdir prometheus-exporter
cd prometheus-exporter
```

Initialize a new Go module:

```shell
go mod init github.com/your-username/prometheus-exporter
```

Create a new Go file called main.go:
```
```shell
touch main.go
```
```

Creating a Prometheus Exporter

In this section, we will create a simple Prometheus exporter that exposes a custom metric.

Open the main.go file in your preferred editor.

Import the necessary packages:

```go
package main

import (
	"fmt"
	"net/http"

	"github.com/prometheus/client_golang/prometheus"
)
```

Define a custom metric. Let’s say we want to track the number of HTTP requests made to our application:

```go
var (
	totalRequests = prometheus.NewCounter(prometheus.CounterOpts{
		Name: "http_requests_total",
		Help: "Total number of HTTP requests",
	})
)
```

Initialize the Prometheus exporter:

```go
func init() {
	prometheus.MustRegister(totalRequests)
}
```

Implement a simple HTTP handler to handle incoming requests:

```go
func handler(w http.ResponseWriter, r *http.Request) {
	totalRequests.Inc()
	fmt.Fprint(w, "Hello, World!")
}
```

```go
func main() {
	http.HandleFunc("/", handler)
	http.Handle("/metrics", prometheus.Handler())

	fmt.Println("Server started on http://localhost:8080")
	http.ListenAndServe(":8080", nil)
}
```

Here, we register our custom handler to handle requests and the `/metrics` endpoint to expose metrics.

Finally, run the program:

```shell
go run main.go
```

Your Prometheus exporter is now running!

Running and Testing the Exporter

Now that our Prometheus exporter is up and running, let’s test it and see how we can scrape the metrics.

Open your web browser and navigate to http://localhost:8080/. You should see the message “Hello, World!”.

Open another tab and visit http://localhost:8080/metrics. You should see the Prometheus metrics output, including our custom metric http_requests_total.

```
# HELP http_requests_total Total number of HTTP requests
# TYPE http_requests_total counter
http_requests_total 4
```

Here, the `http_requests_total` metric has a value of 4 since we visited the `/` endpoint four times.

To scrape these metrics using Prometheus, add the following configuration to your prometheus.yml file:

```yaml
scrape_configs:
  - job_name: 'my_exporter'
    static_configs:
      - targets: ['localhost:8080']
```

Prometheus will now scrape the metrics from our exporter.

Restart Prometheus and navigate to the Prometheus web interface. You should see the http_requests_total metric in the list of available metrics.
Create a graph or dashboard to visualize the http_requests_total metric over time.

Congratulations! You have successfully created a Prometheus exporter in Go and exposed a custom metric for monitoring.

Conclusion

In this tutorial, we learned how to create a Prometheus exporter in Go. We covered the basics of setting up a Go project, creating a custom metric, and exposing it for monitoring using Prometheus. By following the steps in this tutorial, you can now create your own exporters to monitor various aspects of your applications and systems using Prometheus.

Remember to explore the Prometheus documentation and other available client libraries to further enhance your understanding and capabilities with Prometheus monitoring. Happy monitoring!

Published: 22 January 2023