This is a bit of a quasi-rant/asking for help with an issue:

I am trying to create a Read Replica for a MySQL server using an ARM template. I am running into an issue when applying the same template again and getting a "SeverNameAlreadyExists" error. To reproduce the error I have this:

1. Template A creates a MySQL server and a sub-resource of a read replica dependent on that server
   Results: This works the first time, every time.
2. Run Template A again with no changes.
   Results: Replica Creation fails on "ServerNameAlreadyExists"
3. Template B creates just a MySQL server
   Results: A MySQL server is created
4. Run Template B again.
   Results: No changes to the MySQL server from the original run in (3). This can be repeated as much as I want.
5. Template C creates just a MySQL server read replica using an already existing server as its parent
   Results: Read Replica for the parent server is created normally
6. Run Template C again.
   Results: I receive the error "ServerNameAlreadyExists"
7. Modify Template C so that createMode is Default instead of of Replica
   Results: Applies successfully. No apparent changes to the Read Replica / Parent relationship. This can be run multiple times.

Per MS Support this is expected behavior.

While I am new to ARM, I have used other applications that are idempotent* (Terraform, Ansible) and this to me seems to violate the following statement in Azure's documentation (emphasis mine):

• Repeatable results: Repeatedly deploy your infrastructure throughout the development lifecycle and have confidence your resources are deployed in a consistent manner. Templates are idempotent, which means you can deploy the same template many times and get the same resource types in the same state. You can develop one template that represents the desired state, rather than developing lots of separate templates to represent updates.

Right now, in order to avoid this error, we have to consider the state of the deployment and make changes to the parameters at in step (7). This feels fairly cludgey to me.

Has anyone else experienced this before? Is there a better work around?

* I know TF and Ansible have some quirks sometimes that don't make them completely idempotent.