How to create custom json structure (ansible inventory) - json

Question

I am obtaining data from the cloudstack API listVirtualMachines, and trying to create a web service that will provide a dynamic ansible inventory for certain hosts.
In my first tries, currently I am fetching all the data by doing a connection request and then within a loop parse all the output:
vms, _ := cs.Request(&cs.ListVirtualMachines{})
// use for the metadata _meta['hostvars']['IP']['key'] = val
hostvars := make(map[string]map[string]string)
// used per each host ['name']['hosts'] = [list]
hosts := make(map[string]map[string][]string)
for _, vm := range vms(*cs.ListVirtualMachinesResponse).VirtualMachine {
ip := vm.Nic[0].IPAddress.String()
if ip == "" {
continue
}
hostvars[ip] = map[string]string{
vm.DisplayName: vm.DisplayName,
"ansible_ssh_common_args": "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null",
}
if hosts[vm.DisplayName] == nil {
hosts[vm.DisplayName] = map[string][]string{}
}
hosts[vm.DisplayName]["hosts"] = append(hosts[vm.DisplayName]["hosts"], ip)
}
My desired output needs this JSON format:
{
"_meta": {
"hostvars": {
"172.16.0.3": {
"ansible_ssh_common_args": "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null",
"displayname": "server 1"
},
"172.16.0.4": {
"ansible_ssh_common_args": "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null",
"displayname": "server 2"
},
"172.16.0.5": {
"ansible_ssh_common_args": "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null",
"displayname": "server 3"
}
}
},
"group1": {
"hosts": [
"172.16.0.3",
"172.16.0.4",
"172.16.0.5"
]
},
"sandbox": {
"children": [
"server1",
"server2",
"server3"
]
},
"server1": {
"hosts": [
"172.16.0.3"
]
},
"server2": {
"hosts": [
"172.16.0.4"
]
},
"server3": {
"hosts": [
"172.16.0.5"
]
}
}
My first try was to create a huge map:
inventory := map[string]map[string]map[string]string{}
But that was covering only the structure of the _meta key :
{
"_meta": {
"hostvars": {
"x.x.x.x": {
"key": "value"
},
"x.x.x.y": {
"key": "value"
}
}
}
}
Later I came with a struct:
type Ansible struct {
Metadata Hostvars `json:"_meta"`
Hosts map[string]map[string][]string `json:",inline"` // want to remove the Hosts key
}
type Hostvars struct {
Hosts map[string]map[string]string `json:"hostvars"`
}
inventory := &Ansible{
Hostvars{hostvars},
hosts,
}
if err := json.NewEncoder(os.Stdout).Encode(inventory); err != nil {
log.Println(err)
}
The problem with this approach is that the returned JSON is adding both keys _meta and hosts:
{
"_meta": {
"hostvars": {
"x.x.x.x": {
"key": "value"
},
"x.x.x.y": {
"key": "value"
}
}
},
"hosts": { <--- want to remove this
"server1": {
"hosts": [
"172.16.0.3"
]
}
...
}
}
I would like to just have the key _meta and at the same level (inline) have each key for every hostname, something like:
{
"_meta": {...},
"server1": {
"hosts": []
},
"group1": {
"hosts": []
},
"sandbox": {
"children": []
}
}
I have a guess this probably could be solved with a map[string]interface{} maybe that could allow a dynamic JSON object with dynamic key names/structure, don't know exactly, therefore, any help would be appreciated.

Answer 1

You best bet is probably to let Ansible implement json.Marshaler to "flatten" the JSON document on-the-fly.
package main
import (
"encoding/json"
"fmt"
)
func main() {
a := &Ansible{
Metadata: Hostvars{
Hosts: map[string]map[string]string{
"172.16.0.3": map[string]string{
"displayname": "server 1",
},
},
},
Hosts: map[string]Group{
"group1": Group{Hosts: []string{"172.16.0.3", "172.16.0.4", "172.16.0.5"}},
"sandbox": Group{Children: []string{"server1", "server2", "server3"}},
"server1": Group{Hosts: []string{"172.16.0.3"}},
},
}
b, err := json.MarshalIndent(a, "", " ")
fmt.Println(string(b), err)
}
type Ansible struct {
Metadata Hostvars
Hosts map[string]Group
}
type Hostvars struct {
Hosts map[string]map[string]string `json:"hostvars"`
}
// I don't *think* Ansible supports anything else in host groups, so it makes
// sense to define it as a struct.
type Group struct {
Hosts []string `json:"hosts,omitempty"`
Children []string `json:"children,omitempty"`
}
// MarshalJSON implements json.Marshaler
func (a *Ansible) MarshalJSON() ([]byte, error) {
// Define a map that we will encode at the end of the function.
doc := make(map[string]interface{})
// Add all the groups.
for k, v := range a.Hosts {
doc[k] = v
}
// Add the _meta key.
doc["_meta"] = a.Metadata
return json.Marshal(doc)
}
Try it on the playground: https://play.golang.org/p/OKQHAG3vqIG