**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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def setup_method(self):
        self.statsd_client = Mock(spec=statsd.StatsClient)
        self.stats = SafeStatsdLogger(self.statsd_client)
    def test_increment_counter_with_valid_name(self):
        self.stats.incr("test_stats_run")
        self.statsd_client.incr.assert_called_once_with("test_stats_run", 1, 1)
    def test_stat_name_must_be_a_string(self):
        self.stats.incr([])
        self.statsd_client.assert_not_called()
    def test_stat_name_must_not_exceed_max_length(self):
        self.stats.incr("X" * 300)
        self.statsd_client.assert_not_called()
    def test_stat_name_must_only_include_allowed_characters(self):
        self.stats.incr("test/$tats")
        self.statsd_client.assert_not_called()
    def test_timer(self):
        with self.stats.timer("empty_timer"):
            pass
        self.statsd_client.timer.assert_called_once_with("empty_timer")
    def test_empty_timer(self):
        with self.stats.timer():
            pass
        self.statsd_client.timer.assert_not_called()
    def test_timing(self):