**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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"""Stops all running processors."""
        for processor in self._processors.values():
            Stats.decr(
                "dag_processing.processes", tags={"file_path": processor.file_path, "action": "terminate"}
            )
            processor.terminate()
    def end(self):
        """Kill all child processes on exit since we don't want to leave them as orphaned."""
        pids_to_kill = self.get_all_pids()
        if pids_to_kill:
            kill_child_processes_by_pids(pids_to_kill)
    def emit_metrics(self):
        """
        Emit metrics about dag parsing summary.
        This is called once every time around the parsing "loop" - i.e. after
        all files have been parsed.
        """
        parse_time = time.perf_counter() - self._parsing_start_time
        Stats.gauge("dag_processing.total_parse_time", parse_time)
        Stats.gauge("dagbag_size", sum(stat.num_dags for stat in self._file_stats.values()))
        Stats.gauge(
            "dag_processing.import_errors", sum(stat.import_errors for stat in self._file_stats.values())
        )
    @property
    def file_paths(self):
        return self._file_paths