Is it possible to define playbook-global variables in Ansible?

Question:

I have a large Ansible playbook where Docker images are built when running it. I am using an increasing number as the tag to version them. Currently, I have to specify this in every hosts: section.

I know there are global variables but from what I found by searching for “ansible” “global variables”, they have to defined outside of the playbook. Is it possible to define global variables which are global for the playbook?

Answer:

If the tag/version you are using is applicable to all hosts, then using group_vars/all is a viable option.

If the revision numbers are specific to each host entries in a host_vars/host_name file might be better.

If you want to read and initial var and then increment it after each play that becomes a bit more difficult to persist that information across plays (or each -hosts as you say) in the playbook. For example if you were looking to deploy N docker instances you might do some dynamic inventory magic like this:

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