Dapr pub/sub using Solace Cloud

In this demo, you'll run publisher and subscriber microservices locally, and send/receive messages using Solace Cloud, to demonstrate how Dapr enables a publish-subscribe pattern.

The publisher service (checkout) will generate messages and send these to a specific topic (topic:marc/orders), while the subscriber service (order-processor) will listen for messages at the same topic. See the Dapr pub/sub overview to understand when this pattern might be a good choice for your software architecture.

With Dapr, the application code is using set of common building block APIs. The pub/sub API is such a building block. Dapr allows to switch between different pub/sub implementations by using component files. These are yaml files that contain resource specific information. This means the application code is not coupled to the implementation of the pub/sub resource. In this demo the Solace AMQP component is used.

Prerequisites

.NET 6 SDK
Dapr CLI
Solace Cloud account. If you don't have one, you can sign up for a free trial.

1. Setup Solace Cloud

In the Solace Cloud portal, go to Cluster Manager and create a new service.
Provide a service name, service type, and choose a cloud where the service will be deployed.
Click Create Service and wait until the service is deployed.
Once the service is deployed, navigate to the Connect tab of the service and expand the AMQP section. Note the information underneath the Connection Details. This will be needed in the Dapr pubsub component file in the next step.

2. Update the Dapr pubsub component file

Clone this repository locally and open it in your IDE.
Rename the resources/pubsub.yaml.template file to resources/pubsub.yaml. This is the Dapr pub/sub component file that will contain the details to connect to Solace Cloud.

The pubsub.yaml file has been added to .gitignore to prevent accidental check-in of credentials for this demo. For production use, the yaml files should be checked into source control and secret store references should be used, instead of plain text values.

Copy the username, password, and the secured AMQP host values from the Solace AMQP Connection Details to the pubsub.yaml file.

The result should look like this:

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
name: pubsub-component
spec:
type: pubsub.solace.amqp
version: v1
metadata:
- name: url
    value: "amqps://<SOLACE_SECURED_AMQP_HOST>"
- name: username
    value: "solace-cloud-client"
- name: password
    value: "<SOLACE_PASSWORD>"

3. Run the .NET message subscriber with Dapr

Open a terminal, navigate to the order-processor directory and build the project:
```
cd ./order-processor
dotnet build
```

Run the .NET subscriber app with Dapr:

dapr run --app-id order-processor --resources-path ../resources/ --app-port 7002 -- dotnet run

4. Run the .NET message publisher with Dapr

Open another terminal, navigate to the checkout directory and build the project:
```
cd ./checkout
dotnet restore
dotnet build
```

Run the .NET publisher app with Dapr:

dapr run --app-id checkout-sdk --resources-path ../resources/ -- dotnet run

The following output should be visible in the terminals:

Publisher output:

== APP == Published data: Order { OrderId = 1 }
== APP == Published data: Order { OrderId = 2 }
== APP == Published data: Order { OrderId = 3 }
== APP == Published data: Order { OrderId = 4 }
== APP == Published data: Order { OrderId = 5 }
== APP == Published data: Order { OrderId = 6 }
== APP == Published data: Order { OrderId = 7 }
== APP == Published data: Order { OrderId = 8 }
== APP == Published data: Order { OrderId = 9 }
== APP == Published data: Order { OrderId = 10 }

Subscriber output: