Loki Promtail dynamic label values extraction from logs - scrap-config

Question

The Log entry looks like this

2022-05-12 10:32:19,659 - root:loadrequestheaders:33 - INFO: otds=XYZ, domain=XYZ, username=user, origin=10.98.76.67

I tried to add the promtail configuration to scrap log entry to get new labels : Updated ConfigMap - loki-promtail with below content

 - job_name: kubernetes-pods-static
      pipeline_stages:
      - match:
          selector: '{container="model"}'
          stages:
          - regex:
              expression: '\.*username=(?P<username>\S+).*origin=(?P<origin>\S+)'
          - labels:
              username:
              origin:

I could see loki pods are running successfully with above config map update but I don't see the entries "username and origin" - in the labels list Any suggestion on how to add new labels in loki datasource.

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