Histogram does not support negative buckets #782

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1. csmarchbanks commented on Mar 11, 2022

   

   csmarchbanks

   on Mar 11, 2022

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   Hmm, could I get a bit more detail on how they are not supported/an example or failing test? The very brief tests I am running everything seems to work ok. We certainly aim to support negative buckets!

   Note that I don't think -Inf should be be added as it doesn't make any sense for a value to be less than or equal to -Inf. Also, according to the Open Metrics spec, in the presence of negative histogram buckets _sum MUST be omitted, and that is how it is handled by this library.
2. baryluk commented on Mar 15, 2022

   

   baryluk

   on Mar 15, 2022

   Last edited by baryluk

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   Yes, -Inf doesn't make much sens probably.

   But here is an example of the failure:

   #!/usr/bin/env python3
   
   from prometheus_client import Histogram
   
   buckets = [-100, -10, -5, 0, 5, 10, 100]
   
   h = Histogram('h', '', buckets=buckets)
   h.observe(6)
   print(h.collect())

   [Metric(h, , histogram, , [
   Sample(name='h_bucket', labels={'le': '-100.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '-10.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '-5.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '0.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '5.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '10.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '100.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '+Inf'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_count', labels={}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_created', labels={}, value=1647348798.9148076, timestamp=None, exemplar=None)])]
   

   Notice value=0.0 for non-positive buckets.
3. baryluk commented on Mar 15, 2022

   

   baryluk

   on Mar 15, 2022

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   My bad. It actually works:

   h.observe(-60)

   [Metric(h, , histogram, , [
   Sample(name='h_bucket', labels={'le': '-100.0'}, value=0.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '-10.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '-5.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '0.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '5.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '10.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '100.0'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_bucket', labels={'le': '+Inf'}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_count', labels={}, value=1.0, timestamp=None, exemplar=None),
   Sample(name='h_created', labels={}, value=1647348909.1770196, timestamp=None, exemplar=None)])]
   

   My bad.
4. baryluk

   closed this as completedon Mar 15, 2022