We have a Multi-tenant web site and service that requires each of our customers to gain access to their on premise ERP data. The Azure Service Bus seems to be a great choice when the requirement is to NOT require IT to open ports through the firewall. I am struggling to determine the best approach between relay and messaging. Specifically here are my concerns
1. Scalable isolation - meaning thousands of customers with each logging into our site would map back to their specific endpoint to establish a conversation to a service in their environment.
2. Cost effective
Since we really only need to establish a connection back into the customer environment when they are online in our site, I don't want the billing to reflect "idle" time. Ideally the connection would activate when they log into our site. Or, maybe my billing concern is misplaced. Any guidance would be appreciated!!