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Histograms with bucket labels starting with '-' are missing _sum metric in 0.8.0? #552
Description
I have encountered an issue with my metrics after having upgraded from version 0.7.1 to 0.8.0.
In the example below, the resulting histogram does not have the sum metric (suffix _sum) when using 0.8.0. If I use version 0.7.1, the _sum metric is back.
label_values = ['1', 'DKK']
bucket_values = [['-50000', 40], ['+Inf', 40]]
buckets_sum = 3000.0
h = HistogramMetricFamily(name, desc, labels=label_names)
h.add_metric(label_values, bucket_values, buckets_sum)
yield h
If I change the value of the 1st bucket, so it no longer has the minus/dash prefix (As seen below), the _sum metric is no longer missing in when using version 0.8.0.
bucket_values = [['50000', 40], ['+Inf', 40]]
Is this behaviour a feature (Which I do not understand) or a regression?
Thanks,
Tobias
Activity
brian-brazil commentedon May 28, 2020
This is correct, negative observations means that sum would no longer be a counter and it is thus excluded as per OpenMetrics.
tobiasbp commentedon May 28, 2020
Counter = never decreasing (AFAIK). Makes sense. Thanks for all your work on Prometheus.
belm0 commentedon Feb 26, 2021
@brian-brazil then it's an OpenMetrics flaw that histogram "_sum" is of type counter. It should be a gauge, and therefore support histograms with negative observations.
How do you propose we derive the average from a histogram metric? It should be simply _sum / _count.