**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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dr = dag.create_dagrun(
                run_type=DagRunType.SCHEDULED,
                execution_date=dr.data_interval_end,
                state=None,
                session=session,
            )
        ex_date = dr.execution_date
        for tid, state in expected_task_states.items():
            if state != State.FAILED:
                continue
            self.null_exec.mock_task_fail(dag_id, tid, dr.run_id)
        try:
            dag = DagBag().get_dag(dag.dag_id)
            
            assert not isinstance(dag, SerializedDAG)
            
            
            dag.run(start_date=ex_date, end_date=ex_date, executor=self.null_exec, **run_kwargs)
        except AirflowException:
            pass
        
        dr = DagRun.find(dag_id=dag_id, execution_date=ex_date, session=session)
        dr = dr[0]
        dr.dag = dag
        assert dr.state == dagrun_state
        
        for task_id, expected_state in expected_task_states.items():
            ti = dr.get_task_instance(task_id)
            assert ti.state == expected_state
    def test_dagrun_fail(self):