`--no-vars` option for `ansible-inventory(1)`?

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1

Hi!

I’m using ansible-inventory --list to get a parsed view of the inventory¹.

Unfortunately, it does too much: it also outputs a huge (8 MB compared to maybe a dozen KB for the inventory) key called _meta which I have to immediately throw away again because I’m not interested.

I looked into whether I could use the Python3 API directly, but the docs say it’s internal and paws away.

So, this would not be a problem (I can just throw away that subkey)… except, to output that part, it needs the vault password.

I didn’t even notice because I have a thing that decrypts the vault password using ssh-agent automatically when needed (blogpost (in English) on that coming), but others have not yet set that up and did notice, so I added --ask-vault-pass for now.

Could please an option like --no-vars or --no-meta be added to the ansible-inventory(1) tool so that it just… doesn’t do that?

Having looked at the source, that would be an addition of… maybe three lines or so (plus indenting change).

① This is for a verification tool that checks things like, every host has exactly one host playbook xor one group playbook; every host playbook handles exactly one host; every host is in the inventory; every group playbook handles exactly one group; warn if hosts in the inventory have neither host nor group playbook; check host and group names against an RE; generate a “master playbook” that imports all others; etc. — it’s probably very specific to one certain (possibly suboptimal but historically grown) repo layout, but if there is interest, I could probably share it, I’d have to ask but experience tells me chances are good.

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(on that matter, it would be nice if the format was actually documented in the manpage and documented as stable, and if other tools outputting similar informations, like ansible-playbook --list-hosts, also had stable, documented, script-parseable output, at least with an option like --batch or so, no need to change the existing output if such an option is not given)

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How about following the basics of Unix philosophy, using one tool for one task, resulting into

ansible-inventory --inventory hosts.ini --list | jq 'del(._meta)'

and an example output of

{
  "all": {
    "children": [
      "ungrouped",
      "webservers"
    ]
  },
  "webservers": {
    "hosts": [
      "dev"
    ]
  }
}

It is also possible to remove the Default groups from the output by using

| jq 'del(._meta, .all)'

Would that be a feasible approach for you?

4

Have you considered using ansible-inventory --graph instead of --list? It does not show variables by default.

(on that matter, it would be nice if the format was actually documented in the manpage and documented as stable, …

The --list output is stable, it’s the same format emitted by inventory scripts.

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Another option is to create a Jinja2 template that dumps exactly the structure you want and run it from ansible or ansible-playbook via the template action.

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That’s what I’m doing now, as you can see from the first post, and that’s what causes the problems because it accesses the vault.

Yes. It is the very counter-example of parsable, though. Good for a human quick overview (though what is @ungrouped?).

Hmh, the --list output minus _meta is pretty much exactly what I want… and it goes to stdout instead of needing tempfiles…