**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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"""
        Retrieve the last completion time for processing a specific path.
        :param file_path: the path to the file that was processed
        :return: the finish time of the process of the last run, or None if the
            file was never processed.
        """
        stat = self._file_stats.get(file_path)
        return stat.last_finish_time if stat else None
    def get_start_time(self, file_path) -> datetime | None:
        """
        Retrieve the last start time for processing a specific path.
        :param file_path: the path to the file that's being processed
        :return: the start time of the process that's processing the
            specified file or None if the file is not currently being processed
        """
        if file_path in self._processors:
            return self._processors[file_path].start_time
        return None
    def get_run_count(self, file_path) -> int:
        """
        The number of times the given file has been parsed.
        :param file_path: the path to the file that's being processed
        """
        stat = self._file_stats.get(file_path)
        return stat.run_count if stat else 0
    def get_dag_directory(self) -> str: