**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.processor_agent.end()
                except Exception:
                    self.log.exception("Exception when executing DagFileProcessorAgent.end")
            self.log.info("Exited execute loop")
    @provide_session
    def _update_dag_run_state_for_paused_dags(self, session: Session = NEW_SESSION) -> None:
        try:
            paused_runs = (
                session.query(DagRun)
                .join(DagRun.dag_model)
                .join(TaskInstance)
                .filter(
                    DagModel.is_paused == expression.true(),
                    DagRun.state == DagRunState.RUNNING,
                    DagRun.run_type != DagRunType.BACKFILL_JOB,
                )
                .having(DagRun.last_scheduling_decision <= func.max(TaskInstance.updated_at))
                .group_by(DagRun)
            )
            for dag_run in paused_runs:
                dag = self.dagbag.get_dag(dag_run.dag_id, session=session)
                if dag is None:
                    continue
                dag_run.dag = dag
                _, callback_to_run = dag_run.update_state(execute_callbacks=False, session=session)
                if callback_to_run:
                    self._send_dag_callbacks_to_processor(dag, callback_to_run)
        except Exception as e:  
            self.log.exception("Failed to update dag run state for paused dags due to %s", str(e))
    def _run_scheduler_loop(self) -> None: