helm diff output

[krisek]

SUMMARY

The Kubernetes returns with --check --diff CLI parameters, the actual diff that would be applied on the cluster. It would be great if the helm module would do the same.

ISSUE TYPE

• Feature

COMPONENT NAME

helm.py

ADDITIONAL INFORMATION

It would be a great enhancement for CI/CD pipelines.

ansible-playbook -i inventory.yaml  -e variable_host="play" --check --diff basic-service-deploy.yaml

  - name: install helm package
    kubernetes.core.helm:
      chart_ref: "{{ chart_ref }}"
      chart_version: "{{ version }}"
      create_namespace: y
      context: "{{ inventory_hostname }}"
      release_name: hello
      release_namespace: hello-world
      release_state: present

[abikouo]

Hi @krisek

Thanks for taking the time to report this feature. helm module does not support the diff mode for now, but this is a feature we may need to address later.

[gravesm]

To clarify, a diff is currently returned if you are upgrading an existing release and you have the helm diff plugin installed. We do not generate a diff if you are installing a new release or if you do not have helm diff installed. I think we should be able to easily add the diff for installing new releases as this is supported by helm diff. I would not see us adding diff support without helm diff installed in the near future, though, as this would be a significant amount of effort.

[krisek]

Yes, without helm diff it is definitely a mission impossible. The background is that I'm working on a CI/CD pipeline that has a dry-run feature -- to help the operator to see what would happen if the pipeline were really ran.

[pauvos]

@krisek , you can achieve something like this by comparing the current and future release with helm_template and fact_diff.

Pseudo code:

- name: "{{ release_name }} : fetch existing release info"
  kubernetes.core.helm_info:
    release_name: "{{ release_name }}"
    release_namespace: "{{ release_namespace }}"
  check_mode: false
  changed_when: false
  when: ansible_diff_mode
  register: existing_info

- name: "{{ release_name }} : render existing release"
  kubernetes.core.helm_template:
    chart_version: "{{ existing_info['status']['chart'][(chart_name|length + 1):] }}" # cut version from "somechart-1.2.3"
    release_values: "{{ existing_info['status']['values'] }}" # use values from last release
    validate: true # opened pull request #587 for this one
    ...
  ...
  register: existing_tpl

- name: "{{ release_name }} : render new release"
  kubernetes.core.helm_template:
    chart_version: "{{ new_version }}"
    release_values "{{ new_release_values }}"
    ...
  ...
  register: new_tpl

- name: "{{ release_name }} : diff"
  ansible.utils.fact_diff: 
    before: "{{ existing_tpl.stdout|default('')|trim }}"
    after: "{{ new_tpl.stdout|trim }}"
  ...
  changed_when: existing_tpl.stdout|default('')|trim != new_tpl.stdout|trim

fact_diff produces less verbose (only a few lines of changes) and more readable (green/red diff lines) output than running kubernetes.core.helm in diff_mode. If no current release exists, all new manifests will be displayed.

Pull request for --validate: #587