Advanced: How Kaapana uses Helm

Note

This section is not a necessary read in order to develop workflows or applications for Kaapana. It explains the technical details of how the platform uses Helm for managing extensions.

Helm is a package manager for Kubernetes that helps define and manage different Kubernetes applications. It simplifies the deployment process by providing a templating system for writing and maintaining YAML configuration files.

For a better understanding of how Helm works, it is recommended to read the Helm documentation.

To quickly get started with Helm, refer to the Helm Quickstart Guide. Note that the server-installation-script uses snap to fetch the latest Helm version during installation.

For a detailed explanation of how to use templates in Helm, refer to Helm Chart Template Guide.

How Kaapana uses Helm charts

Kaapana uses Helm to distribute and manage Kubernetes objects. Each service, DAG and extension is a requirement of the main kaapana-admin-chart. This chart contains the fundamental features of the platform such as reverse proxy, authentication, and extension management backend.

kaapana-admin-chart chart also contains kaapana-platform-chart as one of its requirements. Most of the interactive components of Kaapana is under kaapana-platform-chart , such as Airflow, PACS, Minio, landing page and Kaapana backend. The dependency tree below shows the complete structure.

Kaapana components have different folder structures based on their type:

  1. A Kaapana extension that can be installed/uninstalled via the Extensions tab:

jupyterlab
│──── docker
      │──── Dockerfile
│──── jupyterlab-chart
      │──── templates
            │──── deployment.yaml
      │──── Chart.yaml
      │──── values.yaml

  1. A dag (Directed Acyclic Graph) that defines a set of operators in Airflow:

dags
│──── dag_collect_metadata.py

  1. A Kaapana service that provides main functionalities of the platform:

landing-page-kaapana
│──── docker
|     │──── Dockerfile
│──── landing-page-kaapana-chart
      │──── templates
      |     │──── configmap.yaml
      |     │──── deployment.yaml
      |     │──── service.yaml
      │──── Chart.yaml
      │──── values.yaml

Note

Brief explanations of different YAML files:

  • Chart.yaml is the main configuration document for Helm charts. Details for the fields can be found in the official documentation.

  • requirements.yaml is used to define the required charts for the chart to work. Running helm dep up creates a “deps” folder with the definition files of these charts.

  • values.yaml contains information that can be used in template files. Updating details in multiple Kubernetes objects becomes easier using {{ .Values.fieldName }} placeholders. More details on how to use values files can be found at helm.sh.

Useful Commands

  1. helm package . packages a chart folder into a tgz file. This can be useful for uploading tgz files into the platform using the Upload component in Extensions tab

  2. helm ls -A lists all helm releases under all namespaces. This can be used to check whether every chart is deployed or not

  3. helm ls --uninstalling --pending --failed is useful to check whether any chart is stuck in an unwanted state. Use helm uninstall -n <namespace> --no-hooks <release-name> to manually uninstall the release

  4. helm get -n <namespace> <release-name> prints the information as YAML files for all Kubernetes resources running under <release-name>

Chart Dependency Tree

kaapana-admin-chart
├── admin-namespace
├── auth-backend-chart
├── cert-init-chart
├── kaapana-admin-chart-collections
│   └── kaapana-extension-collection
│       └── sub-charts
│           ├── bodypartregression-workflow
│           ├── code-server-chart
│           ├── debug-container-chart
│           ├── federated-setup-central-test-workflow
│           ├── federated-setup-node-test-workflow
│           ├── jupyterlab-chart
│           ├── kaapana-persistence-chart
│           ├── kaapana-platform-chart
│           │   └── sub-charts
│           │       ├── extensions-namespace
│           │       ├── jobs-namespace
│           │       ├── kaapana-library-chart
│           │       └── services-namespace
│           │           └── sub-charts
│           │               ├── airflow-chart
│           │               ├── alertmanager-chart
│           │               ├── auth-backend-chart
│           │               ├── cert-copy-chart
│           │               ├── ctp-chart
│           │               ├── dcm4chee-chart
│           │               ├── dicom-init-chart
│           │               ├── grafana-chart
│           │               ├── kaapana-backend-chart
│           │               ├── kaapana-plugin-chart
│           │               ├── landing-page-kaapana-chart
│           │               ├── meta-init-chart
│           │               ├── minio-chart
│           │               ├── minio-console-chart
│           │               ├── minio-init-chart
│           │               ├── node-exporter-chart
│           │               ├── ohif-chart
│           │               ├── ohif-chart-v2
│           │               ├── ohif-iframe-chart
│           │               ├── opensearch-chart
│           │               ├── os-dashboards-chart
│           │               ├── prometheus-chart
│           │               ├── static-website-chart
│           ├── mhub-models-workflow
│           ├── mitk-flow-chart
│           ├── mitk-flow-workflow
│           ├── mitk-workbench-chart
│           ├── nnunet-federated-workflow
│           ├── nnunet-workflow
│           ├── radiomics-federated-workflow
│           ├── radiomics-workflow
│           ├── rateme-chart
│           ├── rateme-workflow
│           ├── shapemodel-workflow
│           ├── slicer-workbench-chart
│           ├── tensorboard-chart
│           └── total-segmentator-workflow
├── kaapana-library-chart
├── keycloak-chart
├── keycloak-init-chart
├── kube-dashboard-chart
├── kube-helm-chart
├── maintenance-page-chart
├── nfs-server-chart
├── oAuth2-proxy-chart
└── traefik-chart