Base2 Exponential Bucket Histogram should reset to scale 20 after each collection cycle if DELTA aggregation temporality is used

[reyang]

Package

OpenTelemetry

Package Version

Package Name	Version
OpenTelemetry.Api	1.8.0
OpenTelemetry	1.8.0

Runtime Version

all

Description

opentelemetry-dotnet/src/OpenTelemetry/Metrics/Base2ExponentialBucketHistogram.cs

Lines 202 to 203 in 6c0327c

	// TODO: Determine if this is sufficient for delta temporality.
	// I'm not sure we should be resetting the scale.

It should reset, otherwise the precision will never recover unless the process restarted.

Steps to Reproduce

using System.Diagnostics.Metrics;
using OpenTelemetry;
using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;

namespace CustomizingTheSdk;

public class Program
{
    private static readonly Meter Meter1 = new("CompanyA.ProductA.Library1", "1.0");

    public static void Main()
    {
        using var meterProvider = Sdk.CreateMeterProviderBuilder()
            .AddMeter(Meter1.Name)
            .AddView(instrumentName: "MyExponentialBucketHistogram", new Base2ExponentialBucketHistogramConfiguration())
            .AddConsoleExporter((_, readerOptions) => readerOptions.TemporalityPreference = MetricReaderTemporalityPreference.Delta)
            .Build();

        var random = new Random();

        var exponentialBucketHistogram = Meter1.CreateHistogram<long>("MyExponentialBucketHistogram");
        for (int i = 0; i < 20000; i++)
        {
            exponentialBucketHistogram.Record(random.Next(1, 1000), new("tag1", "value1"), new("tag2", "value2"));
        }

        meterProvider.ForceFlush();
    
        exponentialBucketHistogram.Record(2, new("tag1", "value1"), new("tag2", "value2"));
    }
}

Expected Result

The 2nd export batch should have low dynamic range and high precision (scale = 20) since Delta Temporality is used.

Actual Result

The 2nd export batch has a large dynamic range (0.0.9170040432046712, 1024] and low precision, which was carried from the 1st export.

Resource associated with Metric:
    telemetry.sdk.name: opentelemetry
    telemetry.sdk.language: dotnet
    telemetry.sdk.version: 1.8.1-alpha.0.75
    service.name: unknown_service:customizing-the-sdk

Metric Name: MyExponentialBucketHistogram, Meter: CompanyA.ProductA.Library1/1.0
(2024-05-21T04:32:29.6575560Z, 2024-05-21T04:32:29.6881729Z] tag1: value1 tag2: value2 ExponentialHistogram
Value: Sum: 9953662 Count: 20000 Min: 1 Max: 999
(0.9170040432046712, 1]:25
(1, 1.0905077326652577]:0
(1.0905077326652577, 1.189207115002721]:0
(1.189207115002721, 1.2968395546510096]:0
(1.2968395546510096, 1.414213562373095]:0
(1.414213562373095, 1.5422108254079407]:0
(1.5422108254079407, 1.681792830507429]:0
(1.681792830507429, 1.8340080864093424]:0
(1.8340080864093424, 2]:18
(2, 2.1810154653305154]:0
(2.1810154653305154, 2.378414230005442]:0
(2.378414230005442, 2.5936791093020193]:0
(2.5936791093020193, 2.82842712474619]:0
(2.82842712474619, 3.0844216508158815]:17
(3.0844216508158815, 3.363585661014858]:0
(3.363585661014858, 3.668016172818685]:0
(3.668016172818685, 4]:16
(4, 4.362030930661031]:0
(4.362030930661031, 4.756828460010884]:0
(4.756828460010884, 5.187358218604039]:18
(5.187358218604039, 5.656854249492381]:0
(5.656854249492381, 6.168843301631763]:25
(6.168843301631763, 6.727171322029717]:0
(6.727171322029717, 7.33603234563737]:11
(7.33603234563737, 7.999999999999998]:19
(7.999999999999998, 8.724061861322062]:0
(8.724061861322062, 9.513656920021766]:16
(9.513656920021766, 10.374716437208079]:25
(10.374716437208079, 11.31370849898476]:20
(11.31370849898476, 12.337686603263528]:17
(12.337686603263528, 13.454342644059432]:25
(13.454342644059432, 14.672064691274741]:18
(14.672064691274741, 15.999999999999998]:40
(15.999999999999998, 17.448123722644116]:24
(17.448123722644116, 19.027313840043536]:40
(19.027313840043536, 20.749432874416147]:16
(20.749432874416147, 22.62741699796952]:32
(22.62741699796952, 24.67537320652705]:53
(24.67537320652705, 26.908685288118864]:37
(26.908685288118864, 29.344129382549472]:73
(29.344129382549472, 32]:66
(32, 34.89624744528824]:44
(34.89624744528824, 38.05462768008707]:82
(38.05462768008707, 41.4988657488323]:60
(41.4988657488323, 45.254833995939045]:75
(45.254833995939045, 49.3507464130541]:86
(49.3507464130541, 53.817370576237735]:81
(53.817370576237735, 58.68825876509898]:90
(58.68825876509898, 63.99999999999998]:136
(63.99999999999998, 69.79249489057648]:98
(69.79249489057648, 76.10925536017416]:142
(76.10925536017416, 82.99773149766457]:132
(82.99773149766457, 90.50966799187806]:164
(90.50966799187806, 98.70149282610821]:142
(98.70149282610821, 107.63474115247547]:174
(107.63474115247547, 117.37651753019786]:212
(117.37651753019786, 127.99999999999997]:205
(127.99999999999997, 139.58498978115298]:228
(139.58498978115298, 152.21851072034832]:249
(152.21851072034832, 165.99546299532915]:259
(165.99546299532915, 181.01933598375612]:353
(181.01933598375612, 197.40298565221642]:325
(197.40298565221642, 215.26948230495097]:350
(215.26948230495097, 234.75303506039575]:378
(234.75303506039575, 255.99999999999994]:419
(255.99999999999994, 279.16997956230597]:487
(279.16997956230597, 304.4370214406964]:505
(304.4370214406964, 331.99092599065835]:519
(331.99092599065835, 362.0386719675123]:631
(362.0386719675123, 394.8059713044329]:655
(394.8059713044329, 430.5389646099016]:750
(430.5389646099016, 469.5060701207915]:735
(469.5060701207915, 511.99999999999994]:853
(511.99999999999994, 558.339959124612]:934
(558.339959124612, 608.8740428813928]:993
(608.8740428813928, 663.9818519813167]:1165
(663.9818519813167, 724.0773439350246]:1228
(724.0773439350246, 789.6119426088659]:1309
(789.6119426088659, 861.0779292198033]:1403
(861.0779292198033, 939.0121402415831]:1561
(939.0121402415831, 1024]:1137


Metric Name: MyExponentialBucketHistogram, Meter: CompanyA.ProductA.Library1/1.0
(2024-05-21T04:32:29.6881729Z, 2024-05-21T04:32:29.7153904Z] tag1: value1 tag2: value2 ExponentialHistogram
Value: Sum: 2 Count: 1 Min: 2 Max: 2
(0.9170040432046712, 1]:0
(1, 1.0905077326652577]:0
(1.0905077326652577, 1.189207115002721]:0
(1.189207115002721, 1.2968395546510096]:0
(1.2968395546510096, 1.414213562373095]:0
(1.414213562373095, 1.5422108254079407]:0
(1.5422108254079407, 1.681792830507429]:0
(1.681792830507429, 1.8340080864093424]:0
(1.8340080864093424, 2]:1
(2, 2.1810154653305154]:0
(2.1810154653305154, 2.378414230005442]:0
(2.378414230005442, 2.5936791093020193]:0
(2.5936791093020193, 2.82842712474619]:0
(2.82842712474619, 3.0844216508158815]:0
(3.0844216508158815, 3.363585661014858]:0
(3.363585661014858, 3.668016172818685]:0
(3.668016172818685, 4]:0
(4, 4.362030930661031]:0
(4.362030930661031, 4.756828460010884]:0
(4.756828460010884, 5.187358218604039]:0
(5.187358218604039, 5.656854249492381]:0
(5.656854249492381, 6.168843301631763]:0
(6.168843301631763, 6.727171322029717]:0
(6.727171322029717, 7.33603234563737]:0
(7.33603234563737, 7.999999999999998]:0
(7.999999999999998, 8.724061861322062]:0
(8.724061861322062, 9.513656920021766]:0
(9.513656920021766, 10.374716437208079]:0
(10.374716437208079, 11.31370849898476]:0
(11.31370849898476, 12.337686603263528]:0
(12.337686603263528, 13.454342644059432]:0
(13.454342644059432, 14.672064691274741]:0
(14.672064691274741, 15.999999999999998]:0
(15.999999999999998, 17.448123722644116]:0
(17.448123722644116, 19.027313840043536]:0
(19.027313840043536, 20.749432874416147]:0
(20.749432874416147, 22.62741699796952]:0
(22.62741699796952, 24.67537320652705]:0
(24.67537320652705, 26.908685288118864]:0
(26.908685288118864, 29.344129382549472]:0
(29.344129382549472, 32]:0
(32, 34.89624744528824]:0
(34.89624744528824, 38.05462768008707]:0
(38.05462768008707, 41.4988657488323]:0
(41.4988657488323, 45.254833995939045]:0
(45.254833995939045, 49.3507464130541]:0
(49.3507464130541, 53.817370576237735]:0
(53.817370576237735, 58.68825876509898]:0
(58.68825876509898, 63.99999999999998]:0
(63.99999999999998, 69.79249489057648]:0
(69.79249489057648, 76.10925536017416]:0
(76.10925536017416, 82.99773149766457]:0
(82.99773149766457, 90.50966799187806]:0
(90.50966799187806, 98.70149282610821]:0
(98.70149282610821, 107.63474115247547]:0
(107.63474115247547, 117.37651753019786]:0
(117.37651753019786, 127.99999999999997]:0
(127.99999999999997, 139.58498978115298]:0
(139.58498978115298, 152.21851072034832]:0
(152.21851072034832, 165.99546299532915]:0
(165.99546299532915, 181.01933598375612]:0
(181.01933598375612, 197.40298565221642]:0
(197.40298565221642, 215.26948230495097]:0
(215.26948230495097, 234.75303506039575]:0
(234.75303506039575, 255.99999999999994]:0
(255.99999999999994, 279.16997956230597]:0
(279.16997956230597, 304.4370214406964]:0
(304.4370214406964, 331.99092599065835]:0
(331.99092599065835, 362.0386719675123]:0
(362.0386719675123, 394.8059713044329]:0
(394.8059713044329, 430.5389646099016]:0
(430.5389646099016, 469.5060701207915]:0
(469.5060701207915, 511.99999999999994]:0
(511.99999999999994, 558.339959124612]:0
(558.339959124612, 608.8740428813928]:0
(608.8740428813928, 663.9818519813167]:0
(663.9818519813167, 724.0773439350246]:0
(724.0773439350246, 789.6119426088659]:0
(789.6119426088659, 861.0779292198033]:0
(861.0779292198033, 939.0121402415831]:0
(939.0121402415831, 1024]:0

Additional Context

No response