I have tried to find out how I can notify multiple microservice (MS) instances via eventdriven approach if their Azure App Configuration values are changed. I have found that I via Eventgrid can listen on changes in Azure App Configuration but I don't find any built in method to distribute event to multiple instances (many MS instances)... I can choose webhook but then it will be to one instance, I can choose other eventdriven approaches as Event Hub but then I have to setup that and I wonder what is best practice for this? I don't want each MS to poll for changes rather to be notified and receive what has been changed or is there a better built in approach/strategy?
For push-based configuration updates from Azure App Configuration, the suggested approach is to forward events to a Service Bus Topic. Azure Service Bus SDK provides RegisterMessageHandler method that allows clients to register a message handler that would be triggered for every message recieved in the topic. Each instance of the microservice could set up a subscription to this Service Bus Topic and register a message handler during service initialization to receive configuration updates.
The instructions to set up a service bus topic can be found here. Details on the protocols available to subscribe to service bus topics and the required firewall configuration can be found here. Since a single topic can support up to 2000 subscriptions, this approach would allow up to 2000 service instances.