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An example of Dapr Pub-Sub and Web Api .NET Core without using Dapr Dotnet-SDK

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Dapr Pub-Sub with .NET Core Sample (without using Dapr Dotnet-SDK)

publisher-api-ci first-subscriber-api-ci second-subscriber-api-ci

This sample includes 3 .NET Core WebApi as below:

  • 1 publisher
    • Example.Dapr.Publisher
  • 2 subcribers:
    • Example.Dapr.FirstSubscriber will subscribe on ProductCreated topic
    • Example.Dapr.SecondSubscriber will subscribe on ProductCreated topic

Prerequisites

  1. Install Docker for Desktop
  2. Install Dapr Cli

How to deploy to Kubernetes

Run projects with Dapr Cli

  1. Starting Publisher

    cd .\source\Example.Dapr.Publisher\
    dapr run --app-id example-publisher --app-port 5000 dotnet run
  2. Starting FirstSubscriber

    cd .\source\Example.Dapr.FirstSubscriber\
    dapr run --app-id example-first-subscriber --app-port 5001 dotnet run
  3. Starting SecondSubscriber

    cd .\source\Example.Dapr.SecondSubscriber\
    dapr run --app-id example-second-subscriber --app-port 5002 dotnet run

Use the CLI to Publish Messages to Subscribers

dapr publish --topic ProductCreated --payload "{ \"ProductId\": 1, \"Code\":\"this-is-a-test\" }"

Both subscribers which are example-first-subscriber & example-second-subscriber receive a message

Logs of FirstSubscriber

Logs of SecondSubscriber

Use Visual Studio Code and RestClient extension to publish the message

Use RestClient Extension of Visual Studio Code

Notes

For Subscribers

  • Since we subscribe on ProductCreated topic, hence we have to define the endpoint as below
[HttpPost("ProductCreated")]
public IActionResult SubscribeProductCreated(CloudEvent request)
  • Remember add CloudEventJsonInputFormatter
services
    .AddControllers(opts =>
    {
        opts.InputFormatters.Insert(0, new CloudEventJsonInputFormatter());
    })
    .AddJsonOptions(opts => opts.JsonSerializerOptions.PropertyNameCaseInsensitive = true);
  • Then expose to Dapr runtime by define the MapGet inside Startup.cs
app.UseEndpoints(endpoints =>
{
    endpoints.MapControllers();
    endpoints.MapGet("/dapr/subscribe", async context =>
    {
        var channels = new[] { "ProductCreated" };
        var toJson = JsonSerializer.Serialize(channels);
        context.Response.ContentType = "application/json";
        await context.Response.WriteAsync(toJson);
    });
});

For Publisher

  • First, we define the DaprPublisher as Http Client in Startup.cs
services
    .AddHttpClient<DaprPublisher>((provider, client) =>
    {
        var logger = provider.GetRequiredService<ILogger<Startup>>();

        var daprPort = Environment.GetEnvironmentVariable("DAPR_HTTP_PORT") ?? "3500";

        var baseAddress = $"http://localhost:{daprPort}";

        logger.LogInformation($"[{nameof(Startup)}] - Publish Address: {baseAddress}");

        client.BaseAddress = new Uri(baseAddress, UriKind.Absolute);
    });
  • Then, in order to publish the message to ProductCreated topic, we just simply make a POST request to http://localhost:{DAPR_HTTP_PORT}/v1.0/publish/ProductCreated. See the code at DaprPublisher.cs

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Resources

  1. Concepts of Publish/Subscribe Messaging
  2. Configure Redis
  3. Publish Topic
  4. Consume Topic
  5. Examples
  6. CloudEvent sdk-csharp

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An example of Dapr Pub-Sub and Web Api .NET Core without using Dapr Dotnet-SDK

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