Telegraf Custom Builder Guide

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What if you don’t like the default plugins or want to add some new ones? Well, bro, you’re in luck because I’m going to teach you how to build your own Telegraf plugins using nothing but a spoon and a can-opener (or maybe just a text editor).

First things first why you might want to customize Telegraf. Maybe you have some proprietary software that doesn’t come with any built-in metrics, or perhaps you need to monitor something specific that isn’t covered by the default plugins. Whatever your reason may be, building a custom plugin can save you time and money in the long run (not to mention it’s pretty cool).

So how do we get started? Well, first things first let’s create a new directory for our plugin. We’ll call this one “my_plugin” because that sounds like a good name. Inside of this directory, we’re going to add two files: `my_plugin.go` and `README.md`.

The `my_plugin.go` file is where the magic happens it’s where you write your custom plugin code. The `README.md` file is optional but highly recommended, as it can help other people understand what your plugin does and how to use it.

Now the structure of a Telegraf plugin. At its core, a plugin consists of two main parts: an input and an output. The input collects data from some source (e.g., a database or a sensor), while the output sends that data to another location for analysis (e.g., InfluxDB).

For our example, let’s say we want to monitor the temperature of a room using a custom plugin. We’ll collect this data from a simple thermometer and send it to Telegraf for processing. Here’s what our `my_plugin.go` file might look like:

// Package declaration
package my_plugin

// Import necessary packages
import (
    "encoding/json" // Package for encoding and decoding JSON data
    "fmt" // Package for formatting and printing
    "net/http" // Package for making HTTP requests
    "time" // Package for handling time-related operations
)

// Struct for representing a thermometer
type Thermometer struct {
    URL string // URL of the thermometer
}

// Initialization function for registering the plugin with Telegraf
func init() {
    // Register the plugin with Telegraf
    err := Agent.Service("my_plugin", func() error {
        return Plugins.Add("thermometer", &ThermometerPlugin{})
    })
    if err != nil {
        fmt.Println(err)
    }
}

// Struct for representing the thermometer plugin
type ThermometerPlugin struct{}

// Function for providing sample configuration for the plugin
func (p *ThermometerPlugin) SampleConfig() interface{} {
    return map[string]interface{}{
        "url": string("http://example.com/temperature"), // Replace this with your own URL
    }
}

// Struct for representing the temperature data
type Temperature struct {
    Value float64 `json:"value"` // Value of the temperature
}

// Function for gathering data from the thermometer
func (p *ThermometerPlugin) Gather(acc chan<- Accumulator) error {
    // Get the configuration for the plugin
    config := p.Config().(*map[string]interface{})
    // Get the URL from the configuration
    url, ok := config["url"].(string)
    if !ok {
        return fmt.Errorf("missing required configuration: %s", "url")
    }

    // Make a HTTP GET request to the thermometer URL
    response, err := http.Get(url)
    if err != nil {
        return fmt.Errorf("error fetching temperature data from URL: %w", err)
    }
    defer response.Body.Close()

    // Decode the response body into a Temperature struct
    var temp Temperature
    err = json.NewDecoder(response.Body).Decode(&temp)
    if err != nil {
        return fmt.Errorf("error decoding temperature data from JSON: %w", err)
    }

    // Send the temperature data to the accumulator channel
    acc <- Accumulator{
        Fields: map[string]interface{}{"temperature": temp.Value}, // Add temperature data to the fields
        Tags:   map[string]string{"host": "my_server"}, // Replace this with your own hostname or IP address
    }

    return nil
}

Let’s break down what’s happening here. First, we import the necessary packages (encoding/json, net/http, and time). Then, we define a `Thermometer` struct that contains our URL for fetching temperature data. Next, we register our plugin with Telegraf using the `init()` function.

Inside of this function, we call the `Agent.Service(“my_plugin”, func() error { … })` method to add a new service called “my_plugin” that uses our custom plugin (which is defined in the `ThermometerPlugin` struct). We also pass an anonymous function as an argument to this method this function returns an error if there’s any problem with adding the service.

The `SampleConfig()` and `Gather()` methods are where we define our input (i.e., how we collect data) and output (i.e., what we do with that data). In this case, we fetch temperature data from a URL using HTTP GET, decode it into a struct called `Temperature`, and then send the resulting Accumulator to Telegraf for processing.

And there you have it your very own custom plugin! Of course, this is just one example of what’s possible with Telegraf plugins. You can get creative and add all sorts of functionality using Go (or any other language that supports the Telegraf plugin API). So give it a try who knows, you might end up creating something truly amazing!

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