M2-E-03.md

Module 2 Extra 3: Inventory Management in Go for Containerlab*

Concept:

Programmatically obtaining information about deployed Containerlab nodes (IPs, names) to build an inventory in Go, which is essential for scaling automation.

Challenge:

Write a Go program that parses the srl_2_nodes.clab.yaml file (or directly queries Containerlab if possible, but parsing YAML is more direct for this exercise) to extract the hostnames and expected management IPs of the SR Linux nodes.

Code Example:

// main.go
package main

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

type Topology struct {
	Name     string   `yaml:"name"`
	Topology TopoBody `yaml:"topology"`
}

type TopoBody struct {
	Nodes map[string]Node `yaml:"nodes"`
	Links []Link          `yaml:"links"`
}

type Node struct {
	Kind          string `yaml:"kind"`
	Image         string `yaml:"image"`
	StartupConfig string `yaml:"startup-config"`
}

type Link struct {
	Endpoints []string `yaml:"endpoints"`
}

func main() {
	data, err := os.ReadFile("srl_2_nodes.clab.yaml")
	if err != nil {
		panic(err)
	}

	var topo Topology
	if err := yaml.Unmarshal(data, &topo); err != nil {
		panic(err)
	}
	fmt.Printf("Containerlab Lab Name: %s\n", topo.Name)
	fmt.Println("Discovered SR Linux Nodes:")
	for nodeName, nodeDetails := range topo.Topology.Nodes {
		fmt.Printf("Node Name: %s, Kind: %s, Image: %s\n", nodeName, nodeDetails.Kind, nodeDetails.Image)
	}
}

Instructions:

1. Ensure srl_2_nodes.clab.yaml is present from Day 9.
2. Run go mod init day10.
3. Run go get gopkg.in/yaml.v2.
4. Save the code as main.go.
5. Run go run main.go.