What is *.servicebus.windows.net used for in Azure Data Factory?

Question

In a hybrid scenario with self-hosted integration runtime installed to connect to on-premises database, and firewall allowing outbound port 443 *.frontend.clouddatahub.net which according to docs is Required by the self-hosted integration runtime to connect to the Data Factory service.

The integration runtime is able to connect to Azure Data Factory with status Running (Limited) and a warning saying that the cloud service cannot connect to the integration runtime through Service Bus.

The same docs say that outbound port 443 *.servicebus.windows.net is Required by the self-hosted integration runtime to connect to data movement services in Azure Data Factory. If I understand correctly this includes copying data to the on-premises database and therefore is required.

What exactly is Service Bus used for in Azure Data Factory, and preferably from the integration runtime perspective? The figure for Hybrid scenarios shows Command Channel and Data Channel. Does the latter represent data sent over Service Bus?

Any insight will be appreciated. Thanks for your consideration and have a nice day!

Answer 1

It's not data, but instructions. If you look at the webpage on creating self-hosted integration run times it states this:

Azure Data Factory communicates with the self-hosted integration runtime to schedule and manage jobs. Communication is via a control channel that uses a shared Azure Service Bus Relay connection

Basically Factory is saying to integration runtime "Do you want me to do anything?". You do not have to provision or configure Service Bus so I wouldn't worry about it too much.