Observable Counters/UpDownCounters Report Incorrect Values

[samin36]

Environment
Opentelemetry-cpp v1.9.0 on CentOS 7

Problem
Any Observable Counters/UpDownCounters report incorrect values if the initial observation value is non-zero.

Steps to reproduce

#include "opentelemetry/exporters/ostream/metric_exporter.h"
#include "opentelemetry/metrics/provider.h"
#include "opentelemetry/sdk/metrics/aggregation/default_aggregation.h"
#include "opentelemetry/sdk/metrics/aggregation/histogram_aggregation.h"
#include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader.h"
#include "opentelemetry/sdk/metrics/meter.h"
#include "opentelemetry/sdk/metrics/meter_provider.h"
#include <memory>
#include <thread>

namespace metric_sdk = opentelemetry::sdk::metrics;
namespace common = opentelemetry::common;
namespace exportermetrics = opentelemetry::exporter::metrics;
namespace metrics_api = opentelemetry::metrics;
namespace nostd = opentelemetry::nostd;

int value = 3;

void InitMetrics(const std::string &name) {
    std::unique_ptr<metric_sdk::PushMetricExporter> exporter{
        new exportermetrics::OStreamMetricExporter};

    std::string version{"1.2.0"};
    std::string schema{"https://opentelemetry.io/schemas/1.2.0"};

    // Initialize and set the global MeterProvider
    metric_sdk::PeriodicExportingMetricReaderOptions options;
    options.export_interval_millis = std::chrono::milliseconds(5000);
    options.export_timeout_millis = std::chrono::milliseconds(500);
    std::unique_ptr<metric_sdk::MetricReader> reader{
        new metric_sdk::PeriodicExportingMetricReader(std::move(exporter),
                                                      options)};
    auto provider = std::shared_ptr<metrics_api::MeterProvider>(
        new metric_sdk::MeterProvider());
    auto p = std::static_pointer_cast<metric_sdk::MeterProvider>(provider);
    p->AddMetricReader(std::move(reader));

    metrics_api::Provider::SetMeterProvider(provider);
}

void CleanupMetrics() {
    std::shared_ptr<metrics_api::MeterProvider> none;
    metrics_api::Provider::SetMeterProvider(none);
}

void TestCallback(opentelemetry::metrics::ObserverResult observer_result,
                  void * /* state */) {
    if (nostd::holds_alternative<nostd::shared_ptr<
            opentelemetry::metrics::ObserverResultT<int64_t>>>(
            observer_result)) {
        nostd::get<nostd::shared_ptr<
            opentelemetry::metrics::ObserverResultT<int64_t>>>(observer_result)
            ->Observe(value++);
    }
}

int main(int argc, char **argv) {
    std::string name{"ostream_metric_example"};
    InitMetrics(name);

    auto provider = metrics_api::Provider::GetMeterProvider();
    nostd::shared_ptr<metrics_api::Meter> meter =
        provider->GetMeter(name, "1.2.0");

    auto test_counter =
        meter->CreateInt64ObservableUpDownCounter("test_counter");
    test_counter->AddCallback(TestCallback, nullptr);

    while (true);

    CleanupMetrics();
}

What is the expected behavior?
The values are reported as 3, 4, 5, 6, etc.

{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:30 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 3
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}
{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:35 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 4
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}
{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:40 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 5
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}

What is the actual behavior?
The values are reported as 3, 7, 8, 9, etc.

{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:30 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 3
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}
{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:35 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 7
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}
{
  scope name    : ostream_metric_example
  schema url    :
  version       : 1.2.0
  start time    : Tue Sep  5 14:50:30 2023
  end time      : Tue Sep  5 14:50:40 2023
  instrument name       : test_counter
  description   :
  unit          :
  type          : SumPointData
  value         : 8
  attributes            :
  resources     :
        service.name: unknown_service
        telemetry.sdk.language: cpp
        telemetry.sdk.name: opentelemetry
        telemetry.sdk.version: 1.9.0
}

Additional Info
I tried to reproduce the same issue with:

• the Opentelemetry-Python SDK, but that reported the correct values (3, 4, 5, 6 etc.)
• Opentelemetry-cpp v1.11.0 and was able to successfully do so.

[lalitb]

Environment
Opentelemetry-cpp v1.9.0 on CentOS 7

Opentelemetry-cpp v1.11.0 and was able to successfully do so.

Do you mean you are seeing this issue with v1.9.0, and it works correctly in v1.11.0?

Ok please ignore it, I guess you mean the issue is there in v1.11.0 too. Will check further.