host variables in hosts file versus host variables in files within host_vars inventory directory

[Jason S]

The inventory documentation describes setting some variables for a single host in a hosts file

http://docs.ansible.com/ansible/latest/intro_inventory.html#host-variables

[atlanta]
host1 http_port=80 maxRequestsPerChild=808
host2 http_port=303 maxRequestsPerChild=909

Continuing with that example, how do you access the variable?

If I use

   hostvars[inventory_hostname]['{{ inventory_hostname }} http_port']

the value I get is 

    80 maxRequestsPerChild=808
and I'd have to do some further splitting of the string to get the values.

Otherwise I can use a new line, but the example in Ansible docs puts them on one line, so I was curious as to how to access them simply.

If, however I use an inventory structure such as

-- inventories

   |-- group_vars

   |   |-- atlanta 

   |-- host_vars

   |   |-- host1

   |   |-- host2

   |-- hosts

And in the host1 file I have

http_port: 80

maxRequestsPerChild: 808

Then I can access the variable values with

hostvars[inventory_hostname]['http_port']

hostvars[inventory_hostname]['maxRequestsPerChild']

The questions are then

1. How do I access the variables as in the first example of host variables in the hosts file as described at http://docs.ansible.com/ansible/latest/intro_inventory.html#host-variables ?

2. Why are the variables not consistent whether defined in a host file or host_vars subdirectory? Is this intentional?

[Brian Coca]

I'm not sure where you got `hostvars[inventory_hostname]['{{
inventory_hostname }} http_port']` but that does not look like a valid
construct

In any case, using:

hostvars[inventory_hostname]['http_port']
hostvars[inventory_hostname]['maxRequestsPerChild']

you should be able to access the vars no matter if defined inline in
the inventory or in a host/group-vars file,
but just use `http_port` and `maxRequestsPerChild` directly, you
really only need hostvars when accessing other hosts or trying to
compose variable names.

--
----------
Brian Coca

[Jason S]

Hi Brian,

I got that via trial and error

I'm using ansible 2.4.2.0

In my case I have an inventory setup like this

inventories/uat/hosts

inventories/uat/host_vars/stable-1

inventories/uat/host_vars/stable-2

inventories/uat/group_vars/stable

in inventories/uat/hosts

[stable]

stable-1

stable-2

[stable:vars]

stable-1 http_port=80 maxRequestsPerChild=808

stable-2 http_port=303 maxRequestsPerChild=909

If I run a simply play-book like this

---

- hosts: stable-1

  connection: ssh

  gather_facts: no

  tasks:

    - name: Debug http_port

      debug:

        var: hostvars[inventory_hostname]['http_port']

    - name: Debug http_port

      debug:

        var: hostvars[inventory_hostname][inventory_hostname + ' http_port']

    - name: Debug maxRequestsPerChild

      debug:

        var: hostvars[inventory_hostname]['maxRequestsPerChild']

I get

stable-1 | SUCCESS => {

    "changed": false, 

    "hostvars[inventory_hostname]['http_port']": "VARIABLE IS NOT DEFINED!"

}

stable-1 | SUCCESS => {

    "changed": false, 

    "hostvars[inventory_hostname][inventory_hostname + ' http_port']": "80 maxRequestsPerChild=808"

}

stable-1 | SUCCESS => {

    "changed": false, 

    "hostvars[inventory_hostname]['maxRequestsPerChild']": "VARIABLE IS NOT DEFINED!"

}

If I define the host variables in inventories/uat/host_vars/stable-1 then it works as expected (i.e variable values available via hostvars[inventory_hostname]['http_port'] )

[Jason S]

I should have mentioned I have inventory = inventories/uat defined in my ansible.cfg or I'm running the playbook with -i inventories/uat  (or both)

[Brian Coca]

[stable:vars]
stable-1 http_port=80 maxRequestsPerChild=808

^ this is defining a var named 'stable-1 http_port' , not http_port for stable-1
the format is:

[groupname:vars]
varname=value


then you can use simply with:

debug:
var: varname

or

debug:
var: hostvars[inventory_hostname]['varname']


If you want to define a variable PER host do it in the host definition
[groupname]
hostname varname=value

--
----------
Brian Coca

[Jason S]

Ah, thank-you Brian.

Now I have the variables next to the host definition (within the group definition) it works fine, as expected.

I'm trying to think why I missed this even though it was staring me in the face on the documentation page.

I guess I was thinking that all variables would have to be defined with [:vars]

I had actually tried

[stable-1:vars]

var=value

that is

[hostname:vars]

var=value

And if you can do

[groupname]

hostname var=value

Why not

[groupname]

groupvar=groupvalue

groupvar2=groupvalue2

hostname var1=value1 var2=value2

Anyway it is all working for me now so thanks again.