feat(sdk-metrics): implement metric reader metrics by anuraaga · Pull Request #6449 · open-telemetry/opentelemetry-js

anuraaga · 2026-02-26T06:19:11Z

Which problem is this PR solving?

I am helping to implement SDK internal metrics

https://opentelemetry.io/docs/specs/semconv/otel/sdk-metrics/

This implements metric reader metrics.

Implementation in Java - https://github.com/open-telemetry/opentelemetry-java/pull/8038/changes

/cc @trentm

Short description of the changes

Implement metrics for metric collections per semconv

Type of change

Please delete options that are not relevant.

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

Unit tests

Checklist:

Followed the style guidelines of this project
Unit tests have been added
Documentation has been updated

codecov · 2026-02-26T06:21:39Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.79%. Comparing base (8ee2a8b) to head (3f4c342).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6449      +/-   ##
==========================================
+ Coverage   95.76%   95.79%   +0.02%     
==========================================
  Files         375      378       +3     
  Lines       12739    12780      +41     
  Branches     3013     3020       +7     
==========================================
+ Hits        12200    12242      +42     
+ Misses        539      538       -1

Files with missing lines	Coverage Δ
...etry-exporter-prometheus/src/PrometheusExporter.ts	`96.73% <100.00%> (+0.03%)`	⬆️
...s/opentelemetry-exporter-prometheus/src/semconv.ts	`100.00% <100.00%> (ø)`
...imental/packages/opentelemetry-sdk-node/src/sdk.ts	`95.93% <ø> (ø)`
packages/opentelemetry-core/src/common/time.ts	`97.10% <100.00%> (+0.08%)`	⬆️
packages/sdk-metrics/src/MeterProvider.ts	`100.00% <100.00%> (ø)`
packages/sdk-metrics/src/export/MetricReader.ts	`100.00% <100.00%> (ø)`
...ages/sdk-metrics/src/export/MetricReaderMetrics.ts	`100.00% <100.00%> (ø)`
...etrics/src/export/PeriodicExportingMetricReader.ts	`100.00% <100.00%> (+1.26%)`	⬆️
packages/sdk-metrics/src/semconv.ts	`100.00% <100.00%> (ø)`

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anuraaga · 2026-02-26T06:21:41Z

    }

+    const collectDuration = hrTimeDuration(startTime, endTime);
+    const collectDurationSecs = collectDuration[0] + collectDuration[1] / 1e9;


Let me know if I missed something, I was surprised to not find hrTimeToSeconds since there are many metrics defined as seconds

I think it would be worthwhile adding hrTimeToSeconds to "packages/opentelemetry-core/src/common/time.ts". That could totally be in a separate PR, though. Or an issue would be welcome.

anuraaga · 2026-02-26T06:22:03Z

+ *   - Use a domain-specific attribute
+ *   - Set `error.type` to capture all errors, regardless of whether they are defined within the domain-specific set or not.
+ */
+export const ATTR_ERROR_TYPE = 'error.type' as const;


This one is actually stable but wasn't sure it's worth adding a dep on semconv for it

Understood. I don't have a strong opinion. If the semconv package was smaller we wouldn't hesistate to add the dep. :)

I imagine this usage will break attempts to use https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/scripts/gen-semconv-ts.js to re-generate this semconv.ts file, but that's not a real concern right now. That script is currently a best-effort helper and not mandated at all.

trentm · 2026-02-27T22:51:48Z

+ *   - Use a domain-specific attribute
+ *   - Set `error.type` to capture all errors, regardless of whether they are defined within the domain-specific set or not.
+ */
+export const ATTR_ERROR_TYPE = 'error.type' as const;


Understood. I don't have a strong opinion. If the semconv package was smaller we wouldn't hesistate to add the dep. :)

I imagine this usage will break attempts to use https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/scripts/gen-semconv-ts.js to re-generate this semconv.ts file, but that's not a real concern right now. That script is currently a best-effort helper and not mandated at all.

trentm · 2026-02-28T00:30:26Z

+    this._metrics = new MetricReaderMetrics(
+      OTEL_COMPONENT_TYPE_VALUE_PERIODIC_METRIC_READER,
+      meter
+    );


What about moving the MetricReaderMetrics instance to the MetricReader base class:

setMeterProvider moves to class MetricReader (and the method gets added to interface IMetricReader)

The setMeterProvider needs a value for otel.component.type, so a class extending MetricReader should be able to pass that in:

Add an optional otelComponentType string option to interface MetricReaderOptions

Get class PeriodicExportingMetricReader to pass in OTEL_COMPONENT_TYPE_VALUE_PERIODIC_METRIC_READER in its call to super()

Get class MetricReader to save that to private readonly _otelComponentType: string | undefined;

Get the implementation of setMeterProvider to use this._otelComponentType || this.constructor.name. This will allow a reasonable default value for MetricReader subclasses that don't fit one of the well-known names for otel.component.type. (From the spec: "otel.component.type: If none of the standardized values apply, implementations SHOULD use the language-defined name of the type. E.g. for Java the fully qualified classname SHOULD be used in this case.")

Move the handling for this._metrics.recordCollection(...) to MetricReader#collect().

Then it would also be good to update "experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusExporter.ts" to pass in otelComponentType: OTEL_COMPONENT_TYPE_VALUE_PROMETHEUS_HTTP_TEXT_METRIC_EXPORTER in its call to super()

Good idea that makes sense - did it and also the prometheus change. One deviation from this comment I resolved _otelComponentType to the automatic value in the constructor instead of setMeterProvider, let me know if I'm missing some JS intricacy that means that shouldn't be done.

trentm · 2026-02-28T00:33:08Z

    }

+    const collectDuration = hrTimeDuration(startTime, endTime);
+    const collectDurationSecs = collectDuration[0] + collectDuration[1] / 1e9;


I think it would be worthwhile adding hrTimeToSeconds to "packages/opentelemetry-core/src/common/time.ts". That could totally be in a separate PR, though. Or an issue would be welcome.

…y-js into metrics-reader-metrics

trentm

LGTM, modulo the changelog nit.

@pichlermarc Would you like to sanity check anything here? E.g. the addition of setMeterProvider to IMetricReader, perhaps. I'm not super-confident in the Metrics SDK.

…y-js into metrics-reader-metrics

anuraaga · 2026-04-02T03:25:44Z

Thanks @trentm - updated

pichlermarc · 2026-04-07T11:06:20Z

LGTM, modulo the changelog nit.

@pichlermarc Would you like to sanity check anything here? E.g. the addition of setMeterProvider to IMetricReader, perhaps. I'm not super-confident in the Metrics SDK.

I think the implementation looks solid - only issue I could see is that setMeterProvider() could prove confusing to users. For example somebody doing something like:

metrics.setGlobalMeterProvider(new MeterProvider());
const meterProvider = metrics.getMeterProvider();

const reader = new PeriodicExportingMetricReader({exporter: myExporter});
reader.setMeterProvider(meterProvider); // did not read the docs, why are no metrics exported?

I wonder if setSelfMonitoringMeterProvider() or another more descriptive name could help.

anuraaga · 2026-04-09T02:51:15Z

reader.setMeterProvider(meterProvider); // did not read the docs, why are no metrics exported?

That's a good point, thanks for bringing it up. In Java and Python, this method is actually private, either accessed by reflection or using Python's _ prefix naming scheme. Does it make sense to use a _ prefix here in JS too?

…y-js into metrics-reader-metrics

anuraaga · 2026-04-09T02:59:01Z

I think the use case for providing metrics for direct implementations of IMetricReader are low vs subclassing MetricReader. I reworked to remove from the interface and make the method _. Let me know if this seems reasonable, or I can revert it

…y-js into metrics-reader-metrics

anuraaga requested a review from a team as a code owner February 26, 2026 06:19

anuraaga force-pushed the metrics-reader-metrics branch from 4c1dd02 to 0e63817 Compare February 26, 2026 06:19

feat(metrics): implement metric reader metrics

5beee50

anuraaga force-pushed the metrics-reader-metrics branch from 0e63817 to 5beee50 Compare February 26, 2026 06:19

anuraaga commented Feb 26, 2026

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Chagnelog

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anuraaga changed the title ~~feat(metrics): implement metric reader metrics~~ feat(sdk-metrics): implement metric reader metrics Feb 26, 2026

trentm reviewed Feb 28, 2026

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anuraaga added 7 commits March 5, 2026 12:24

Merge branch 'main' of https://github.com/open-telemetry/opentelemetr…

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…y-js into metrics-reader-metrics

generify

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git add

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Lint

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Fix

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Update test

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Fix import

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anuraaga mentioned this pull request Mar 13, 2026

feat(metrics): implement metric reader metrics open-telemetry/opentelemetry-python#4970

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trentm approved these changes Mar 27, 2026

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Comment thread CHANGELOG.md Outdated

anuraaga added 2 commits April 2, 2026 12:07

Merge branch 'main' of https://github.com/open-telemetry/opentelemetr…

76e28bb

…y-js into metrics-reader-metrics

Update

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Merge branch 'main' into metrics-reader-metrics

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anuraaga added 3 commits April 9, 2026 11:52

Merge branch 'main' of https://github.com/open-telemetry/opentelemetr…

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…y-js into metrics-reader-metrics

Remove setMeterProvider from public API

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Underscore

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anuraaga added 2 commits April 16, 2026 14:21

Merge branch 'main' of https://github.com/open-telemetry/opentelemetr…

b7dd71e

…y-js into metrics-reader-metrics

Fix merge

3f4c342

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anuraaga commented Feb 26, 2026

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