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Binding an simple Appsody Spring boot app to DB2

This sample demonstrates binding a simple Appsody Spring boot application to DB2 in Kubernetes.

This sample makes use of Appsody for cloud-native development and deployment, it is bootstrapped into existence with Appsody, using the Appsody Spring boot stack.

Prerequisites

  • Install Appsody
brew install appsody
  • Install Appsody operator
appsody install operator

Deploying the application to Kubernetes

Appsody generates a AppsodyApplication CR called app-deploy.yaml when you run appsody build, which can be used to deploy the application to Kubernetes. In this sample we have made app-deploy.yaml available for simplicity purposes.

There are few defaults in this configuration file, that we can change or add.

  1. Application name can be changed by changing metdata.name
  2. Application image name can be changed by changing spec.applicationImage
  3. You can also add volume mounts for Kubernetes secrets acquisition by specifying the volumes and volumeMounts

More info on the parameters that can be configured in AppsodyApplication CR can be found here

Create a secret in kubernetes with DB2 credentials.

Add the DB2 credentials to db2-secret.yaml

apiVersion: v1
kind: Secret
metadata:
  name: db2-secrets
stringData:
  db2.url: <<url>>
  db2.username: <<username>>
  db2.password: <<password>>

and run

kubectl apply -f db2-secret.yaml

Deploy the application

To deploy the application to Kubernetes, run the following command

appsody deploy -t <<mynamespace>>/sample-service-binding-db2:[tag] --push

The above command performs the following actions:

  1. Calls appsody build and creates a deployment image.
  2. The -t mynamespace/myrepository[:tag] flag tags the image.
  3. The --push flag tells the Appsody CLI to push the image to Docker Hub. You can push the image to private registry by specifying --push-url and the registry url.
  4. The app-deploy.yaml file is used to issue a kubectl apply -f command against the target Kubernetes cluster.

More info on how to deploy appsody application can be found here

Testing the application

  • To determine the IP address

a. Identify the node on which your pod has been scheduled

kubectl get pods -o wide

b. Use the node name to get the IP address

kubectl get node <<nodename>> -o wide
  • To determine the mapped service port, run
kubectl get service -o wide sample-service-binding-db2
  • To access the sample application service endpoint
curl http://<<ipaddress>>:<<port>>/rest/v1/books

Service binding

This sample application acquires the Secrets via K8s volume mounts and this is done use Spring Cloud Kubernetes(SCK). Check app-deploy.yaml for info on volumes and volumeMounts.

The application enables SCK K8s Secrets mapping, and declares a set of Secrets paths, as shown here (from src/main/resources/bootstrap.yml)

spring:
  cloud:
    kubernetes:
      secrets:
        enabled: true
        paths: /etc/secrets/db2

SCK then maps the contents of each file under the directory /etc/secrets/db2 to resolve placeholders found within application.properties.

spring.datasource.url= ${db2.url}
spring.datasource.username: ${db2.username}
spring.datasource.password: ${db2.password}