Prometheus exporter does not cumulatively sum histogram buckets

[albertlockett]

Description

Using the otel-go sdk to collect metrics with prometheus exporter does report the values in the bucket as a cumulative sum of the value for this bucket and the buckets of lower values.

If I do this:

	histogram, _ := meter.SyncInt64().Histogram("my-histogram")
	histogram.Record(ctx, 95)
	histogram.Record(ctx, 95)
	histogram.Record(ctx, 95)
	histogram.Record(ctx, 245)
	histogram.Record(ctx, 245)
	histogram.Record(ctx, 495)

I get an output like this:

$ curl -XGET http://localhost:2222/metrics                                     
...
my_histogram_bucket{le="100"} 3
my_histogram_bucket{le="250"} 2
my_histogram_bucket{le="500"} 1
my_histogram_bucket{le="1000"} 0
...
my_histogram_bucket{le="+Inf"} 6

Environment

• OS: osx
• Architecture: intel
• Go Version: 1.19
• opentelemetry-go version:

Steps To Reproduce

here's a project that will reproduce
https://github.com/albertlockett/otel-go-metrics-test01/blob/main/go.mod

Expected behavior

I was expecting an output like this (this is the behaviour I get from opentelemetry-js)

my_histogram_bucket{le="100"} 3
my_histogram_bucket{le="250"} 5
my_histogram_bucket{le="500"} 6
my_histogram_bucket{le="1000"} 6
my_histogram_bucket{le="+Inf"} 6

[albertlockett]

#3282

[dangermike]

I have seen the same behavior, including with the provided example code from /example/prometheus/main.go.

Thanks, @albertlockett!