**Description**


It would be great if the metrics we publish in Airflow change to include TAGs for "variable" parts of those (such as dag_id, task_id, pool name) rather than being part of the metrics.

See here: https://airflow.apache.org/docs/1.10.12/metrics.html, https://airflow.readthedocs.io/en/latest/logging-monitoring/metrics.html  - those variable parts should be tags.

We might consider to change those metrics by default in 2.0 and possibly introduce a backport in 1.10.13 to allow people to migrate.


**Use case / motivation**

Having the variable parts of the metrics makes it really difficult to aggregate the metrics. Seems that statsd python library does not support tags, but there are possible solutions by installing extensions:

https://stackoverflow.com/questions/49852654/sending-statsd-metrics-with-tags-from-python-client

**Related Issues**

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"""Returns the pipe for sending Callbacks to DagProcessorManager."""
        if not self._parent_signal_conn:
            raise ValueError("Process not started.")
        return self._parent_signal_conn
    def wait_until_finished(self) -> None:
        """Waits until DAG parsing is finished."""
        if not self._parent_signal_conn:
            raise ValueError("Process not started.")
        if self._async_mode:
            raise RuntimeError("wait_until_finished should only be called in sync_mode")
        while self._parent_signal_conn.poll(timeout=None):
            try:
                result = self._parent_signal_conn.recv()
            except EOFError:
                return
            self._process_message(result)
            if isinstance(result, DagParsingStat):
                
                
                return
    @staticmethod
    def _run_processor_manager(