**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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self._send_sla_callbacks_to_processor(dag)
        if callback:
            self.executor.send_callback(callback)
        else:
            self.log.debug("callback is empty")
    def _send_sla_callbacks_to_processor(self, dag: DAG) -> None:
        """Sends SLA Callbacks to DagFileProcessor if tasks have SLAs set and check_slas=True."""
        if not settings.CHECK_SLAS:
            return
        if not any(isinstance(task.sla, timedelta) for task in dag.tasks):
            self.log.debug("Skipping SLA check for %s because no tasks in DAG have SLAs", dag)
            return
        if not dag.timetable.periodic:
            self.log.debug("Skipping SLA check for %s because DAG is not scheduled", dag)
            return
        dag_model = DagModel.get_dagmodel(dag.dag_id)
        request = SlaCallbackRequest(
            full_filepath=dag.fileloc,
            dag_id=dag.dag_id,
            processor_subdir=dag_model.processor_subdir,
        )
        self.executor.send_callback(request)
    @provide_session
    def _emit_pool_metrics(self, session: Session = NEW_SESSION) -> None: