Overwrite source_workload metric using istio operator

I would like to overwrite the source_workload tag in the request_bytes_bucket metric due to high cardinality issues generated by a specific workload - I do not want to drop the source_workload tag as that will break Kiali functionality and affect other workloads that do not have this issue - I've tried using the following definition but this does not seem to be working, there doesnt appear to be many examples so I'm not sure if a ternary or regex can be used in this scenario:

apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
metadata:
  name: istio
spec:
  values:
    telemetry:
      v2:
        prometheus:
          configOverride:
            inboundSidecar:
              metrics:
                - name: request_bytes_bucket
                  dimensions:
                    source_workload: "matches(istio_request_bytes_bucket.source_workload, \"source-workload-prefix-.*\") ? istio_request_bytes_bucket.source_app : istio_request_bytes_bucket.source_workload"

Solution

To get this working I had to drop the 'istio' prefix, the 'bucket' suffix and add an additional set of single quotes around the value e.g.

values:
   telemetry:
     enabled: true
     v2:
       enabled: true
       prometheus:
         configOverride:
           inboundSidecar:
             stat_prefix: istio
             metrics:
               - name: request_bytes
                 dimensions:
                  source_workload: "'test'"