Fill _kwargs attribute

[Strady]

Problem description

When the labels method is called a new instance of Summary is created inside and this new instance uses default values for invariants, max_age_seconds and age_buckets instead of those were passed for the "parent" Summary instance initialization.

Here is a snippet from the labels method where new Summary instance is created. self._kwargs here is empty, so no invariants, max_age_seconds and age_buckets are passed to __init__:

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
    )

Example

s = Summary(
    "request_latency_seconds", 
    "Description of summary",
    invariants=((0.95, 0.005), (0.99, 0.001))
)
s.labels(method="GET", endpoint="/profile").observe(1.2)
s.labels(method="POST", endpoint="/login").observe(3.4)

In this example both observations are done with the DEFAULT_INVARIANTS.

Solution

The way it's handled for example in the Histogram class is just to put buckets in self._kwargs after the super class initialization. Apparently for the Summary the same should be done for the invariants, max_age_seconds and age_buckets:

def __init__(
    ...
) -> None:
    self._invariants = invariants
    self._max_age_seconds = max_age_seconds
    self._age_buckets = age_buckets
    self._lock = Lock()
    super().__init__(
        name,
        documentation,
        labelnames=labelnames,
        namespace=namespace,
        subsystem=subsystem,
        unit=unit,
        registry=registry,
        _labelvalues=_labelvalues,
    )
    self._kwargs['invariants'] = invariants
    self._kwargs['max_age_seconds'] = max_age_seconds
    self._kwargs['age_buckets'] = age_buckets

[antonmyronyuk]

Thank you for contribution!

Released: https://pypi.org/project/prometheus-summary/0.1.3/

[Strady]

Thank you for contribution!

Released: https://pypi.org/project/prometheus-summary/0.1.3/

Awesome! Thanks for the fast merge