Divingbell Ansible Framework¶
Ansible playbooks to achieve tasks for making bare metal changes for Divingbell target use cases.
Links¶
The work to author and implement this spec will be tracked under this Storyboard Story
Problem description¶
Divingbell uses DaemonSets and complex shell scripting to make bare metal changes. This raises 2 problems: - Increasing number of DaemonSets on each host with increasing Divingbell usecases - Reinventing the wheel by writing complex shell scripting logic to make bare metal changes.
Impacted components¶
The following Airship components will be impacted by this solution:
- Divingbell: Introducing Ansible framework to make bare metal changes
Proposed change¶
This spec intends to introduce Ansible framework within Divingbell which is much simpler to make any bare metal configuration changes as compared to existing approach of writing complex shell scripting to achieve the same functionality.
Adding playbook¶
Ansible playbooks should be written for making any configuration changes on the host.
Existing shell script logic for making bare metal changes lives under
divingbell/templates/bin
, wherever applicable these should be replaced
by newly written Ansible playbooks as described in the sections below.
Ansible playbooks would be part of the Divingbell image.
A separate directory structure needs to be created for adding the playbooks. Each Divingbell config can be a separate role within the playbook structure.
- playbooks/
- roles/
- systcl/
- limits/
- group_vars
- all
- master.yml
Files under group_vars
should be loaded as a Kubernetes ConfigMap
or
Secret
inside the container. Existing entries in values.yaml
for
Divingbell should be used for populating the entries in the file under
group_vars
.
This PS Initial commit for Ansible framework should be used as a reference PS for implementing the Ansibile framework.
Ansible Host¶
With Divingbell DaemonSet running on each host mounted at hostPath
,
hosts
should be defined as given below within the master.yml
.
hosts: all
connection: chroot
Ansible chroot plugin should be used for making host level changes. Ansible chroot plugin_
Divingbell Image¶
Dockerfile should be created containing the below steps:
- Pull base image
- Install Ansible
- Define working directory
- Copy the playbooks to the working directory
Divingbell DaemonSets¶
All the Divingbell DaemonSets that follow declarative and idempotent models
should be replaced with a single DaemonSet. This DaemonSet will be
responsible for populating required entries in group_vars
as
volumeMounts
. Ansible command to run the playbook should be invoked from
within the DaemonSet
spec.
The Ansible command to run the playbook should be invoked from within
the DaemonSet
spec.
The Divingbell DaemonSet for exec
module should be left out from this framework
and it should keep functioning as a separate DaemonSet.
Ansible Rollback¶
Rollback should be achieved via the update_site
action i.e. if a playbook
introduces a bad change into the environment then the recovery path would be to
correct the change in the playbooks and run update_site
with new changes.
Security impact¶
None - No new security impacts are introduced with this design.
Performance impact¶
As this design reduces the number of DaemonSets being used within Divingbell, it will be an improvement in performance.
Implementation¶
This implementation should start off as a separate entity and not make parallel changes by removing the existing functonality.
New Divingbell usecases can be first targetted with the Ansible framework while existing framework can co-exist with the new framework.
Dependencies¶
Adds new dependency - Ansible framework.