Inheritance of variables .. host_vars, group_vars .. a question

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1

Hello,

I’ve got a big problem with host and group variables in my playbook and Im not
sure if I am just plain stupid or if I am running into a bug or am abusing
ansible in some kind :wink:

Some background, I use ansible 1.9.4 installed from brew on OS X.

I have a group of currently two servers and I would like to configure mariadb
service. As I have lots of parameters for mariadb I tried to split them into
parameters for both servers and put them into a group variable file and those
exclusive for the single instance are in the host_vars config file:

#> grep -A 3 mariadb group_vars/api.yaml
mariadb:
version: 10.0
query_cache_size: 67108864
log_bin_dir: mariadb-binlogs

#> grep -A 2 mariadb host_vars/api02.yaml
mariadb:
server_id: 102
is_master: false

What I expected to happen, was that both arrays will be merged when I run the
playbook, but instead my playbook bailes out with an missing variable error.
First I thought ansible would miss the group of my server, but variables from
the all.yaml group file are being loaded.

Using “debug: var=mariadb” I verified the content of the mariadb array to this:
TASK: [mariadb | debug var=mariadb] *******************************************
ok: [api02] => {
“var”: {
“mariadb”: {
“is_master”: false,
“server_id”: 102
}
}
}

So, as I learned, the mariadb array from the group_vars file got replaced by
the one from the host_vars file. I guess my expectation that those arrays would
be merged into one large array is plain wrong or did I trigger a bug?

Any ideas on how to to achieve the merge behaviour? It would save me a lot of
typing and variable duplication if the arrays would be merged instead of being
replaced… with two database servers in the group its ok, but if I have to
configure larger groups with for example a dozen servers I would have to copy
over the whole array.

Greets,
Marcus

2

this is the default behaviour, ansible overwrites vars when there is a
conflict, the most specific one or last loaded wins.

in ansible.cfg the 'hash_behaviour' setting can change this, switch
the value from the default 'replace' to 'merge'.

3

Thanks for the quick answer, this is great to know!

Sorry for sending the mail three times, my mail client reported an error when sending.

Greetings,
Marcus