how to filter out specific AWS rds instances which have specific tags using ansible

Question

I am trying to list all the AWS RDS instances which have my cusotm tag defined using ansible playbooks, I am using the rds_instance_info to get the data of all the rds instances.

    - name: List RDS instances
      hosts: localhost
      tasks:
        - name: Get RDS instance info
          amazon.aws.rds_instance_info:
            region: xx-xxxx-x
            aws_access_key: xxxxxxxxxxxxxxxx
            aws_secret_key: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
          register: rds_info
    
        - set_fact:
            var: "{{ rds_info.instances | selectattr('tags', 'defined') | selectattr('tags.stack', 'equalto', 'custom-tag-value') | default([]) | list }}"
          loop: "{{ rds_info.instances }}"

        - debug:
            msg: "{{ item.db_instance_identifier }}"
          loop: "{{ var }}"

The error i get is,

{"msg": "The task includes an option with an undefined variable. The error was: 'dict object' has no attribute 'stack'. 'dict object' has no attribute 'stack'

Not all instances have tags defined and the ones having tags defined don't always have the tag "stack".

Answer 1

Q: "List all instances which have my custom tag defined."

A: Use json_query. For example, given the data for testing

    rds_info:
      instances:
        - name: A
          tags: {stack: custom-tag-name, tag: tag_A}
        - name: B
          tags: {tag: tag_B}
        - name: C
        - name: D
          tags: {stack: X, tag: tag_D}

Declare the list of "instances which have my custom tag defined"

    result: "{{ rds_info.instances|json_query(result_query) }}"
    result_query: '[?tags.stack == `custom-tag-name`]'

gives

  result:
  - name: A
    tags:
      stack: custom-tag-name
      tag: tag_A

---

Example of a complete playbook for testing

- hosts: localhost

  vars:

    # Not all instances have tags defined and the ones having tags defined
    # don't always have the tag 'stack'

    rds_info:
      instances:
        - name: A
          tags: {stack: custom-tag-name, tag: tag_A}
        - name: B
          tags: {tag: tag_B}
        - name: C
        - name: D
          tags: {stack: X, tag: tag_D}


    result: "{{ rds_info.instances|json_query(result_query) }}"
    result_query: '[?tags.stack == `custom-tag-name`]'

#    result: "{{ rds_info.instances|
#                selectattr('tags', 'defined')|
#                selectattr('tags.stack', 'equalto', 'custom-tag-name') }}"
#
#    result: 'VARIABLE IS NOT DEFINED!: ''dict object'' has no attribute ''stack''

  tasks:

    - debug:
        var: result