How-to: Add a Transformer

This guide explains how to extend DNS-collector by creating a custom DNS transformer.

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1. Add Configuration

Define your transformer configuration struct in pkgconfig/transformers.go (or dnsutils/config.go):

type ConfigTransformers struct {
    MyTransform struct {
        Enable bool `yaml:"enable"`
    } `yaml:"mytransform"`
}

Set its default values:

func (c *ConfigTransformers) SetDefault() {
    c.MyTransform.Enable = false
}

---

2. Implement the Transformer

Create the transformer implementation in transformers/mytransform.go and unit tests in transformers/mytransform_test.go:

package transformers

import (
    "github.com/dmachard/go-dnscollector/v3/dnsutils"
    "github.com/dmachard/go-dnscollector/v3/pkgconfig"
    "github.com/dmachard/go-logger"
)

type MyTransform struct {
    *GenericTransformer
}

func NewMyTransform(config *pkgconfig.ConfigTransformers, logger *logger.Logger, name string, instance int, nextWorkers []chan dnsutils.DNSMessage) *MyTransform {
    t := &MyTransform{GenericTransformer: NewTransformer(config, logger, "mytransform", name, instance, nextWorkers)}
    return t
}

func (t *MyTransform) ProcessMessage(dm *dnsutils.DNSMessage) (int, error) {
    // Your custom DNS manipulation or enrichment logic here
    return ReturnSuccess, nil
}

---

3. Register the Transformer

Declare and initialize the transformer in transformers/transformers.go:

if config.MyTransform.Enable {
    // initialize transformer instance
}

---

4. Documentation & Tests

1. Add unit tests in transformers/mytransform_test.go.
2. Document the new transformer options in docs/transformers/ and update README.md.