[ansible-project] tree/hierarchic structure for inventory?

[esco real]

Hello,

I would like to discuss the idea for a hierarchic structure for the
inventory. Would it possible to support something like that?

For example with this structure:

| server
| -- atlanta
| `-- web
| `--hosts:web1
| -- raleigh
| `-- web
| `-- host:web2

You would need this config:
{
"web" : { "hosts": [ "web1", "web2" ] },
"server" : { "hosts": [ "web1", "web2" ] },
"atlanta" : { "hosts": [ "web1" ] },
"raleigh" : { "hosts": [ "web2" ] }
}


To work with "children" the group names would have to be unique in the
whole tree. So "web" would break this up.

Wouldn't it be nice to use something like that?
{
"server"
{ "atlanta" { "web" {"hosts": [ "web1" ] } } },
{ "raleigh" { "web" {"hosts": [ "web2" ] } } }
}

I came up with this by using a KeePass database as inventory source:
https://github.com/escoreal/ansible_kdb_inventory
Here I have to build the tree for each host and add it to all parents. But
this doesn't scale to well.

Thanks,
esco

[Mischa ter Smitten]

We are working on the same problem. Right know we are using a custom piece of python code with nested dicts to represent our group and return them as json.

[Paul Markham]

You can write a dynamic inventory script which allows you to specify the
inventory in another format, or fetch it from a configuration management
database.

I'm not sure if this is exactly what you want, but I wrote one that lets
you specify servers and which parent groups they belong in; basically the
inverse of the normal inventory. The code is
here https://github.com/pmarkham/ansible-inventory-inverted.

[esco real]

Hello Paul,

yes, I did likely the same but used a KeePass 2 database instead of an ini
file as inventory source. So here we have similar thoughts (if you are
using KeePass 2 you should try my script ;) ). Adding each host to his
parents is possible. But apart from the scaling problem you would have
trouble with group_vars for non unique group names in different branches.
And I guess there are a lot more users which manage their inventory as tree.

esco

[Martin]

Hi Paul,

I think the inverted inventory is a *great idea*.

IIRC clusterssh went from a format that was similiar to the "normal"
ansible inventory to something like this:

node1 group1,group2,group3
node2 group3
node3 group1,group3

I think that this is a more natural way of specifying it rather than the
sectioning of ini files. The group_vars/group1, group_vars/group2, ...
files (or dirs) could be used to specify common attributes, the dynamic
inventory script could read these and output just the right information :)

Of course this create yet another config file format but that is just
because I'm comparing to a tool where I found the inventory management to
be somewhat working. When dealing with manual inventory management (of
course going for larger numbers of servers nothing beats an actuall
automated inventory) :)

/Martin

Post by esco real
Hello Paul,
yes, I did likely the same but used a KeePass 2 database instead of an ini
file as inventory source. So here we have similar thoughts (if you are
using KeePass 2 you should try my script ;) ). Adding each host to his
parents is possible. But apart from the scaling problem you would have
trouble with group_vars for non unique group names in different branches.
And I guess there are a lot more users which manage their inventory as tree.
esco
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[Paul Markham]

Hi Martin,

I originally had the inventory in yaml format, but changed to ini format
for some reason (which I can't remember). The clusterssh format would work
well if you just wanted the host and group relationships, but I also wanted
to support host and group variables like the default static inventory
format does.

Ideally a CMDB of some sort would be used, but we don't have one so we need
to maintain a manual inventory.

Fortunately they've made it flexible enough to support whatever format you
want to use; I'm currently playing with getting the inventory from etcd so
we can dynamically add and remove hosts.

[esco real]

Hello,

to build a tree with ini format I think something like that could be used:

[server.atlanta.web]
web1

[server.raleigh.web]
web2

esco

[Martin]

Hi,

yes the host and group variables are the most important thing and I'd
personally go and separate them out to the group_vars/.... and
host_vars/.... directories. That is just a matter preference.

I have no emotional attachement to the the file format. I'm just saying
that I saw this format working and it was working very convenient to work
with.

I think a large part of the way will be discussing this as it is nearly
infinitely more complicated to create something that is then very simple to
use :)

/Martin

Post by esco real
Hello,
[server.atlanta.web]
web1
[server.raleigh.web]
web2
esco
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[esco real]

Hello Martin,

you are right. Supporting a tree structure for this with plain
files/directories (group_vars..) wouldn't be that nice. And it is very
sensible at the moment.

But I made this work for me by resolving the group_vars in the tree
directly to host_vars. So group names don't have to be unique in the
inventory. And now I am very happy with the combination of Ansible and
KeePass..

esco