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Java Dapr-AKS-ACA Workshop

Using Azure Cosmos DB to store the state of a vehicle wtih Dapr

Table of contents

This bonus assignment is about using Azure Cosmos DB as a state store for the TrafficControlService instead of keeping the sate in memory. You will use the Azure Cosmos DB state store component provided by Dapr.

Step 1: Create an Azure Cosmos DB

  1. Open a terminal window.

  2. Azure Cosmos DB account for SQL API is a globally distributed multi-model database service. This account needs to be globally unique. Use the following command to generate a unique name:

    • Linux/Unix shell:

        UNIQUE_IDENTIFIER=$(LC_ALL=C tr -dc a-z0-9 </dev/urandom | head -c 5)
  COSMOS_DB="cosno-dapr-workshop-java-$UNIQUE_IDENTIFIER"
  echo $COSMOS_DB

    • Powershell:

        $ACCEPTED_CHAR = [Char[]]'abcdefghijklmnopqrstuvwxyz0123456789'
  $UNIQUE_IDENTIFIER = (Get-Random -Count 5 -InputObject $ACCEPTED_CHAR) -join ''
  $COSMOS_DB = "cosno-dapr-workshop-java-$UNIQUE_IDENTIFIER"
  $COSMOS_DB

  3. Create a Cosmos DB account for SQL API:

     az cosmosdb create --name $COSMOS_DB --resource-group rg-dapr-workshop-java --locations regionName=eastus failoverPriority=0 isZoneRedundant=False

    The name of the Cosmos DB account must be unique across all Azure Cosmos DB accounts in the world. If you get an error that the name is already taken, try a different name. In the following steps, please update the name of the Cosmos DB account accordingly.

  4. Create a SQL API database:

     az cosmosdb sql database create --account-name $COSMOS_DB --resource-group rg-dapr-workshop-java --name dapr-workshop-java-database

  5. Create a SQL API container:

     az cosmosdb sql container create --account-name $COSMOS_DB --resource-group rg-dapr-workshop-java --database-name dapr-workshop-java-database --name vehicle-state --partition-key-path /partitionKey --throughput 400

    The partition key path is /partitionKey as mentionned in Dapr documentation.

  6. Get the Cosmos DB account URL and note it down. You will need it in the next step and to deploy it to Azure.

     az cosmosdb show --name $COSMOS_DB --resource-group rg-dapr-workshop-java --query documentEndpoint -o tsv

  7. Get the master key and note it down. You will need it in the next step and to deploy it to Azure.

     az cosmosdb keys list --name $COSMOS_DB --resource-group rg-dapr-workshop-java --type keys --query primaryMasterKey -o tsv

Step 2: Configure the Azure Cosmos DB state store component

  1. Open the file dapr/azure-cosmosdb-statestore.yaml in your code editor and look at the content of the file.

  2. Copy or Move this file dapr/azure-cosmosdb-statestore.yaml to dapr/components folder.

  3. Replace the following placeholders in the file dapr/components/azure-cosmosdb-statestore.yaml with the values you noted down in the previous step:

    • <YOUR_COSMOSDB_ACCOUNT_URL> with the Cosmos DB account URL
    • <YOUR_COSMOSDB_MASTER_KEY> with the master key

Step 3: Add the Azure Cosmos DB state store to the TrafficControlService

  1. Open the TrafficControlService project in your code editor and navigate to the DaprVehicleStateRepository class. This class use the Dapr client to store and retrieve the state of a vehicle. Inspect the implementation of this class.

  2. Navigate to the TrafficControlConfiguration class to swith from the InMemoryVehicleStateRepository to the DaprVehicleStateRepository.

  3. Update @Bean method to instantiate DaprVehicleStateRepository instead of InMemoryVehicleStateRepository:

     @Bean
 public VehicleStateRepository vehicleStateRepository(final DaprClient daprClient) {
     return new DaprVehicleStateRepository(daprClient);
 }

  4. Uncomment following @Bean method if not already done:

     //    @Bean
 //    public DaprClient daprClient() {
 //        return new DaprClientBuilder()
 //                .withObjectSerializer(new JsonObjectSerializer())
 //                .build();
 //    }

  5. Check all your code-changes are correct by building the code. Execute the following command in the terminal window:

     mvn package

Now you can test the application

Step 4: Test the application

You’re going to start all the services now.

  1. Make sure no services from previous tests are running (close the command-shell windows).

  2. Open the terminal window and make sure the current folder is VehicleRegistrationService.

  3. Enter the following command to run the VehicleRegistrationService:

    mvn spring-boot:run

  4. Open a new terminal window and change the current folder to FineCollectionService.

  5. Enter the following command to run the FineCollectionService with a Dapr sidecar:

    dapr run --app-id finecollectionservice --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --resources-path ../dapr/components mvn spring-boot:run

  6. Open a new terminal window and change the current folder to TrafficControlService.

  7. Enter the following command to run the TrafficControlService with a Dapr sidecar:

    dapr run --app-id trafficcontrolservice --app-port 6000 --dapr-http-port 3600 --dapr-grpc-port 60000 --resources-path ../dapr/components mvn spring-boot:run

  8. Open a new terminal window and change the current folder to Simulation.

  9. Start the simulation:

    mvn spring-boot:run

You should see the same logs as before. Obviously, the behavior of the application is exactly the same as before.

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