Metric for label set has incorrect name exposed in multiprocess mode

The following piece of code from the metrics.py

        with self._lock:
            if labelvalues not in self._metrics:
                self._metrics[labelvalues] = self.__class__(
                    self._name,
                    documentation=self._documentation,
                    labelnames=self._labelnames,
                    unit=self._unit,
                    _labelvalues=labelvalues,
                    **self._kwargs
                )

passes the self._name as name parameter in the ctor. The problem is that at this point self._name is actually a full name created by _build_full_name(), for example mynamespace_mysubsystem_mymetric_myunit. Unfortunately, this name undergoes a second round of full name construction. In case of default ctor, where namespace, subsystem and unit all have str = '' default value, this is not a big deal. But if a library user has custom ctor with non-empty default values it causes a pretty weird name to be produced:

mydefaultnamespace_mydefaultsubsystem_mynamespace_mysubsystem_mymetric_myunit_mydefaultunit

Now, in non-multiprocess mode this is not a problem as collector takes the metric name from the parent metric and simply append the child metric labels and values. But multiprocess collector takes what is present in the process files, and those have child metric names.

Commencez dans metrics.py, autour des lignes 201-210, et suivez la manière dont les noms des métriques enfants sont écrits pour le multiprocess collector. Reproduisez le cas avec des valeurs par défaut non vides pour namespace, subsystem et unit, puis vérifiez que le nom de la métrique du fichier de processus n'est pas construit deux fois et correspond au nom complet attendu.