Defaulting and restrictions for Azure CAPI cluster location field

[marians]

A user creating a CAPZ cluster should be able to decide in which Azure region (location) it gets created.

As with all other configuration options, we want to make setting this value optional. The default value should be (IMO) the same location as the management cluster.

Current implementation

In cluster-azure (as of v0.0.25), the .providerSpecific.location property in the values schema has the static default value westeurope. See schema.

As a result, the field appears in the web UI cluster creation form, pre-filled with westeurope.

If the management cluster is in a different region, e. g. germanywestcentral, and the user wants to use the same region for management and workload cluster (which is sensible based on latency and cross-region traffic cost), the user must know the right location value to set.

If the user wants to create the cluster in a different region, they must know the correct region name to use for the field value.

Currently we only support a selected subset of all Azure regions, defined in capi-image-builder.

Solutions

Here are some ideas:

• Add the valid region names to the .providerSpecific.location schema as enum values, so that only valid options are selectable.
• Keep the field empty by default (do not set any default string). Then on cluster app deployment, apply the management cluster's region as a default value, in case no value is given.

[marians]

With giantswarm/cluster-azure#144 we have set the location field to only allow for input/selection of predefined cloud provider regions. So honeybadger's job here is done for now.

For the backend-side defaulting I leave this open.