Dynamic inventory script plugin configuration with custom binary

[pizzapill]

Hi guys,

I have trouble configuring a custom binary dynamic inventory plugin. I have the following configuration in inventory/serf.yml:

---
plugin: ansible.builtin.script
path: ../../serf_inv/target/debug/serf_inv

When I try to run it with ansible-inventory -i inventory/ --list -v I get a bunch of errors.

The documentation ansible-doc -t inventory script has no example and names only a single parameter: always_show_stderr. Therefore I’m pretty sure I’m doing something fundamentally wrong.

The binary works when I pass it directly: ansible-inventory -i ../../serf_inv/target/debug/serf_inv --list.

I tried to find examples etc. on Google but I couldn’t get any good results, partly because there is alot of documentation for the builtin script task. Thanks a lot for your help!

[bcoca (Brian Coca)]

use -i ../serf_inv/target/debug/serf_inv … the script inventory plugin does not use configuration, it expects any executable file that returns JSON.

[pizzapill]

Thanks a lot. Not the answer I was hoping for but it is what is is!

[bcoca (Brian Coca)]

not sure what you are trying/hoping to do, if you explain it, maybe i can help

[pizzapill]

Sure maybe there is another way.

Basically I have a binary that communicates with Serf to collect hosts, does some customization and spits out inventory JSON. This is written in Rust and I don’t want to touch Ansible plugin integration code and/or Python.

I would like to use this as a dynamic inventory source. This works when passing the binary directly as argument to the CLI programs (e.g. ansible-playbook -i path/binary playbook.yml). Basically what you suggested.

I rather have this configured as just another dynamic inventory source via yaml in my inventory directory. So I would have a inventory/serf.yml which calls the binary and i can just call ansible-playbook -i inventory/ playbook.yml.

As far as I understand currently I can provide either dynamic inventories via the available plugins (e.g. AWS) and/or static inventory files. No way to point to a custom binary as “Plugin” for dynamic inventory w/o writing a full plugin.

[shertel]

The binary itself should go in the inventory directory. The script plugin doesn’t support a YAML file.

$ ls -l inventory/
total 8
-rwxr-xr-x. 1 shertel shertel 61 Jan  3 20:41 inv.sh
-rw-r--r--. 1 shertel shertel 33 Jan  3 20:33 inv.yml

$ ansible-inventory -i inventory/ --graph
@all:
  |--@ungrouped:
  |--@test_yaml_group:
  |--@test_script_group:

[pizzapill]

Thanks @shertel I tried it and it works. I guess I go with your approach, just replacing the copied binary with a shell script that points to the binary and passes parameters.

Thanks again to everybody for your time and insights!

[shertel]

Anytime, glad that works for you. You shouldn’t actually need the indirection of calling a script to from a new script. If you don’t want to move the binary into inventory/, you could create a symlink. cd into the inventory directory and run sudo ln -s /path/to/the/binary_inv binary_inv.

-i can also be provided multiple times, so -i inventory/ -i /path/to/the/scripts/ could combine inventory sources in separate locations. The inventory sources can be configured if you don’t want to pass multiple via the CLI.

---

This is a tangent, but I just want to clarify what the YAML inventory format plugin: ns.col.plugin_name helps with. That syntax is normally parsed by the ansible.builtin.auto as a shortcut to avoid configuring additional inventory plugins. The script inventory plugin is enabled by default though, so even if the script plugin did supported parsing a YAML config file to find and run the actual script, the auto shortcut is not needed.

In the future the YAML config files will probably handle templating variables, and then I could see a case where

plugin: ansible.builtin.script
path: "{{ dynamic }}"

would make the script more dynamic. But currently the YAML config files are normally full of hardcoded options, so until then I don’t think adding YAML config support to the script inventory plugin adds any new functionality.

[bcoca (Brian Coca)]

a symliink should work just fine, no need for a wrapper

[pizzapill]

Thanks again you guys gave me a lot to consider. I was tempted by the bash file direction because there I can do other shenanigans like choosing the latest build (debug vs. release builds) etc. Stuff that concerns interactively developing the system etc.

But ansible.cfg might be a alternative to it. Thanks for your time and input!