Azure Monitor exporter exports metric values always as 0 for long counter measurements

[bastbu]

Component(s)

exporter/azuremonitor

What happened?

Description

When using the Azure Monitor exporter to export metrics using the OTLP exporter, the customMetrics showing up in application insights always have value: 0.

Steps to Reproduce

Can be reproduced by taking measurements (e.g. from a counter) in a .NET application:

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

namespace Test;

public class Program
{
    private static readonly Meter MyMeter = new("Test", "1.0");
    private static readonly Counter<long> MyFruitCounter = MyMeter.CreateCounter<long>("MyFruitCounter");

    public static void Main()
    {
        using var meterProvider = Sdk.CreateMeterProviderBuilder()
            .AddMeter("Test")
            .AddOtlpExporter()
            .AddConsoleExporter()
            .Build();

        MyFruitCounter.Add(10, new("name", "apple"), new("color", "red"));
    }
}

Expected Result

As per the above example, the value field should be 10 (given a valueCount of 1).

Actual Result

The value, valueMin, valueMax and valueSum fields are all 0:

The console exporter on the test application displays the value to be 10, which is correct:

Resource associated with Metric:
    service.name: unknown_service:dotnet

Export MyFruitCounter, Meter: Test/1.0
(2023-02-24T09:54:09.9409890Z, 2023-02-24T09:54:10.1143793Z] color: red name: apple LongSum
Value: 10

Collector version

0.72.0

Environment information

Environment

OS: WSL2 on Windows 11

OpenTelemetry Collector configuration

receivers:
  otlp:
    protocols: 
      grpc:
processors:
exporters:
  logging:
  azuremonitor:
    instrumentation_key: <redacted>
service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: []
      exporters: [logging,azuremonitor]
    metrics:
      receivers: [otlp]
      processors: []
      exporters: [logging,azuremonitor]
    logs:
      receivers: [otlp]
      processors: []
      exporters: [logging,azuremonitor]

Log output

No response

Additional context

No response

[github-actions]

Pinging code owners:

• exporter/azuremonitor: @pcwiese

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[bastbu]

After looking at the source code, my guess is that this is a consequence of only using numberDataPoint.DoubleValue() in

opentelemetry-collector-contrib/exporter/azuremonitorexporter/metric_to_envelopes.go

Line 133 in 7206d6d

dataPoint.Value = numberDataPoint.DoubleValue()

Any IntValue() will be discarded, which might be why for the above sample code (which uses Counter<long>) the value in Application Insights is 0. If wanted, I can work on a fix for this.