**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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external_trigger=False,
                    session=session,
                    dag_hash=dag_hash,
                    creating_job_id=self.id,
                )
                Stats.incr("dataset.triggered_dagruns")
                dag_run.consumed_dataset_events.extend(dataset_events)
                session.query(DatasetDagRunQueue).filter(
                    DatasetDagRunQueue.target_dag_id == dag_run.dag_id
                ).delete()
    def _should_update_dag_next_dagruns(self, dag, dag_model: DagModel, total_active_runs: int) -> bool:
        """Check if the dag's next_dagruns_create_after should be updated."""
        if total_active_runs >= dag.max_active_runs:
            self.log.info(
                "DAG %s is at (or above) max_active_runs (%d of %d), not creating any more runs",
                dag_model.dag_id,
                total_active_runs,
                dag.max_active_runs,
            )
            dag_model.next_dagrun_create_after = None
            return False
        return True
    def _start_queued_dagruns(self, session: Session) -> None:
        """Find DagRuns in queued state and decide moving them to running state."""
        dag_runs = self._get_next_dagruns_to_examine(DagRunState.QUEUED, session)
        active_runs_of_dags = defaultdict(
            int,
            DagRun.active_runs_of_dags((dr.dag_id for dr in dag_runs), only_running=True, session=session),
        )
        def _update_state(dag: DAG, dag_run: DagRun):