Multiple system metrics return negative values when using DELTA temporality.

[bjrara]

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Describe your environment

OS: CentOS Python version: 3.9.16 Package version: OTEL 1.25.0

What happened?

The following metrics are found with negative values when configuring to export using DELTA temporality.

• system.network.connections
• process.runtime.cpython.gc_count
• process.runtime.cpython.memory
• process.runtime.cpython.thread_count

Steps to Reproduce

temporality_dict: Dict[type, AggregationTemporality] = {}
for typ in [
    Counter,
    UpDownCounter,
    ObservableCounter,
    ObservableCounter,
    ObservableUpDownCounter,
    ObservableGauge,
    Histogram,
]:
    temporality_dict[typ] = AggregationTemporality.DELTA

set_meter_provider(MeterProvider([PeriodicExportingMetricReader(ConsoleMetricExporter(preferred_temporality=temporality_dict))], resource=resource))
SystemMetricsInstrumentor().instrument()

Expected Result

Metrics generated with non-negative value

Actual Result

Metrics generated with negative value

Additional context

Sep 11 03:35:10: Descriptor:
Sep 11 03:35:10:      -> Name: process.runtime.cpython.memory
Sep 11 03:35:10:      -> Description: Runtime cpython memory
Sep 11 03:35:10:      -> Unit: bytes
Sep 11 03:35:10:      -> DataType: Sum
Sep 11 03:35:10:      -> IsMonotonic: false
Sep 11 03:35:10:      -> AggregationTemporality: Delta
Sep 11 03:35:10: NumberDataPoints #0
Sep 11 03:35:10: Data point attributes:
Sep 11 03:35:10:      -> type: Str(rss)
Sep 11 03:35:10: StartTimestamp: 2024-09-11 03:34:09.999252322 +0000 UTC
Sep 11 03:35:10: Timestamp: 2024-09-11 03:35:10.010880332 +0000 UTC
Sep 11 03:35:10: Value: -1081344
Sep 11 03:35:10: NumberDataPoints #1
Sep 11 03:35:10: Data point attributes:
Sep 11 03:35:10:      -> type: Str(vms)
Sep 11 03:35:10: StartTimestamp: 2024-09-11 03:34:09.999252322 +0000 UTC
Sep 11 03:35:10: Timestamp: 2024-09-11 03:35:10.010880332 +0000 UTC
Sep 11 03:35:10: Value: -1048576

Would you like to implement a fix?

Yes