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How-To: Manage configuration from a store

Learn how to get application configuration and subscribe for changes

Introduction

This HowTo uses the Redis configuration store component as an example on how to retrieve a configuration item.

This API is currently in Alpha state and only available on gRPC. An HTTP1.1 supported version with this URL syntax /v1.0/configuration will be available before the API is certified into Stable state.

Example:

The below code examples loosely describe an application that processes orders. In the examples, there is an order processing service which has a Dapr sidecar. The order processing service uses Dapr to retrieve the configuration from a Redis configuration store.

Diagram showing get configuration of example service

Step 1: Create a configuration item in store

First, create a configuration item in a supported configuration store. This can be a simple key-value item, with any key of your choice. For this example, we’ll use the Redis configuration store component.

Run Redis with Docker

docker run --name my-redis -p 6379:6379 -d redis

Save an item

Using the Redis CLI, connect to the Redis instance:

redis-cli -p 6379 

Save a configuration item:

MSET orderId1 "101||1" orderId2 "102||1"

Configure a Dapr configuration store

Save the following component file, for example to the default components folder on your machine. You can use this as the Dapr component YAML for Kubernetes using kubectl or when running with the Dapr CLI. Note: The Redis configuration component has identical metadata to the Redis state store component, so you can simply copy and change the Redis state store component type if you already have a Redis state store YAML file.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: configstore
spec:
  type: configuration.redis
  metadata:
  - name: redisHost
    value: localhost:6379
  - name: redisPassword
    value: <PASSWORD>

Get configuration items using Dapr SDKs


//dependencies
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Dapr.Client;

//code
namespace ConfigurationApi
{
    public class Program
    {
        private static readonly string CONFIG_STORE_NAME = "configstore";

        [Obsolete]
        public static async Task Main(string[] args)
        {
            using var client = new DaprClientBuilder().Build();
            var configuration = await client.GetConfiguration(CONFIG_STORE_NAME, new List<string>() { "orderId1", "orderId2" });
            Console.WriteLine($"Got key=\n{configuration[0].Key} -> {configuration[0].Value}\n{configuration[1].Key} -> {configuration[1].Value}");
        }
    }
}

Navigate to the directory containing the above code and run the following command to launch the application along with a Dapr sidecar:

dapr run --app-id orderprocessing --components-path ./components -- dotnet run

//dependencies
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.DaprPreviewClient;
import io.dapr.client.domain.ConfigurationItem;
import io.dapr.client.domain.GetConfigurationRequest;
import io.dapr.client.domain.SubscribeConfigurationRequest;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

//code
private static final String CONFIG_STORE_NAME = "configstore";

public static void main(String[] args) throws Exception {
    try (DaprPreviewClient client = (new DaprClientBuilder()).buildPreviewClient()) {
      List<String> keys = new ArrayList<>();
      keys.add("orderId1");
      keys.add("orderId2");
      GetConfigurationRequest req = new GetConfigurationRequest(CONFIG_STORE_NAME, keys);
      try {
        Mono<List<ConfigurationItem>> items = client.getConfiguration(req);
        items.block().forEach(ConfigurationClient::print);
      } catch (Exception ex) {
        System.out.println(ex.getMessage());
      }
    }
}

Navigate to the directory containing the above code and run the following command to launch the application along with a Dapr sidecar:

dapr run --app-id orderprocessing --components-path ./components mvn spring-boot:run

#dependencies
from dapr.clients import DaprClient
#code
with DaprClient() as d:
        CONFIG_STORE_NAME = 'configstore'
        keys = ['orderId1', 'orderId2']
        #Startup time for dapr
        d.wait(20)
        configuration = d.get_configuration(store_name=CONFIG_STORE_NAME, keys=[keys], config_metadata={})
        print(f"Got key={configuration.items[0].key} value={configuration.items[0].value} version={configuration.items[0].version}")

Navigate to the directory containing the above code and run the following command to launch the application along with a Dapr sidecar:

dapr run --app-id orderprocessing --components-path ./components python3 OrderProcessingService.py

Get configuration items using gRPC API

Using your favorite language, create a Dapr gRPC client from the Dapr proto. The following examples show Java, C#, Python and Javascript clients.



Dapr.ServiceBlockingStub stub = Dapr.newBlockingStub(channel);
stub.GetConfigurationAlpha1(new GetConfigurationRequest{ StoreName = "redisconfigstore", Keys = new String[]{"myconfig"} });


var call = client.GetConfigurationAlpha1(new GetConfigurationRequest { StoreName = "redisconfigstore", Keys = new String[]{"myconfig"} });

response = stub.GetConfigurationAlpha1(request={ StoreName: 'redisconfigstore', Keys = ['myconfig'] })

client.GetConfigurationAlpha1({ StoreName: 'redisconfigstore', Keys = ['myconfig'] })
Watch configuration items

Create a Dapr gRPC client from the Dapr proto using your preferred language. Then use the proto method SubscribeConfigurationAlpha1 on your client stub to start subscribing to events. The method accepts the following request object:

message SubscribeConfigurationRequest {
  // The name of configuration store.
  string store_name = 1;

  // Optional. The key of the configuration item to fetch.
  // If set, only query for the specified configuration items.
  // Empty list means fetch all.
  repeated string keys = 2;

  // The metadata which will be sent to configuration store components.
  map<string,string> metadata = 3;
}

Using this method, you can subscribe to changes in specific keys for a given configuration store. gRPC streaming varies widely based on language - see the gRPC examples here for usage.

Stop watching configuration items

After you have subscribed to watch configuration items, the gRPC-server stream starts. This stream thread does not close itself, and you have to do by explicitly call the UnSubscribeConfigurationRequest API. This method accepts the following request object:

// UnSubscribeConfigurationRequest is the message to stop watching the key-value configuration.
message UnSubscribeConfigurationRequest {
  // The name of configuration store.
  string store_name = 1;
  // Optional. The keys of the configuration item to stop watching.
  // Store_name and keys should match previous SubscribeConfigurationRequest's keys and store_name.
  // Once invoked, the subscription that is watching update for the key-value event is stopped
  repeated string keys = 2;
}

Using this unsubscribe method, you can stop watching configuration update events. Dapr locates the subscription stream based on the store_name and any optional keys supplied and closes it.

Next steps


Last modified July 26, 2022: Update translations for v1.6 (#2665) (e18b8c6)