Module defaults

If you find yourself calling the same module repeatedly with the same arguments, it can be useful to define default arguments for that particular module using the module_defaults attribute.

Here is a basic example:

- hosts: localhost
  module_defaults:
    file:
      owner: root
      group: root
      mode: 0755
  tasks:
    - file:
        state: touch
        path: /tmp/file1
    - file:
        state: touch
        path: /tmp/file2
    - file:
        state: touch
        path: /tmp/file3

The module_defaults attribute can be used at the play, block, and task level. Any module arguments explicitly specified in a task will override any established default for that module argument:

- block:
    - debug:
        msg: "a different message"
  module_defaults:
    debug:
      msg: "a default message"

It’s also possible to remove any previously established defaults for a module by specifying an empty dict:

- file:
    state: touch
    path: /tmp/file1
  module_defaults:
    file: {}

Here are some more realistic use cases for this feature.

Interacting with an API that requires auth:

- hosts: localhost
  module_defaults:
    uri:
      force_basic_auth: true
      user: some_user
      password: some_password
  tasks:
    - uri:
        url: http://some.api.host/v1/whatever1
    - uri:
        url: http://some.api.host/v1/whatever2
    - uri:
        url: http://some.api.host/v1/whatever3

Setting a default AWS region for specific EC2-related modules:

- hosts: localhost
  vars:
    my_region: us-west-2
  module_defaults:
    ec2:
      region: '{{ my_region }}'
    ec2_instance_facts:
      region: '{{ my_region }}'
    ec2_vpc_net_facts:
      region: '{{ my_region }}'

Module defaults groups

Ansible 2.7 adds a preview-status feature to group together modules that share common sets of parameters. This makes it easier to author playbooks making heavy use of API-based modules such as cloud modules.

Group	Purpose	Ansible Version
aws	Amazon Web Services	2.7
azure	Azure	2.7
gcp	Google Cloud Platform	2.7
k8s	Kubernetes	2.8
os	OpenStack	2.8

Use the groups with module_defaults by prefixing the group name with group/ - e.g. group/aws

In a playbook, you can set module defaults for whole groups of modules, such as setting a common AWS region.

# example_play.yml
- hosts: localhost
  module_defaults:
    group/aws:
      region: us-west-2
  tasks:
  - aws_s3_bucket_facts:
  # now the region is shared between both facts modules
  - ec2_ami_facts:
      filters:
        name: 'RHEL*7.5*'