TAP Sensors Demo App

An application to demonstrate the capabilities of VMware Tanzu Application Platform.

This application consists of two services:

• Sensor service(s), which periodically publishes events with sensor data
• Hub service, which consumes sensors' events and stores data in its database; also comes with a web dashboard

Features:

• Spring Cloud Stream, a framework built on top of Spring Boot and Spring Integration, is used as a flexible messaging abstraction. Spring Cloud Stream supports a variety of binder implementations. In this case, we are using the one for RabbitMQ.
• Service Bindings - binding an application workload to a backing service such as a RabbitMQ is one of the most important use cases within the context of the VMware Tanzu Application Platform. This use case is made possible by the Service Binding Specification for Kubernetes. With the service binding that is defined in the workload.yml (found under config folder in the respective app), the credentials that are required for the connection to the RabbitMQ cluster or PostgreSQL are magically injected into the container and the Spring Boot application.
• VMware Aria Operations for Applications (a.k.a. Tanzu Observability, a.k.a. Wavefront) - monitoring a running application is one of the most important Day-2 operations concern. A Spring Boot provides seamless integrates with Wavefront and publishes application metrics and allows for tracing requests across a distributed system including services such as RabbitMQ and PostgreSQL.

Prerequisites

• Access to an instance of VMware Tanzu Application Platform (dev, light or full)
• A namespace
• Postgres Operator package installed on TAP
• Rabbit Cluster Operator package installed on TAP
• Privileges of:
  • platform operator, to create ClusterInstanceClass and ClusterRole k8s resources
  • app operator, to create RabbitmqCluster, Postgres and ResourceClaim k8s resources

Service Operator - Make services available

To run this application with VMware Tanzu Application Platform, you need a RabbitMQ cluster running in the same Kubernetes namespace (e.g. provisioned via the RabbitMQ Cluster Operator for Kubernetes).

You also need an instance of PostgreSQL database running in the same Kubernetes namespace (e.g. provisioned via the VMware Postgres Operator).

RabbitMQ Cluster

To make services available for an app operator to claim, the service operator needs to run the following commands:

kubectl apply -f config/service-operator/rabbit-claims-rbac.yml
kubectl apply -f config/service-operator/rabbit-cluster-instance-class.yml
kubectl apply -f config/service-operator/sensors-rabbit.yml

PostgreSQL

To make services available for an app operator to claim, the service operator needs to run the following commands:

kubectl apply -f config/service-operator/postgres-cluster-instance-class.yml
kubectl apply -f config/service-operator/postgres-claims-rbac.yml
kubectl apply -f config/service-operator/sensors-db.yml

App Operator

RabbitMQ Cluster

To claim RabbitMQ service:

kubectl apply -f config/app-operator/sensors-rabbit-claim.yml

PostgreSQL

To claim Postgres database:

kubectl apply -f config/app-operator/sensors-db-claim.yml

Deploying application/services

Sensor service

To deploy the sensor service on VMware Tanzu Application Platform, execute the following command:

tanzu apps workload apply -f sensor/config/workload.yml

Hub service

To deploy the hub service on VMware Tanzu Application Platform, execute the following command:

tanzu apps workload apply -f hub/config/workload.yml

You can access the application's UI using the URL shown by running the following command (provided you have DNS configured for Cloud Native Runtimes):

tanzu app workload get tap-sensors-hub

Configuring application/services

Wavefront

For both services, to be able to publish metrics to Wavefront, they need to be configured with the Wavefront URI and API token. Each service comes with an application.yml configuration file under src/main/resources. They have been preconfigured for the Wavefront SaaS freemium account, however the API token was omitted in the configuration.

If you want to publish metrics to other instance of Wavefront/Tanzu Observability, you can change application.yml configs accordingly.

If you want to use the freemium one, please follow the steps below to generate and set the API token.

Generate Wavefront freemium token

1. Clean old token - optional If you have ever configured Wavefront freemium token, it leaves behind some file with a token on your file system. Please run the provided script for cleaning that up:

bin/clean-wavefront-token

2. Start the sensor service Start one of the services on your local, lets say the sensor one From the root folder of the project, run the following commands:

docker compose up -d
./gradlew ./gradlew sensor:bootRun

See more on running the application locally below

3. Extract API token from logs When the service starts successfully it will connect to the Wavefront SaaS and provision you a freemium account and crate an API token. The details are logged in the console and include the Wavefront URI, API token and a unique link to your dashboard within Wavefront. Please capture those details.

4. Add API token to app configuration You can simply set the environment variable:

export MANAGEMENT_WAVEFRONT_API_TOKEN=<your-api-token>

Alternatively, you can add api-token under the management.wavefront section, at the same level as uri.

Running on local

Prerequisites

• Java Development Kit (JDK) 17 or newer
• Docker Desktop / Rancher Desktop for running RabbitMQ and PostgreSQL services

Note: all listed commands assume that you are running them from the root folder of the project

Starting RabbitMQ and PostgreSQL services

Pre-req: Make sure your Docker/Rancher Desktop is running.

For your convenience, this project comes with docker-compose.yml file that allows you to start all the required services. To make it even easier, you can find scripts in the bin folder:

To start both services, run

bin/services-up

To shut both services down, run:

bin/services-down

Start both hub and sensor services

Pre-req: Make sure RabbitMQ and PostgreSQL services are running as docker containers (docker compose ps)

For your convenience, we provided a script that allows you to start both services:

bin/run

You can also run individual services with these commands

./gradlew hub:bootRun
./gradlew sensor:bootRun

Valid the application is working

Sensor service

After the sensor service starts successfully it generates a sensor event every second. Each time a sensor event is emitted it logs detail of that event. Check the console for logs.

Also, the service has healthcheck endpoint: http://localhost:8081/actuator/health

Hub service

Every time the hub service receives a sensor event, it logs details of that event. Assuming your sensor service is running and emitting events, your hub service should receive them and log them. Check the console for logs.

Also, the service has healthcheck endpoint: http://localhost:8080/actuator/health

Finally, you can open Hub's dashboard in your browser, and you should see a table containing realtime sensor data (refreshes every few seconds).