Using direct secret references

In this Services Toolkit tutorial you learn how developers can use direct references to Kubernetes Secret resources to connect their application workloads to almost any backing service.

This includes backing services that:

• Run external to Tanzu Application Platform
• Do not adhere to ProvisionedService in the Service Binding Specification for Kubernetes in GitHub.

If you are familiar with Cloud Foundry and Tanzu Application Service, this capability is similar to the concept of user-provided service instances. For more information about user-provided service instances in Cloud Foundry, see the Cloud Foundry documentation.

This tutorial demonstrates a procedure to bind a new application on Tanzu Application Platform to an existing PostgreSQL database that exists in Azure. However, the steps are applicable to any backing service that you want to connect to.

About this tutorial

Target user role: Service Operator and Application Operator
Complexity: Easy
Estimated time: 10 minutes
Topics covered: Service Binding, Direct Secret References
Learning outcomes: Ability to bind workloads to almost any backing service using direct secret references

Prerequisites

Before you can follow this tutorial, you must have:

• Access to a Tanzu Application Platform cluster v1.5.0 or later.
• An Azure PostgreSQL database to connect to.
• Configured networking between the workload and the service endpoint and you must have the credentials for the backing service. Whether this requires extra steps depends on your Kubernetes distribution and the backing service you want to connect your Tanzu Application Platform workloads to.

Create a binding-compatible secret

1. Create a file named external-azure-db-binding-compatible.yaml and enter a Kubernetes secret resource similar to the following example:

   # external-azure-db-binding-compatible.yaml
   ---
   apiVersion: v1
   kind: Secret
   metadata:
     name: external-azure-db-binding-compatible
   type: Opaque
   stringData:
     type: postgresql
     provider: azure
     host: EXAMPLE.DATABASE.AZURE.COM
     port: "5432"
     database: "EXAMPLE-DB-NAME"
     username: "USER@EXAMPLE"
     password: "PASSWORD"
   

   Substitute in the values as required.

   When using direct secret references, the Secret values must abide by the Well-known Secret Entries specifications as defined by the Service Binding Specification for Kubernetes. If you plan to bind this secret to a Spring-based application workload and want to take advantage of the auto-wiring feature, this secret must also contain the properties required by Spring Cloud Bindings.

2. Apply the YAML file by running:

   kubectl apply -f external-azure-db-binding-compatible.yaml
   

3. In a file named stk-secret-reader.yaml, grant sufficient Role-Based Access Control (RBAC) permissions to permit Services Toolkit to read the secrets specified by the class:

   # stk-secret-reader.yaml
   ---
   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRole
   metadata:
     name: stk-secret-reader
     labels:
       servicebinding.io/controller: "true"
   rules:
   - apiGroups:
     - ""
     resources:
     - secrets
     verbs:
     - get
     - list
     - watch
   

4. Apply your changes by running:

   kubectl apply -f stk-secret-reader.yaml
   

5. Create a claim for the newly created secret by running:

   tanzu service resource-claim create external-azure-db-claim \
     --resource-name external-azure-db-binding-compatible \
     --resource-kind Secret \
     --resource-api-version v1
   

6. Obtain the claim reference of the claim by running:

   tanzu service resource-claim list -o wide
   

   Expect to see the following output:

   NAME                     READY  REASON  CLAIM REF
   external-azure-db-claim  True           services.apps.tanzu.vmware.com/v1alpha1:ResourceClaim:external-azure-db-claim
   

   From the output, record the value of CLAIM REF.

7. Create an application workload by running a command similar to the following example:

   tanzu apps workload create WORKLOAD-NAME \
     --git-repo https://github.com/sample-accelerators/spring-petclinic \
     --git-branch main \
     --git-tag tap-1.2 \
     --type web \
     --label app.kubernetes.io/part-of=spring-petclinic \
     --annotation autoscaling.knative.dev/minScale=1 \
     --env SPRING_PROFILES_ACTIVE=postgres \
     --service-ref db=REFERENCE
   

   Where:

   • WORKLOAD-NAME is the name of the application workload. For example, pet-clinic.
   • REFERENCE is the value of the CLAIM REF for the newly created claim in the output of the last step.