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

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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

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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

[esco real]

If someone is interested in this topic:

Now, I use the name and the UUID of the groups (name_uuid) to build up the tree (children, group_vars..). So group names don't have to be unique and performance and scaling isn't a problem anymore..

If you use a CMDB your groups usually would have some IDs, too.

esco

[Krzysztof Zarzycki]

If someone come up with a solution (like a dynamic inventory script that reads some inverted inventory dsl), please share, I would be very interested! 
I see the need for such inverted inventory in the case, where I have a lot of interconnected services, where number of services is really large. This is how hadoop environment looks like with tens of different services.

Thanks,

Krzysztof