Azure function with Dapr to create event-driven, distributed application¶

In this post we will integrate Azure function app to use Dapr system for pubsub messaging. Azure function could be either triggered by Event Hub or HttpTrigger. For simplicity we will test it with HttpTrigger. Project Repo

System Diagram¶

• Azure function provides easier way to integrate with Event Hub
• Dapr Subsystem hides complexity to deal with PubSub messaging

Getting Ready¶

Getting started with dapr See the dapr Azure Functions quickstart

Requirements

• Dapr installed and configured locally (dapr init)
• Azure Functions Core Tools - v3
• Docker
• .NET Core SDK - enables building of the extension locally in the project
• Node 12 for local debugging of the JavaScript app Or .Net Azure Function

Note: Run Docker on WSL 2 on Windows for better experience

Install Dapr¶

Run in WSL window

wget -q https://raw.githubusercontent.com/dapr/cli/master/install/install.sh -O - | /bin/bash

Run to verify

dapr

Run init

dapr init

Verify Dapr version

dapr --version

Verify containers are running

docker ps

Install dotnet sdk 3.1 and azure-functions-core-tools¶

Install dotnet sdk with azure function tools

Create Azure function App¶

Create a folder for a project or clone empty project from the git¶

Navigate to the folder from WSL console¶

dotnet new sln
func init process --dotnet --docker
dotnet sln azure-function-dapr.sln add ./process/process.csproj
cd process/
func new --name GetMessage --template "HTTP Trigger" --authlevel "anonymous"

ps@Dev-WD MINGW64 /c/Projects/azure-function-dapr/process (main)
$ func extensions install -p Dapr.AzureFunctions.Extension -v 0.12.0-p
review01
dotnet build process.csproj -o bin --no-incremental

To run/debug the function app locally click on "Initialize Project for Use with VS Code"

Update the connection for the WebStorage and run/debug in VS Code

Add Nuget packages¶

• Dapr.AzureFunctions.Extension
• Microsoft.NET.Sdk.Functions
• Microsoft.Azure.WebJobs.Extensions.EventHubs

Create Function GetMessage and add Dapr pubsub¶

```csharp{19,34} using System; using System.IO; using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; using Microsoft.Azure.WebJobs; using Microsoft.Azure.WebJobs.Extensions.Http; using Dapr.AzureFunctions.Extension; using Microsoft.AspNetCore.Http; using Microsoft.Extensions.Logging; using Newtonsoft.Json;

namespace process { public static class GetMessage { [FunctionName("GetMessage")] public static async Task Run( [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req, [DaprPublish(PubSubName = "pubsub", Topic = "alerts")] IAsyncCollector alertEvent, ILogger log) { log.LogInformation("C# HTTP trigger function processed a request.");

        string name = req.Query["name"];

        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        dynamic data = JsonConvert.DeserializeObject(requestBody);
        name = name ?? data?.name;

        string responseMessage = string.IsNullOrEmpty(name)
            ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
            : $"Hello, {name}. This HTTP triggered function executed successfully.";

        await alertEvent.AddAsync(new DaprPubSubEvent(JsonConvert.SerializeObject(new { id = "testobj", message = "This is a test alert" })));

        return new OkObjectResult(responseMessage);
    }
}

} ```

Dapr config file config.yaml¶

yaml apiVersion: dapr.io/v1alpha1 kind: Configuration metadata: name: daprConfig spec: tracing: samplingRate: '1' zipkin: endpointAddress: 'http://localhost:9411/api/v2/spans'

Add messagebus component /components/messagebus.yaml¶

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: pubsub
spec:
  type: pubsub.redis
  metadata:
    - name: redisHost
      value: localhost:6379
    - name: redisPassword
      secretKeyRef:
        key: redis-password
        name: redis

Run Azure Function locally¶

dapr run -a functionapp -p 3001 --components-path ./components/ --config ./config.yaml -- func host start

Trigger Azure function from WSL console¶

curl -X POST -H "Content-Type: application/json" -d '{ "name": "John Gray"}' http://172.21.132.136:7071/api/GetMessage

Validate if the message is in Pubsub¶

docker exec -it dapr_redis /bin/sh
keys *

It should return something like

1) "alerts"

Check actual messages

xread STREAMS alert 0