**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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"""Make sure we only set SchedulerJobs to failed, not all jobs"""
        session = settings.Session()
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        self.scheduler_job.state = State.RUNNING
        self.scheduler_job.latest_heartbeat = timezone.utcnow()
        session.add(self.scheduler_job)
        session.flush()
        old_job = SchedulerJob(subdir=os.devnull)
        old_job.state = State.RUNNING
        old_job.latest_heartbeat = timezone.utcnow() - timedelta(minutes=15)
        session.add(old_job)
        session.flush()
        old_task_job = BaseJob()  
        old_task_job.state = State.RUNNING
        old_task_job.latest_heartbeat = timezone.utcnow() - timedelta(minutes=15)
        session.add(old_task_job)
        session.flush()
        with caplog.at_level("INFO", logger="airflow.jobs.scheduler_job"):
            self.scheduler_job.adopt_or_reset_orphaned_tasks(session=session)
        session.expire_all()
        assert old_job.state == State.FAILED
        assert old_task_job.state == State.RUNNING
        assert "Marked 1 SchedulerJob instances as failed" in caplog.messages
    def test_send_sla_callbacks_to_processor_sla_disabled(self, dag_maker):