Introduction

With a focus on having minimal human actions required, both in its deployment and operation, MetalK8s also intends to ease deployment and operation of complex applications, named Solutions, on its cluster.

This document defines what a Solution refers to, the responsibilities of each party in this integration, and will link to relevant documentation pages for detailed information.

What is a Solution?

We use the term Solution to describe a packaged Kubernetes application, archived as an ISO disk image, containing:

  • A set of OCI images to inject in MetalK8s image registry

  • An Operator to deploy on the cluster

  • Optionally, a UI for managing and monitoring the application, represented by a standard Kubernetes Deployment

For more details, see the following documentation pages:

Once a Solution is deployed on MetalK8s, a user can deploy one or more versions of the Solution Operator, using either the Solution UI or the Kubernetes API, into separate namespaces. Using the Operator-defined CustomResource(s), the user can then effectively deploy the application packaged in the Solution.

How is a Solution declared in MetalK8s?

MetalK8s already uses a BootstrapConfiguration object, stored in /etc/metalk8s/bootstrap.yaml, to define how the cluster should be configured from the bootstrap node, and what versions of MetalK8s are available to the cluster.

In the same vein, we want to use a SolutionsConfiguration object, stored in /etc/metalk8s/solutions.yaml, to declare which Solutions are available to the cluster, from the bootstrap node.

Todo

Add specification in a future Reference guide

Here is how it could look:

apiVersion: metalk8s.scality.com/v1alpha1
kind: SolutionsConfiguration
solutions:
  - /solutions/storage_1.0.0.iso
  - /solutions/storage_latest.iso
  - /other_solutions/computing.iso

There would be no explicit information about what an archive contains. Instead, we want the archive itself to contain such information (more details in Solution archive guidelines), and to discover it at import time.

Note that Solutions will be imported based on this file contents, i.e. the images they contain will be made available in the registry and the UI will be deployed, however deploying the Operator and subsequent application(s) is left to the user, through manual operations or the Solution UI.

Note

Removing an archive path from the solutions list will effectively remove the Solution images and UI when the “import solutions” playbook is run.

Responsibilities of each party

This section intends to define the boundaries between MetalK8s and the Solutions to integrate with, in terms of “who is doing what?”.

Note

This is still a work in progress.

MetalK8s

MUST:

  • Handle reading and mounting of the Solution ISO archive

  • Provide tooling to deploy/upgrade a Solution’s CRDs and UI

MAY:

  • Provide tooling to deploy/upgrade a Solution’s Operator

  • Provide tooling to verify signatures in a Solution ISO

  • Expose management of Solutions in its own UI

Solution

MUST:

  • Comply with the standard archive structure defined by MetalK8s

  • If providing a UI, expose management of its Operator instances

  • Handle monitoring of its own services (both Operator and application, except the UI)

SHOULD:

  • Use MetalK8s monitoring services (Prometheus and Grafana)

Note

Solutions can leverage the Prometheus Operator CRs for setting up the monitoring of their components. For more information, see Monitoring and Solution Operator guidelines.

Todo

Define how Solutions can deploy Grafana dashboards.

Interaction diagrams

We include a detailed interaction sequence diagram for describing how MetalK8s will handle user input when deploying / upgrading Solutions.

Note

Open the image in a new tab to see it in full resolution.

@startuml actor user as "User" control ui as "MetalK8s UI" control saltmaster as "Salt Master" entity bootstrap as "Bootstrap node" control apiserver as "Kubernetes API" control registry as "MetalK8s registry" == Import a new Solution (version) == user -> bootstrap : Upload Solution ISO user -> bootstrap : Add ISO path to the "SolutionsConfiguration" file user -> saltmaster ++ : Request Solutions import saltmaster <-> apiserver : Retrieve "metalk8s-solutions" ConfigMap loop For each ISO defined in "SolutionsConfiguration" saltmaster -> bootstrap ++ : Check ISO file (against our standards/constraints) ||| bootstrap --> saltmaster -- : Return status (valid or not) and metadata if any alt ISO is invalid ||| saltmaster -> saltmaster : Fail early ||| else ISO is valid ||| saltmaster -> bootstrap ++ : Run "import_solution_archive" formula ||| bootstrap -> bootstrap : Mount ISO bootstrap -> registry : Configure new ISO source ||| bootstrap -> saltmaster -- : Solution imported successfully end end loop For each latest version newly imported saltmaster <-> apiserver : Replace CRDs saltmaster <-> apiserver : Create/Update Deployment for the Solution UI end loop For each Solution version in "metalk8s-solutions" ConfigMap not in "SolutionsConfiguration" ||| saltmaster -> bootstrap ++ : Run "remove_solution_archive" formula ||| bootstrap -> registry : Remove configuration for this Solution version bootstrap -> bootstrap : Unmount ISO ||| bootstrap -> saltmaster -- : Solution removed successfully end saltmaster <-> apiserver : Update "metalk8s-solutions" ConfigMap saltmaster -> user -- : Solutions imported successfully ||| == Confirmation == user -> ui : Request Solutions listing page ui <-> apiserver : Retrieve "metalk8s-solutions" ConfigMap loop For each Solution configured ui <-> apiserver : Retrieve Solution UI Service end ui -> user : Display Solutions with the versions deployed and their UI links ||| == Deployment of the Operator == note over user Deployment of a Solution Operator should be managed in the Solution UI, allowing the user to see multiple instances of the Operator at once (different namespaces). end note opt If the user wants to perform manual deployment user -> apiserver : Create new Namespace for the Operator to manage user -> apiserver : Apply the example Deployment from the mounted Solution ISO end @enduml

Todo

A detailed diagram for Operator deployment would be useful (wait for #1060 to land). Also, add another diagram for specific operations in an upgrade scenario using two Namespaces, for staging/testing the new version.