[Bug]: f64_counter can be decremented

[elpis-furiosa]

What happened?

I was experimenting with OpenTelemetry Counters and found out that it is possible to decrement the value of f64 counters. The bug can be reproduced with this code:

use std::thread;
use std::time::Duration;

use opentelemetry::metrics::MeterProvider;
use opentelemetry_sdk::metrics::SdkMeterProvider;

fn main() {

    let exporter = opentelemetry_stdout::MetricExporterBuilder::default()
        .build();

    let meter_provider = SdkMeterProvider::builder()
        .with_periodic_exporter(exporter)
        .build();

    let meter = meter_provider.meter("test_meter");

    let counter = meter.f64_counter("test_counter").build();

    let mut taskset = Vec::new();

    taskset.push(thread::spawn(move || {
        for i in 0..100 {
            let value = if i % 2 == 0 {
                i as f64
            } else {
                -i as f64
            };
            counter.add(value, &[]);
            thread::sleep(Duration::from_secs(1));
        }
    }));

    for t in taskset {
        t.join().unwrap();
    }
}

OpenTelemetry API Version (i.e version of opentelemetry crate)

opentelemetry = { version = "0.30.0" , default-features = false, features = ["metrics"] }

OpenTelemetry SDK Version (i.e version of opentelemetry_sdk crate)

opentelemetry_sdk = { version = "0.30.0", default-features = false, features = ["experimental_metrics_custom_reader", "metrics"] }

What Exporter(s) are you seeing the problem on?

stdout

Relevant log output

Metrics
Resource
         ->  service.name=String(Static("unknown_service"))
         ->  telemetry.sdk.version=String(Static("0.30.0"))
         ->  telemetry.sdk.name=String(Static("opentelemetry"))
         ->  telemetry.sdk.language=String(Static("rust"))
        Instrumentation Scope #0
                Name         : test_meter
Metric #0
                Name         : test_counter
                Description  :
                Unit         :
                Type         : Sum
                Sum DataPoints
                Monotonic    : true
                Temporality  : Cumulative
                StartTime    : 2025-06-24 08:28:07.849672
                EndTime      : 2025-06-24 08:28:08.849881
                DataPoint #0
                        Value        : 0.0
                        Attributes   :
Metrics
Resource
         ->  service.name=String(Static("unknown_service"))
         ->  telemetry.sdk.version=String(Static("0.30.0"))
         ->  telemetry.sdk.name=String(Static("opentelemetry"))
         ->  telemetry.sdk.language=String(Static("rust"))
        Instrumentation Scope #0
                Name         : test_meter
Metric #0
                Name         : test_counter
                Description  :
                Unit         :
                Type         : Sum
                Sum DataPoints
                Monotonic    : true
                Temporality  : Cumulative
                StartTime    : 2025-06-24 08:28:07.849672
                EndTime      : 2025-06-24 08:28:09.850013
                DataPoint #0
                        Value        : -1.0
                        Attributes   :
Metrics
Resource
         ->  service.name=String(Static("unknown_service"))
         ->  telemetry.sdk.version=String(Static("0.30.0"))
         ->  telemetry.sdk.name=String(Static("opentelemetry"))
         ->  telemetry.sdk.language=String(Static("rust"))
        Instrumentation Scope #0
                Name         : test_meter
Metric #0
                Name         : test_counter
                Description  :
                Unit         :
                Type         : Sum
                Sum DataPoints
                Monotonic    : true
                Temporality  : Cumulative
                StartTime    : 2025-06-24 08:28:07.849672
                EndTime      : 2025-06-24 08:28:10.850155
                DataPoint #0
                        Value        : 1.0
                        Attributes   :

[Yooosless]

edit: add this to dependencies as well to recreate
opentelemetry-stdout = { version = "0.30.0", default-features = false, features = ["trace", "metrics", "logs"] }