Spark config for master.aliveWorkers


i am trying to get a metric called master.aliveWorkers from my Master Spark node. Spark is in version 2.4.4
My config looks like this:

  # These come from the master
  # Example: master.aliveWorkers
  - pattern: "metrics<name=master\\.(.*)><>Value"
    name: spark_master_$1

when i access metrics on port 9090 there is no such metrics, some other there are.
Is my config wrong or is it something else?