Semantic Hub

The Semantic Hub is a logical and architectural component of Tractus-X. The source code under this folder contains reference implementations of the SLDT Semantic Hub

Build Packages

Run mvn install to run unit tests, build and install the package.

Run Package Locally

To check whether the build was successful, you can start the resulting JAR file from the build process by running java -jar target/semantic-hub-backend-{current-version}.jar.

Build Docker

Run docker build -t semantic-hub .

In case you want to publish your image into a remote container registry, apply the tag accordingly and docker push the image.

Deploy using Helm and K8s

If you have a running Kubernetes cluster available, you can deploy the Semantic Hub using our Helm Chart, which is located under ./charts/semantic-hub. In case you don't have a running cluster, you can set up one by yourself locally, using minikube. In the following, we will use a minikube cluster for reference.

Before deploying the Semantic Hub, enable a few add-ons in your minikube cluster by running the following commands:

minikube addons enable storage-provisioner

minikube addons enable default-storageclass

minikube addons enable ingress

If you want to use the in-memory triple store that is not persistent (useful for local deployments) set embeddedTripleStore: true.

In order to deploy the helm chart, first create a new namespace "semantics": kubectl create namespace semantics.

Then run helm install hub -n semantics ./charts/semantic-hub. This will set up a new helm deployment in the semantics namespace. By default, the deployment contains the Semantic Hub instance itself, and a Fuseki Triplestore.

Check that the two containers are running by calling kubectl get pod -n semantics.

To access the Semantic Hub API from the host, you need to configure the Ingress resource. By default, the Semantic Hub includes an Ingress that exposes the API on https://minikube/semantics/hub

For that to work, you need to append /etc/hosts by running echo "$(minikube ip) minikube" | sudo tee -a /etc/hosts.

For automated certificate generation, use and configure cert-manager. By default, authentication is deactivated, please adjust hub.authentication if needed

Parameters

The Helm Chart can be configured using the following parameters (incomplete list). For a full overview, please see the values.yaml.

Semantic Hub

Parameter	Description	Default value
hub.image	The registry and image of the Semantic Hub	semantic-hub:latest
hub.embeddedTripleStore	Configures whether the Semantic Hub uses its non-persistent embedded in-memory Triplestore. If set to true, no separate Fuseki instance is deployed.	false
hub.host	This value is used by the Ingress object (if enabled) to route traffic.	minikube
hub.authentication	Enables OAuth2 based authentication/authorization.	false
hub.idpIssuerUri	The issuer URI of the OAuth2 identity provider.	http://localhost:8080/auth/realms/catenax
hub.graphdbBaseUrl	The URL of an external GraphDB. Ignored if graphdb.enabled is set to false	http://graphdb:3030
hub.ingress.enabled	Configures if an Ingress resource is created.	true
hub.ingress.tls	Configures whether the Ingress should include TLS configuration. In that case, a separate Secret (as defined by hub.ingress.tlsSecretName) needs to be provided manually or by using cert-manager	true
hub.ingress.tlsSecretName	The Secret name that contains a tls.crt and tls.key entry. Subject Alternative Name must match the hub.host	hub-certificate-secret
hub.ingress.urlPrefix	The url prefix that is used by the Ingress resource to route traffic	/semantics/hub
hub.ingress.className	The Ingress class name	nginx
hub.ingress.annotations	Annotations to further configure the Ingress resource, e.g. for using with cert-manager.

GraphDB

Parameter	Description	Default value
graphdb.enabled	Configures, whether a separate Fuseki Triplestore should be deployed in the cluster.	true
graphdb.storageClassName	Defines the storage class name of the PersistentVolumeClaim that is used to persist the GraphDB data.	standard
graphdb.storageSize	Size of the PersistentVolumeClaim	50Gi