Hi All,
I've been trying to work out the best layout for our playbooks and roles.
I've been attempting to conform to DRY principles but trying to leave
things as loosely coupled as possible.
Our infrastructure involves many similar apps that have minor differences
which is why I've been looking specifically at how it might be possible to
parameterise playbooks/roles to avoid many very similar files.
Initially I had something like this:
## apps described in 'meta roles' (roles with only meta/main.yml that
include other roles)
# app1.yml
roles:
- app1
# app2.yml
roles:
- app2
# roles/app1/meta/main.yml
dependencies:
- { role: pre_deploy_common_stuff }
- { role: deploy_app_1 }
- { role: deploy_other_stuff }
- { role: post_deploy_common_stuff }
# roles/app2/meta/main.yml
dependencies:
- { role: pre_deploy_common_stuff }
- { role: deploy_app_2 }
- { role: post_deploy_common_stuff }
## ---
Then I tried moving the contents of 'meta/main.yml' for each app into
playbooks like this:
## apps described in playbooks
# app1.yml
- roles:
- { role: pre_deploy_common_stuff }
- { role: deploy_app_1 }
- { role: deploy_other_stuff }
- { role: post_deploy_common_stuff }
# app2.yml
- roles:
- { role: pre_deploy_common_stuff }
- { role: deploy_app_2 }
- { role: post_deploy_common_stuff }
## ---
Then thinking in DRY terms, I tried this:
## templated playbook with parameterization
# app1.yml
- vars:
my_roles:
- { role: deploy_app_1 }
- { role: deploy_other_stuff }
include: foo.yml my_roles="{{ my_roles }}"
# app2.yml
- vars:
my_roles:
- { role: deploy_app_2 }
include: foo.yml my_roles="{{ my_roles }}"
# foo.yml
- roles:
- { role: pre_deploy_common_stuff }
# this won't work because 'roles' expects a list but gets string 'my_roles'
- roles: "{{ my_roles }}"
# neither will this because with_items doesn't work in playbooks
- roles: "{{ item }}"
with_items: my_roles # or "{{ my_roles }}"
# 'role' is equivalent to including various main.yml files manually.
# we still can't use with_items or pass a list as a single argument to
include so
# using include: in place of role: wouldn't work either
- roles:
- { role: post_deploy_common_stuff }
# a possibility would be to test with_items in a meta/main.yml file but
# at that point we're moving back towards 'meta role' territory..!
## --
The last example doesn't work for reasons described in the comments. I had
a quick and nasty go at getting ansible 'roles:' to allow lists or
with_items but to no avail.
I think the last pattern may work in a 'meta' style role (rather than
playbook) but I'm hesitant to introduce this concept of meta-roles when it
seems like that information should be stored in playbooks.
I'd be interested to hear how other people approach this type of
configuration or whether I've made any mistakes in my understanding of how
to write playbooks/roles.
Thanks!
Rob
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