Chapter 11. Integrating Spring Boot with Kubernetes

Procedure

1. Enable the Kubernetes integration by adding the following Maven dependency to the pom.xml file of your Spring Boot Maven project.

   <project ...>
     ...
     <dependencies>
       ...
       <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-kubernetes-config</artifactId>
       </dependency>
       ...
     </dependencies>
     ...
   </project>

2. To complete the integration,

   • Add some annotations to your Java source code
   • Create a Kubernetes ConfigMap object
   • Modify the OpenShift service account permissions to allow your application to read the ConfigMap object.

Procedure

1. Open a new shell prompt and enter the following Maven command to create a simple Camel Spring Boot project.

   mvn org.apache.maven.plugins:maven-archetype-plugin:2.4:generate \
     -DarchetypeCatalog=https://maven.repository.redhat.com/ga/io/fabric8/archetypes/archetypes-catalog/2.2.0.fuse-sb2-780040-redhat-00002/archetypes-catalog-2.2.0.fuse-sb2-780040-redhat-00002-archetype-catalog.xml \
     -DarchetypeGroupId=org.jboss.fuse.fis.archetypes \
     -DarchetypeArtifactId=spring-boot-camel-config-archetype \
     -DarchetypeVersion=2.2.0.fuse-sb2-780040-redhat-00002

   The archetype plug-in switches to interactive mode to prompt you for the remaining fields:

   Define value for property 'groupId': : org.example.fis
   Define value for property 'artifactId': : fuse78-configmap
   Define value for property 'version':  1.0-SNAPSHOT: :
   Define value for property 'package':  org.example.fis: :
   Confirm properties configuration:
   groupId: org.example.fis
   artifactId: fuse78-configmap
   version: 1.0-SNAPSHOT
   package: org.example.fis
   Y: : Y

   When prompted, enter org.example.fis for the groupId value and fuse78-configmap for the artifactId value. Accept the defaults for the remaining fields.

2. Log in to OpenShift and switch to the OpenShift project where you will deploy your application. For example, to log in as the developer user and deploy to the openshift project, enter the following commands:

   oc login -u developer -p developer
   oc project openshift

3. At the command line, change to the directory of the new fuse78-configmap project and create the Secret object for this application.

   cd fuse78-configmap
   oc create -f sample-secret.yml

   Note

   It is necessary to create the Secret object before you deploy the application, otherwise the deployed container enters a wait state until the Secret becomes available. If you subsequently create the Secret, the container will come out of the wait state. For more information on how to set up Secret Object, see Setting up Secret.

4. Build and deploy the quickstart application. From the top level of the fuse78-configmap project, enter:

   mvn fabric8:deploy -Popenshift

5. View the application log as follows.

   1. Navigate to the OpenShift web console in your browser (https://OPENSHIFT_IP_ADDR, replace OPENSHIFT_IP_ADDR with the IP address of the cluster) and log in to the console with your credentials (for example, with username developer and password, developer).
   2. In the left hand side panel, expand Home. Click Status to view the Project Status page. All the existing applications in the selected namespace (for example, openshift) are displayed.
   3. Click fuse78-configmap to view the Overview information page for the quickstart.
   4. In the left hand side panel, expand Workloads.
   5. Click Pods and then click fuse78-configmap-xxxx. The pod details for the application are displayed.
   6. Click on the Logs tab to view the application logs.

6. The default recipient list, which is configured in src/main/resources/application.properties, sends the generated messages to two dummy endpoints: direct:async-queue and direct:file. This causes messages like the following to be written to the application log:

   5:44:57.377 [Camel (camel) thread #0 - timer://order] INFO  generate-order-route - Generating message message-44, sending to the recipient list
   15:44:57.378 [Camel (camel) thread #0 - timer://order] INFO  target-route-queue - ----> message-44 pushed to an async queue (simulation)
   15:44:57.379 [Camel (camel) thread #0 - timer://order] INFO  target-route-queue - ----> Using username 'myuser' for the async queue
   15:44:57.380 [Camel (camel) thread #0 - timer://order] INFO  target-route--file - ----> message-44 written to a file

7. Before you can update the configuration of the fuse78-configmap application using a ConfigMap object, you must give the fuse78-configmap application permission to view data from the OpenShift ApiServer. Enter the following command to give the view permission to the fuse78-configmap application’s service account:

   oc policy add-role-to-user view system:serviceaccount:openshift:qs-camel-config

   Note

   A service account is specified using the syntax system:serviceaccount:PROJECT_NAME:SERVICE_ACCOUNT_NAME. The fis-config deployment descriptor defines the SERVICE_ACCOUNT_NAME to be qs-camel-config.

8. To see the live reload feature in action, create a ConfigMap object as follows:

   oc create -f sample-configmap.yml

   The new ConfigMap overrides the recipient list of the Camel route in the running application, configuring it to send the generated messages to three dummy endpoints: direct:async-queue, direct:file, and direct:mail. For more information about ConfigMap object, see Setting up ConfigMap. This causes messages like the following to be written to the application log:

   16:25:24.121 [Camel (camel) thread #0 - timer://order] INFO  generate-order-route - Generating message message-9, sending to the recipient list
   16:25:24.124 [Camel (camel) thread #0 - timer://order] INFO  target-route-queue - ----> message-9 pushed to an async queue (simulation)
   16:25:24.125 [Camel (camel) thread #0 - timer://order] INFO  target-route-queue - ----> Using username 'myuser' for the async queue
   16:25:24.125 [Camel (camel) thread #0 - timer://order] INFO  target-route--file - ----> message-9 written to a file (simulation)
   16:25:24.126 [Camel (camel) thread #0 - timer://order] INFO  target-route--mail - ----> message-9 sent via mail

1. Create a Sample Secret Object
2. Configure volume mount for the Secret
3. Configure spring-cloud-kubernetes to read Secret properties

Procedure

1. In your Spring Boot application, use the externalized configuration mechanism to access the ConfigMap property source. For example, by annotating a Java bean with the @Configuration annotation, it becomes possible for the bean’s property values to be injected by a ConfigMap.
2. In your project’s bootstrap.properties file (or bootstrap.yaml file), set the spring.application.name property to match the name of the ConfigMap.

3. Enable the view permission on the service account that is associated with your application (by default, this would be the service account called default). For example, to add the view permission to the default service account:

   oc policy add-role-to-user view system:serviceaccount:$(oc project -q):default -n $(oc project -q)

Procedure

1. Navigate to src/main/resources directory of the quickstart project and open the bootstrap.yml file.
2. Change the configuration property spring.cloud.kubernetes.reload.enabled=true.

Procedure

1. Assume that the reload feature is enabled with default settings (refresh mode). The following bean will be refreshed when the config map changes:

   @Configuration
   @ConfigurationProperties(prefix = "bean")
   public class MyConfig {
   
       private String message = "a message that can be changed live";
   
       // getter and setters
   
   }

2. To see the changes that are happening, create another bean that prints the message periodically as shown below.

   @Component
   public class MyBean {
   
       @Autowired
       private MyConfig config;
   
       @Scheduled(fixedDelay = 5000)
       public void hello() {
           System.out.println("The message is: " + config.getMessage());
       }
   }

3. You can change the message printed by the application by using a ConfigMap as shown below.

   apiVersion: v1
   kind: ConfigMap
   metadata:
     name: reload-example
   data:
     application.properties: |-
       bean.message=Hello World!

   Any change to the property named bean.message in the Config Map associated with the pod will be reflected in the output of the program.