**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**

<!-- Is there currently another issue associated with this? -->

call_args = self.scheduler_job._send_dag_callbacks_to_processor.call_args[0]
        assert call_args[0].dag_id == dr.dag_id
        assert call_args[1] is not None
        assert call_args[1].msg == msg
        session.rollback()
        session.close()
    def test_dagrun_notify_called_success(self, dag_maker):
        with dag_maker(
            dag_id="test_dagrun_notify_called",
            on_success_callback=lambda x: print("success"),
            on_failure_callback=lambda x: print("failed"),
            processor_subdir=TEST_DAG_FOLDER,
        ):
            EmptyOperator(task_id="dummy")
        dag_listener.clear()
        get_listener_manager().add_listener(dag_listener)
        executor = MockExecutor(do_update=False)
        self.scheduler_job = SchedulerJob(executor=executor)
        self.scheduler_job.dagbag = dag_maker.dagbag
        self.scheduler_job.processor_agent = mock.MagicMock()
        session = settings.Session()
        dr = dag_maker.create_dagrun()
        ti = dr.get_task_instance("dummy")
        ti.set_state(State.SUCCESS, session)
        with mock.patch.object(settings, "USE_JOB_SCHEDULE", False):
            self.scheduler_job._do_scheduling(session)
        assert dag_listener.success[0].dag_id == dr.dag_id
        assert dag_listener.success[0].run_id == dr.run_id
        assert dag_listener.success[0].state == DagRunState.SUCCESS
    def test_do_not_schedule_removed_task(self, dag_maker):