Gauge read at startup then disapears

Describe your environment

OS: debian
Python version: 3.11.2
SDK version: 1.31 & 1.24
API version: 1.31 & 1.24

What happened?

I expect the following code to show both gauge & counter every 1s in the console (or when scrapped by prometheus client) but it does not. counter is always there. gauge is there when launching the script (very first seconds) then disapears.


import random
import time

from prometheus_client import start_http_server

from opentelemetry.exporter.prometheus import PrometheusMetricReader
from opentelemetry.metrics import get_meter_provider, set_meter_provider
from opentelemetry.sdk.metrics import MeterProvider
from opentelemetry.sdk.metrics.export import (
    ConsoleMetricExporter,
    PeriodicExportingMetricReader,
)

# Start Prometheus client
start_http_server(port=8000, addr="0.0.0.0")
# Exporter to export metrics to Prometheus
prefix = "MyAppPrefix"
reader = PrometheusMetricReader(prefix)
reader2 = PeriodicExportingMetricReader(ConsoleMetricExporter(), export_interval_millis=1_000)
# Meter is responsible for creating and recording metrics
set_meter_provider(MeterProvider(metric_readers=[reader, reader2]))
meter = get_meter_provider().get_meter("view-name-change", "0.1.2")

my_counter = meter.create_counter("my.counter")
my_gauge = meter.create_gauge("my.gauge")

while 1:
    my_gauge.set(random.randint(1, 10))
    my_counter.add(random.randint(1, 10))
    time.sleep(61)

Steps to Reproduce

run the script above

Expected Result

gauge to be exported properly

Actual Result

gauge is not exported properly

Additional context

No response

Would you like to implement a fix?

No

This is the expected behavior no? Like, gauge uses LastValueAggregation, it will be exported when you have a new value to export, like when you call gauge.set() again

@Filigran-Automation

Hi @Filigran-Automation -- have you looked at using an ObservableGauge instead?

This is the expected behavior no? Like, gauge uses LastValueAggregation, it will be exported when you have a new value to export, like when you call gauge.set() again

I think it's contrary to otel specification and should be fixed: https://opentelemetry.io/docs/specs/otel/metrics/sdk/?utm_source=chatgpt.com#metricreader

For synchronous instruments with Cumulative aggregation temporality, MetricReader.Collect MUST receive data points exposed in previous collections regardless of whether new measurements have been recorded.

Cumulative is the default temporality

This is the expected behavior no? Like, gauge uses LastValueAggregation, it will be exported when you have a new value to export, like when you call gauge.set() again

I think it's contrary to otel specification and should be fixed: https://opentelemetry.io/docs/specs/otel/metrics/sdk/?utm_source=chatgpt.com#metricreader

For synchronous instruments with Cumulative aggregation temporality, MetricReader.Collect MUST receive data points exposed in previous collections regardless of whether new measurements have been recorded.

Cumulative is the default temporality

hmmm. Indeed, this should be fixed then. Just checked go-sdk and it retains the last value for synchronous instruments when the reader uses cumulative temporality

A simple test that fails at main if useful. Thanks and feel free to open a PR

    def test_cumulative_gauge_multiple_collect(self):
        reader = InMemoryMetricReader()
        meter = MeterProvider(metric_readers=[reader]).get_meter("test_meter")
        gauge = meter.create_gauge("gauge")
        gauge.set(1)
        metrics_data_0 = reader.get_metrics_data()
        metrics_data_1 = reader.get_metrics_data()
        self.assertIsNotNone(metrics_data_0)
        self.assertIsNotNone(metrics_data_1)
        data_point_0 = metrics_data_0.resource_metrics[0].scope_metrics[0].metrics[0].data.data_points[0]
        data_point_1 = metrics_data_1.resource_metrics[0].scope_metrics[0].metrics[0].data.data_points[0]
        self.assertEqual(data_point_0.value, data_point_1.value)

fix(opentelemetry-sdk): keep synchronous gauge values across cumulati…

@emdneto

@emdneto Here it is! #5637

I was also unsure if it's a bug since Gauge points don't have a temporality, but taking a closer look at the spec it's pretty clear (emphasis added)

For synchronous instruments with Cumulative aggregation temporality, MetricReader.Collect MUST receive data points exposed in previous collections regardless of whether new measurements have been recorded. [...] These rules apply to all metrics, not just those whose point kinds includes an aggregation temporality field.

fix(opentelemetry-sdk): keep synchronous gauge values across cumulati…

Navigation Menu

Repository navigation

Gauge read at startup then disapears #4512

Describe your environment

What happened?

Steps to Reproduce

Expected Result

Actual Result

Additional context

Would you like to implement a fix?

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Gauge read at startup then disapears #4512

Description

Describe your environment

What happened?

Steps to Reproduce

Expected Result

Actual Result

Additional context

Would you like to implement a fix?

Activity

emdneto commented on Apr 3, 2025

pmcollins commented on Apr 7, 2025

kacper-wolkiewicz-reef commented on Sep 4, 2026

emdneto commented on Sep 4, 2026

kacper-wolkiewicz-reef commented on Sep 7, 2026

aabmass commented on Sep 10, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions