"hash_behaviour = merge" issue

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1

Hi,

I would like to build up a variable from defaults, group_vars and host_vars - but hash_behaviour doesn’t seem to be working as I’d expect it to.

The plan is to have a default config (in this case haproxy) and then allow additional frontends to be defined at group and host_var level.

I’ve created a very simple example which hopefully explains the issue:

https://github.com/tdac/Ansible-HashMerge-Issue

I’m wondering if the “-” notation in the inventory stops Ansible seeing this as mergable?

Thanks in advance for any pointers you can give me!

Tim

2

What you have is a list not a hash aka dictionary.
The documentation says it only works on hash/dictionary so I guess thats why.

3

Thanks Kai,

That would explain it - is there a ‘standard’ way of merging a list in this context?

Tim

4

Standard in what situation?
List is usually used in a loop, and the with_items can have several entries so you'll have a merge there.

with_items:
   - haproxy_frontend_host | default()
   - haproxy_frontend_group | default()

5

Hi Kai,

Thanks - so if I’ve understood correctly - I could set:

haproxy_frontend_group:

  • name: http

in group_vars

and

haproxy_frontend_host:

  • name: https

and then use your ‘with items’ suggestion to combine them…I suppose my dream was to have list variables that work like hashes do. For example If one defines a default configuration for a group of servers in group_vars - and then want to add ‘special cases’ at host_vars level - that’s currently not possible with lists (which is a shame - as lists offer a richer way to define services I think?).

Is there a theoretical reason why lists can’t be merged the same way as hashes?

Tim

6

Yes, but I forgot the curly brackets, it should be.

   with_items:
   - '{{ haproxy_frontend_host | default() }}'
   - '{{ haproxy_frontend_group | default() }}'