Azure Service Bus¶

Service Bus event-source allows you to consume messages from queus and topics in Azure Service Bus and helps sensor trigger workflows.

Event Structure¶

The structure of an event dispatched by the event-source over the eventbus looks like following,

    {
        "context": {
          "id": "unique_event_id",
          "source": "name_of_the_event_source",
          "specversion": "cloud_events_version",
          "type": "type_of_event_source",
          "datacontenttype": "type_of_data",
          "subject": "name_of_the_configuration_within_event_source"
          "time": "event_time",
        },
        "data": {
            "applicationProperties": "ApplicationProperties can be used to store custom metadata for a message",
            "body": "Body represents the message body",
            "contentType": "ContentType is the MIME content type",
            "correlationID": "CorrelationID is the correlation identifier",
            "enqueuedTime": "EnqueuedTime is the time when the message was enqueued",
            "messageID": "ID of the message",
            "replyTo": "ReplyTo is an application-defined value specify a reply path to the receiver of the message",
            "sequenceNumber": "SequenceNumber is a unique number assigned to a message by Service Bus",
            "subject": "Subject enables an application to indicate the purpose of the message, similar to an email subject line",
        }
    }

Setup¶

Create a queue called test either using Azure CLI or Azure Service Bus management console.
Fetch your connection string for Azure Service Bus and base64 encode it.

Create a secret called azure-secret as follows.

apiVersion: v1
kind: Secret
metadata:
  name: azure-secret
type: Opaque
data:
  connectionstring: <base64-connection-string>

Deploy the secret.

kubectl -n argo-events apply -f azure-secret.yaml

Create the event source by running the following command.

kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/event-sources/azure-service-bus.yaml

Inspect the event-source pod logs to make sure it was able to listen to the queue specified in the event source to consume messages.

Create a sensor by running the following command.

kubectl apply -n argo-events -f https://raw.githubusercontent.com/argoproj/argo-events/stable/examples/sensors/azure-service-bus.yaml

Lets set up a Service Bus client. If you don't have azure-servicebusinstalled, run.
```
python -m pip install azure-servicebus --upgrade
```

Open a python REPL and run the following code to send a message on the queue called test.

Before running the code, make sure you have the SERVICE_BUS_CONNECTION_STRING environment variable set. This is the connection string for your Azure Service Bus.

import os, json
from azure.servicebus import ServiceBusClient, ServiceBusMessage
servicebus_client = ServiceBusClient.from_connection_string(conn_str=os.environ['SERVICE_BUS_CONNECTION_STRING'])
with servicebus_client:
    sender = servicebus_client.get_queue_sender(queue_name="test")
    with sender:
        message = ServiceBusMessage('{"hello": "world"}')
        sender.send_messages(message)

As soon as you publish a message, sensor will trigger an Argo workflow. Run argo list to find the workflow.