Add OTLP HTTP MetricExporter max_export_batch_size by tammy-baylis-swi · Pull Request #4576 · open-telemetry/opentelemetry-python

tammy-baylis-swi · 2025-05-09T18:04:39Z

Description

Adds support for HTTP OTLPMetricExporter configurable max_export_batch_size, like the gRPC OTLPMetricExporter already does (completed through issue #2710 with PR #2809).

This is currently much longer than the gRPC version because:

HTTP protobuf representations of ResourceMetrics, ScopeMetrics, etc are not replace-able like the gRPC data classes
- So references are stored and new protobuf objects are created immediately before yield/export
protobuf does not define a DataPointT to encompass all metric types
- So I've added some if-elif throughout for accessing data points, creating new metrics objects

Fixes #4577

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

Added unit tests
Install OTLPMetricExporter locally and do the following:

Set up 3 counters, with add(1) calls to each
Init global MeterProvider using OTLPMetricExporter with max_export_batch_size=2 and endpoint as Collector (debug).
Run to get export in 2 batches (2 counters + 1 counter) of 1 ResourceMetrics each.

Does This PR Require a Contrib Repo Change?

Yes. - Link to PR:
No.

Checklist:

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

tammy-baylis-swi · 2025-05-09T19:08:48Z

I think the aiohttp-client test failure is a hiccup from the recent release, not from changes in this PR.

tammy-baylis-swi · 2025-05-09T19:20:46Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+        # used to write batched pb2 objects for export when finalized
+        split_resource_metrics = []
+
+        for resource_metrics in metrics_data.resource_metrics:


This borrows from the 4-deep for-each loop approach in the gRPC exporter.

tammy-baylis-swi · 2025-05-09T19:22:08Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+
+        for resource_metrics in metrics_data.resource_metrics:
+            split_scope_metrics = []
+            split_resource_metrics.append(


The split_* lists store references because the HTTP protobuf representations of ResourceMetrics, ScopeMetrics, etc are not replace-able like the gRPC data classes. I'm not sure if there's a better way -- doing CopyFrom and clear is still quite involved.

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

tammy-baylis-swi · 2025-05-09T19:24:39Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+                )
+            )
+
+    def _get_split_resource_metrics_pb2(


This helper is used to write actual pb2 objects before each yield back to the export caller.

lzchen · 2025-05-12T12:54:58Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+
+                    if split_resp.ok:
+                        export_result = MetricExportResult.SUCCESS
+                    elif self._retryable(split_resp):


Wouldn't we need to remove the success/failure batches from the entire list when we attempt a retry? For example, batch size of 1 and there are 2 metric datas. The first one returns retryable and the second one returns failure. When the loop returns to the outer loop, we don't want to retry the one that failed again right?

Good call, no we don't want to retry a non-retryable failure!

I reorganized the unbatched-vs-batched and, for the latter, made batch the outer loop and delay the inner loop with breaks for clarity in f1ef6c4.

Hi @lzchen any other changes to suggest?

tammy-baylis-swi · 2025-07-03T17:25:02Z

Working on some conflict resolution with changes introduced in #4564

tammy-baylis-swi · 2025-07-03T21:46:16Z

Hi @lzchen and @open-telemetry/python-approvers , please may I have a new review of this PR.

In 25e8be9 I resolved merge conflicts which required some redesign of HTTP metrics batching to match the timeout updates in #4564. That was the main change since last approval; the split helpers are the same.

The last Cassandra and Celery instrumentor test failures seem unrelated and are citing commit hashes like similar failures in other PRs.

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

pmcollins

Added a couple of comments. LGTM otherwise after checks pass.

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

tammy-baylis-swi · 2025-08-21T18:20:34Z

Hi @open-telemetry/python-approvers , any other revisions needed for this one?

tammy-baylis-swi · 2025-11-12T17:24:48Z

Hi again @open-telemetry/python-approvers , @open-telemetry/python-maintainers please could I have a review of this?

tammy-baylis-swi · 2026-01-15T23:47:04Z

Hi again @open-telemetry/python-approvers , @open-telemetry/python-maintainers please could I have a review of this?

Hi again, please may I have a review

42Questions

Two comments re implementation.

42Questions · 2026-02-12T17:54:50Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+        for split_metrics_data in split_metrics_batches:
+            export_result = self._export_with_retries(
+                split_metrics_data.SerializeToString(),
+                deadline_sec,
+            )


Is it ok for data loss to happen here?
For example if there are two batches and the first one fails, and the first one succeeds.
I can see that there is a test that confirms the behaviour test_export_retries_with_batching_failure_first, would just like to make sure that it's intentional.

It looks like the gRPC MetricExporter returns failure if any batch fails - we should probably be consistent between the exporters.

Thank you both. In 6f5efbf I've set it to fail fast instead.

42Questions · 2026-02-12T18:47:14Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

        return True


+def _split_metrics_data(


This seems quite verbose, are the if elif chains needed?
I think all metric types (sum, histogram, gauge, etc.) have a data_points field within their data container, could we use WhichOneof() and CopyFrom() to handle them agnostically?

Yes you're right! In c5ddba8 I cut out several elif using WhichOneof. CopyFrom didn't quite work but getattr does.

MikeGoldsmith

Looks good. Left one comment regarding reporting failures across batches.

MikeGoldsmith · 2026-02-16T13:23:00Z

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

+        for split_metrics_data in split_metrics_batches:
+            export_result = self._export_with_retries(
+                split_metrics_data.SerializeToString(),
+                deadline_sec,
+            )


It looks like the gRPC MetricExporter returns failure if any batch fails - we should probably be consistent between the exporters.

MikeGoldsmith

🚀

tammy-baylis-swi added 3 commits May 9, 2025 11:03

Add OTLP HTTP MetricExporter max export batch size

a62f2ee

Changelog

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Lint

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tammy-baylis-swi marked this pull request as ready for review May 9, 2025 19:07

tammy-baylis-swi requested a review from a team as a code owner May 9, 2025 19:07

tammy-baylis-swi added this to @xrmx's Python PR digest May 9, 2025

tammy-baylis-swi moved this to Ready for review in @xrmx's Python PR digest May 9, 2025

tammy-baylis-swi commented May 9, 2025

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tammy-baylis-swi commented May 9, 2025

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lzchen reviewed May 12, 2025

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tammy-baylis-swi and others added 2 commits May 12, 2025 15:01

HTTP metrics export batching does not retry if big failure

f1ef6c4

Merge branch 'main' into otlp-http-metrics-export-max-batch

60fd40f

tammy-baylis-swi requested a review from lzchen May 12, 2025 22:06

tammy-baylis-swi added 6 commits May 15, 2025 09:08

Merge branch 'main' into otlp-http-metrics-export-max-batch

ecd86f7

Merge branch 'main' into otlp-http-metrics-export-max-batch

f791c59

Merge branch 'main' into otlp-http-metrics-export-max-batch

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Merge branch 'main' into otlp-http-metrics-export-max-batch

3fb7f3a

Merge branch 'main' into otlp-http-metrics-export-max-batch

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Merge branch 'main' into otlp-http-metrics-export-max-batch

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lzchen approved these changes Jun 25, 2025

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tammy-baylis-swi added 2 commits July 3, 2025 14:26

Merge branch 'main' into otlp-http-metrics-export-max-batch

25e8be9

Fix changelog

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tammy-baylis-swi requested review from a team and lzchen July 3, 2025 21:46

pmcollins reviewed Jul 7, 2025

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tammy-baylis-swi added 2 commits July 14, 2025 17:27

Update http metric exporter batch return to be like grpc

fb6043b

Fix tests

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pmcollins approved these changes Jul 15, 2025

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...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py Outdated Show resolved Hide resolved

...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py Outdated Show resolved Hide resolved

Actually return last batch result like grpc

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tammy-baylis-swi commented Jul 15, 2025

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...orter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py Outdated Show resolved Hide resolved

Mv _split_metrics_data out of class

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tammy-baylis-swi requested review from a team and pmcollins July 15, 2025 23:19

Merge branch 'main' into otlp-http-metrics-export-max-batch

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tammy-baylis-swi removed the status in @xrmx's Python PR digest Aug 28, 2025

tammy-baylis-swi moved this to Ready for review in @xrmx's Python PR digest Aug 28, 2025

Merge branch 'main' into otlp-http-metrics-export-max-batch

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tammy-baylis-swi moved this from Ready for review to Easy to review / merge / close in @xrmx's Python PR digest Sep 2, 2025

tammy-baylis-swi added 2 commits September 9, 2025 10:13

Merge branch 'main' into otlp-http-metrics-export-max-batch

4b4efc9

Merge branch 'main' into otlp-http-metrics-export-max-batch

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tammy-baylis-swi added 2 commits November 20, 2025 09:22

Merge branch 'main' into otlp-http-metrics-export-max-batch

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Merge branch 'main' into otlp-http-metrics-export-max-batch

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tammy-baylis-swi moved this from Easy to review / merge / close to Ready for review in @xrmx's Python PR digest Jan 15, 2026

tammy-baylis-swi moved this from Ready for review to Easy to review / merge / close in @xrmx's Python PR digest Jan 15, 2026

42Questions reviewed Feb 12, 2026

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MikeGoldsmith reviewed Feb 16, 2026

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tammy-baylis-swi and others added 4 commits February 18, 2026 14:13

Merge branch 'main' into otlp-http-metrics-export-max-batch

301bbb3

Fix bad merge

8d3aff8

Simplify with WhichOneof, getattr

c5ddba8

HTTP MetricExporter fail fast for batches

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MikeGoldsmith approved these changes Feb 19, 2026

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Merge branch 'main' into otlp-http-metrics-export-max-batch

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