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

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

• Please see the Guide

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

Use Visual Studio Code and RestClient extension to publish the message

• RestClient extension must be installed within Visual Studio Code
• Open vscode-rest-test\create-product.http by Visual Studio Code; then click on Send Request and observe the log

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