PeriodicMetricExporter does not export periodically for either Delta or Cumulative temporality ExponentialHistogram

Describe your environment

OS: Centos 7
Python version: 3.11.1
SDK version: 1.25.0
API version: 1.25.0

What happened?

I have a low-throughput service and have implemented my own Histogram to measure the duration of an operation. This uses a PeriodicMetricExporter which is configured to export every 60 seconds. When I use Delta temporality, I get an export within 60 seconds of the last histogram recording. I then have no exports until the next observation is made.

When changing to Cumulative temporality I have the exact same experience. For comparison purposes, when using the Golang SDK I get the same behaviour as Python's Delta but, when using Cumulative, I get a metronomic export every 60 seconds regardless of any observations being recorded..

Should the Python PeriodicMetricExporter export every 60 seconds or not, and how does temporality setting play into it? At the moment it causes me a problem because my service has low throughput. My observability backend (New Relic) uses the StartTimeUnixNano value which can be hours in the past. A constant periodic export would help to correct this as the StartTimeUnixNano would be at most 60 seconds in the past.

Steps to Reproduce

metrics_temporality = {
        Histogram: AggregationTemporality.DELTA
    }
otlp_metric_exporter = OTLPMetricExporter(endpoint=grpc_collector_address, insecure=True,
                                              preferred_temporality=metrics_temporality, timeout=30_000)
metric_reader = PeriodicExportingMetricReader(otlp_metric_exporter,
                                                  export_interval_millis=60_000))
meter_provider = MeterProvider(metric_readers=[metric_reader], resource=_create_resources(),
                                   views=[View(instrument_type=Histogram,
                                               aggregation=ExponentialBucketHistogramAggregation())])
metrics.set_meter_provider(meter_provider)

meter = metrics.get_meter(__name__)

h = meter.create_histogram(
        name='my_histogram', unit='s', description='just my histogram'
    )

h.record(1.0)
time.sleep(120)
h.record(2.0)

Expected Result

I expected to see periodic metric exports for the histogram every 60 seconds, regardless of chosen temporality

Actual Result

A metric export within 60 seconds of the last observation.

Additional context

N/A

Would you like to implement a fix?

None

@ocelotl

@ocelotl

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

SDK 1.26.0 includes the fix for this cumulative exponential histogram case in #3978, released July 25, 2024.

My Codex agent executed this example on Python 3.12.10, using SDK 1.25.0 and 1.26.0 with their matching API and semantic conventions. It records once, then collects twice.

from opentelemetry.sdk.metrics import MeterProvider
from opentelemetry.sdk.metrics._internal.instrument import Histogram
from opentelemetry.sdk.metrics.export import AggregationTemporality, InMemoryMetricReader
from opentelemetry.sdk.metrics.view import ExponentialBucketHistogramAggregation, View

reader = InMemoryMetricReader(
    preferred_temporality={Histogram: AggregationTemporality.CUMULATIVE}
)
provider = MeterProvider(
    metric_readers=[reader],
    views=[View(instrument_type=Histogram, aggregation=ExponentialBucketHistogramAggregation())],
)
histogram = provider.get_meter("repro3971").create_histogram("duration")
histogram.record(1.0)
try:
    for _ in range(2):
        data = reader.get_metrics_data()
        print([
            point.count
            for resource in data.resource_metrics
            for scope in resource.scope_metrics
            for metric in scope.metrics
            for point in metric.data.data_points
        ] if data else [])
finally:
    provider.shutdown()

SDK 1.25.0: [1], []
SDK 1.26.0: [1], [1]

With PeriodicExportingMetricReader and an in-memory recording exporter, the agent also observed three cumulative exports after one observation on 1.26.0 and current main (bc3bd9ce). Cumulative StartTimeUnixNano stayed constant across those exports; repeated export does not move the cumulative start time forward.

The New Relic path was not exercised. For the missing cumulative exports, try SDK 1.26.0 or later with AggregationTemporality.CUMULATIVE.

Assisted with Claude Code; I checked and edited it.

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PeriodicMetricExporter does not export periodically for either Delta or Cumulative temporality ExponentialHistogram #3971

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What happened?

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Expected Result

Actual Result

Additional context

Would you like to implement a fix?

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PeriodicMetricExporter does not export periodically for either Delta or Cumulative temporality ExponentialHistogram #3971

Description

Describe your environment

What happened?

Steps to Reproduce

Expected Result

Actual Result

Additional context

Would you like to implement a fix?

Activity

aabmass commented on Jun 14, 2024

mertefesensoy commented on Nov 1, 2026

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