Terminology

List of Kaapana specific terms used in this guide. Note that the reader is also expected to know about containers, images and registries, which are not explained here.

  • Extension: A component that can be installed and run on the Kaapana platform. List of stable extensions can be found in the Extensions section of the documentation.

  • Application Extension: These extensions deploy standalone web applications, usually accessible via subpaths in the platform (e.g. JupyterLab, MITKWorkbench)

  • Workflow Extension: These extensions deploy workflows, which are executed via Airflow. Every processing pipeline inside Kaapana is considered a workflow (e.g. nnunet-training, totalsegmentator, collect-metadata)

  • DAG: Airflow Directed Acyclic Graph, defines a collection of operators that are executed in a specific order. Every workflow inside Kaapana defines a DAG that is managed by Airflow.

  • Operator: A single task inside a DAG. Kaapana utilizes distributed operators, where each operator is linked to a specific container that is executed in a Kubernetes pod. The scheduler of Airflow is responsible for executing the operators in the correct order.

  • Chart: A Kaapana extension is technically a Helm package which contains its configuration. It references the container images of the extension, and defines the necessary Kubernetes resources around them.

  • Microk8s: Kubernetes distribution used in Kaapana. It contains the container runtime called containerd, abbreviated as ctr, which is used to run containers inside the platform.

  • EDK: Extension Development Kit, available for versions >= 0.4.0. It provides a development environment inside Kaapana for building and deploying containers and charts. For more information Extension Development Kit (EDK)