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https://github.com/neonsludge/ansible-dns-inventory
A tool that processes sets of host attributes stored as DNS TXT records or key/value pairs in etcd to create a tree-like inventory of your infrastructure that can be immediately consumed by Ansible or exported in several helpful formats.
https://github.com/neonsludge/ansible-dns-inventory
ansible ansible-dynamic-inventory ansible-inventories ansible-inventory automation configuration-management dns-inventory dynamic-inventories dynamic-inventory inventory
Last synced: about 1 month ago
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A tool that processes sets of host attributes stored as DNS TXT records or key/value pairs in etcd to create a tree-like inventory of your infrastructure that can be immediately consumed by Ansible or exported in several helpful formats.
- Host: GitHub
- URL: https://github.com/neonsludge/ansible-dns-inventory
- Owner: NeonSludge
- License: mit
- Created: 2019-11-06T14:48:40.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2024-08-05T08:30:47.000Z (3 months ago)
- Last Synced: 2024-09-30T01:42:40.340Z (about 1 month ago)
- Topics: ansible, ansible-dynamic-inventory, ansible-inventories, ansible-inventory, automation, configuration-management, dns-inventory, dynamic-inventories, dynamic-inventory, inventory
- Language: Go
- Homepage:
- Size: 209 KB
- Stars: 15
- Watchers: 5
- Forks: 2
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# ansible-dns-inventory
[](https://goreportcard.com/report/github.com/NeonSludge/ansible-dns-inventory)
[](https://pkg.go.dev/github.com/NeonSludge/ansible-dns-inventory)
A CLI tool (and a library) that processes sets of host attributes stored as DNS TXT records or key/value pairs in etcd to create a tree-like inventory of your infrastructure. It can be used directly as an Ansible [dynamic inventory script](https://docs.ansible.com/ansible/latest/user_guide/intro_dynamic_inventory.html) or export the inventory in several helpful formats.
## Features
- Files and environment variables are supported as configuration sources.
- DNS and etcd are available as data sources.
- **(DNS data source)** two modes of operation: zone transfers and regular DNS queries.
- **(DNS data source)** TSIG support for zone transfers.
- **(Etcd data source)** authentication and mTLS support.
- **(Etcd data source)** importing host records from a YAML file.
- Unlimited number and length of inventory tree branches.
- Predictable and stable inventory structure.
- Multiple records per host supported.
- Optional custom Ansible variables in host records (see caveats in the 'Host variables' section).
- Can be used as a library.
## Usage
```txt
Usage of dns-inventory:
-attrs
export host attributes
-format string
select export format, if available (default "yaml")
-groups
export groups
-host string
produce a JSON dictionary of host variables for Ansible
-hosts
export hosts
-import string
import host records from file
-list
produce a JSON inventory for Ansible
-tree
export raw inventory tree
-version
display ansible-dns-inventory version and build info
```
## Prerequisites
### DNS data source
1. Allow zone transfers (AXFR) from your DNS server to the host that is going to be running the `dns-inventory` utility and setup TSIG parameters in the configuration file (if needed) or use the no-transfer mode (the `dns.notransfer.enabled` parameter).
2. Add one or more properly formatted DNS TXT records either for the managed hosts themselves or for a special host (the `dns.notransfer.host` parameter) if you're using the no-transfer mode.
3. Set other relevant parameters in the configuration file or via environment variables.
### Etcd data source
1. Add one or more properly formatted key/value pairs for all managed hosts.
2. Set other relevant parameters in the configuration file or via environment variables.
## Configuration file
`ansible-dns-inventory` can use a YAML configuration file, a set of environment variables or both as its configuration source.
It will try to load the file specified in the `ADI_CONFIG_FILE` environment variable if it is defined.
If this variable is not defined or has an empty value, it looks for an `ansible-dns-inventory.yaml` file inside these directories (in this specific order):
1. current working directory
2. `/.ansible/`
3. `/etc/ansible/`
`ansible-dns-inventory` will panic if a configuration file was found but there was a problem reading it.
If no configuration file was found, it will fall back to using default values and environment variables.
Every parameter can also be overriden by a corresponding environment variable.
There is a [template](config/ansible-dns-inventory.yaml) in this repository that lists descriptions, environment variable names and default values for all available parameters.
### Example of a config file
```yaml
datasource: dns
dns:
server: "10.100.100.1:53"
timeout: "120s"
zones:
- server.local.
- infra.local.
etcd:
endpoints:
- 10.100.100.1:2379
- 10.100.100.2:2379
- 10.100.100.3:2379
tls:
insecure: true
txt:
kv:
separator: "|"
keys:
env: "PRJ"
```
## Host records
### DNS data source
There are two ways to add a host to the inventory:
1. Create a DNS TXT record for this host and format it properly, specifying host attributes as a set of key/value pairs. One host can have an unlimited number of TXT records: all of them will be parsed by `ansible-dns-inventory`.
2. Enable the no-transfer mode, add a TXT record for the special host (`ansible-dns-inventory.your.domain` by default) and format it properly, referencing the host you want to add to your inventory and specifying its attributes as a set of key/value pairs. Again, one host can have any number of records here.
Here is an example of using both of these ways:
#### Example of a DNS TXT record (regular mode)
| Host | TXT record |
| --------------------- | -------------------------------------------------------------------------------- |
| `app01.infra.local` | `OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_auth;VARS=key1=value1,key2=value2` |
#### Example of a DNS TXT record (no-transfer mode)
| Host | TXT record |
| ----------------------------------- | -------------------------------------------------------------------------------------------------- |
| `ansible-dns-inventory.infra.local` | `app01.infra.local:OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_auth;VARS=key1=value1,key2=value2` |
The separator between the hostname and the attribute string in the no-transfer mode is customizable (the `dns.notransfer.separator` parameter).
### Etcd data source
There is only one way of adding host records to an etcd data source.
You create a key/value pair where the value is formatted the same way as with the DNS data source and the key name must be constructed by strictly following this scheme:
`///`
...where:
- `` is the same as the `etcd.prefix` configuration parameter value
- `` is one of the zones listed in the `etcd.zones` parameter
- `` is the FQDN of a host
- `` starts at 0 and is incremented for each additional record belonging to the same host.
#### Example of a key/value pair
| Key | Value |
| ---------------------------------------------------- | -------------------------------------------------------------------------------- |
| `ANSIBLE_INVENTORY/infra.local./app01.infra.local/0` | `OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_auth;VARS=key1=value1,key2=value2` |
### Host attributes (default keys)
| Key | Description |
| ---- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| OS | Operating system identifier. Required. |
| ENV | Environment identifier. Required. |
| ROLE | Host role identifier(s). Required. Can be a comma-delimited list. |
| SRV | Host service identifier(s). This will be split further using the `txt.keys.separator` to produce a hierarchy of groups. Required. Can also be a comma-delimited list. |
| VARS | Optional host variables. |
All keys and separators are customizable via `ansible-dns-inventory`'s config file.
Values are validated and can only contain numbers and letters of the Latin alphabet, except for the service identifier(s) which can also contain the `txt.keys.separator` symbol.
All host attributes (except for `VARS`) can be referenced by their keys in Ansible code via the `inventory_attributes` group variable. Its availability doesn't depend on the host variables feature (see below).
### Host variables
`ansible-dns-inventory` supports passing additional host variables to Ansible via the `VARS` attribute. This feature is disabled by default, you can enable it by setting the `txt.vars.enabled` parameter to `true`.
This is meant to be used in cases where storing some Ansible host variables directly in TXT records could be a good idea. For example, you might want to put variables like `ansible_user` there.
WARNING: This feature adds an additional DNS request for every host in your inventory so be careful when using it with large inventories.
The no-transfer mode may particularly suffer a perfomance hit if host variables are used.
## Inventory structure
In general, if you have a single TXT record for a `HOST` and this record has all 4 required attributes set then this `HOST` will end up in this hierarchy of groups:
```txt
@all:
|--@all_:
| |--@all__:
| | |--@all___:
| | | |--@all____..._:
| | | | |--
|--@all_host:
| |--@all_host_:
| | |--
|--@:
| |--@_:
| | |--@__:
| | | |--@___:
| | | | |--@____..._:
| | | | | |--
| |--@_host:
| | |--@_host_:
| | | |--
```
Let's say you have these records in your DNS server:
| Host | TXT record |
| ------------------- | ----------------------------------------------------- |
| `app01.infra.local` | `OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_auth` |
| `app02.infra.local` | `OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_auth` |
| `app03.infra.local` | `OS=linux;ENV=dev;ROLE=app;SRV=tomcat_backend_media` |
These will produce the following Ansible inventory tree:
```txt
@all:
|--@all_app:
| |--@all_app_tomcat:
| | |--@all_app_tomcat_backend:
| | | |--@all_app_tomcat_backend_auth:
| | | | |--app01.infra.local
| | | | |--app02.infra.local
| | | |--@all_app_tomcat_backend_media:
| | | | |--app03.infra.local
|--@all_host:
| |--@all_host_linux:
| | |--app01.infra.local
| | |--app02.infra.local
| | |--app03.infra.local
|--@dev:
| |--@dev_app:
| | |--@dev_app_tomcat:
| | | |--@dev_app_tomcat_backend:
| | | | |--@dev_app_tomcat_backend_auth:
| | | | | |--app01.infra.local
| | | | | |--app02.infra.local
| | | | |--@dev_app_tomcat_backend_media:
| | | | | |--app03.infra.local
| |--@dev_host:
| | |--@dev_host_linux:
| | | |--app01.infra.local
| | | |--app02.infra.local
| | | |--app03.infra.local
|--@ungrouped:
```
## Export mode
`ansible-dns-inventory` can also export the inventory in several formats. This makes it possible to use your inventory in some third-party software.
An example of this use case would be using this output as a dictionary in a [Logstash translate filter](https://www.elastic.co/guide/en/logstash/current/plugins-filters-translate.html#plugins-filters-translate-dictionary_path) to populate a `groups` field during log processing to be able to filter events coming from a specific group of hosts.
There are several export modes, which support different export formats.
| Flag | Description | Formats |
| --------- | ----------------------------------------------------------------------- | --------------------------------------- |
| `-hosts` | Export hosts, mapping each one to a list of groups. | `json`, `yaml`, `yaml-list`, `yaml-csv` |
| `-groups` | Export groups, mapping each one to a list of hosts. | `json`, `yaml`, `yaml-list`, `yaml-csv` |
| `-attrs` | Export hosts, mapping each one to a list of dictionaries of attributes. | `json`, `yaml`, `yaml-flow` |
| `-tree` | Export the raw inventory tree. | `json`, `yaml` |
The default format is always `yaml`.
The `-attrs` mode exports a list of dictionaries of attributes for each host. If a host has multiple TXT records or multiple elements in a comma-separated list in the `ROLE` or `SRV` attribute, the attribute list for this host in the `-attrs` output will contain multiple dictionaries: one for each detected attribute "set".
### Examples
```txt
$ dns-inventory -hosts -format yaml-list
...
"app01.infra.local": ["all", "all_app", "all_app_tomcat", "all_host", ...]
...
$ dns-inventory -hosts -format yaml-csv
...
"app01.infra.local": "all,all_app,all_app_tomcat,all_host,..."
...
$ dns-inventory -attrs -format yaml-flow
...
"app01.infra.local": [{"OS": "linux", "ENV": "dev", "ROLE": "app", "SRV": "tomcat_backend_auth", "VARS": "key1=value1,key2=value2"}]
...
```
## Import mode
Some `ansible-dns-inventory` datasources support importing host records from a YAML file. These currently include:
- etcd datasource
To populate one of these datasources with host records, first create a YAML file with the same structure as the `-attrs` export mode output:
```
# cat import.yaml
app01.infra.local:
- ENV: dev
OS: linux
ROLE: app
SRV: tomcat_backend_auth
VARS: ansible_host=10.0.0.1
app02.infra.local:
- ENV: dev
OS: linux
ROLE: app
SRV: tomcat_backend_auth
VARS: ansible_host=10.0.0.2
```
Custom host attribute keys will be expected here if set in the configuration (`txt.keys`).
Then run `ansible-dns-inventory` in the import mode:
```
dns-inventory -import ./import.yaml
```
## Roadmap
- [x] Implement key-value stores support (etcd, Consul, etc.).
- [x] Support using `ansible-dns-inventory` as a library.
- [x] Implement import mode for some of the datasources. (implemented for the etcd datasource)
- [ ] Support more datasource types.