[EXPORTER] Add support for otlp exporter collection limits #3816

Joshua-Elsner · 2026-01-19T04:31:25Z

This PR implements collection limits (max attributes, max events, max links, etc.) directly in the OTLP Exporter options. This allows users to enforce limits at the exporter level, which is useful when the exporter is used in a "firehose" mode or independently of the SDK limits.

Changes

OtlpRecordable: Added logic to check limits in SetAttribute, AddEvent, and AddLink. Drops are tracked in the proto dropped_counts.
Options: Added 5 limit fields to OtlpHttpExporterOptions and OtlpGrpcExporterOptions (default: UINT32_MAX / no limit).
Exporters: Updated MakeRecordable in both HTTP and gRPC exporters to pass the configured limits to the recordable.
Tests: Added unit tests in otlp_recordable_test.cc to verify drops occur when limits are exceeded.
For significant contributions please make sure you have completed the following items:
CHANGELOG.md updated for non-trivial changes
I did not update CHANGELOG.md to avoid merge conflicts, but I am happy to add an entry if requested.
Unit tests have been added
Changes in public API reviewed

Signed-off-by: Joshua <[email protected]>

linux-foundation-easycla · 2026-01-19T04:31:32Z

The committers listed above are authorized under a signed CLA.

✅ login: Joshua-Elsner / name: Joshua (b38001d, c0d5c17)
✅ login: lalitb / name: Lalit Kumar Bhasin (144d389)

codecov · 2026-01-19T08:21:04Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.96%. Comparing base (2245926) to head (b38001d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3816      +/-   ##
==========================================
+ Coverage   89.94%   89.96%   +0.03%     
==========================================
  Files         225      225              
  Lines        7170     7170              
==========================================
+ Hits         6448     6450       +2     
+ Misses        722      720       -2

see 2 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

Signed-off-by: Joshua <[email protected]>

Copilot

Pull request overview

This PR implements collection limits for the OTLP exporter, allowing users to enforce constraints on attributes, events, and links at the exporter level. These limits are useful in "firehose" mode scenarios where the exporter operates independently of SDK limits. The implementation adds limit checks that increment dropped counters when thresholds are exceeded, providing proper telemetry signal loss tracking.

Changes:

Added five configurable limit parameters to both HTTP and gRPC OTLP exporter options with UINT32_MAX defaults (no limit)
Implemented limit enforcement in OtlpRecordable for attributes, events, links, and their nested attributes
Added comprehensive unit tests verifying limit enforcement and dropped count tracking

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
exporters/otlp/include/opentelemetry/exporters/otlp/otlp_recordable.h	Added constructor parameters and private members for collection limits
exporters/otlp/include/opentelemetry/exporters/otlp/otlp_http_exporter_options.h	Added five limit configuration fields to HTTP exporter options
exporters/otlp/include/opentelemetry/exporters/otlp/otlp_grpc_exporter_options.h	Added five limit configuration fields to gRPC exporter options
exporters/otlp/src/otlp_recordable.cc	Implemented limit checking logic in SetAttribute, AddEvent, and AddLink methods
exporters/otlp/src/otlp_http_exporter.cc	Updated MakeRecordable to pass configured limits from options
exporters/otlp/src/otlp_grpc_exporter.cc	Updated MakeRecordable to pass configured limits from options
exporters/otlp/test/otlp_recordable_test.cc	Added test case validating limit enforcement for attributes, events, and per-event attributes

Copilot · 2026-01-21T08:20:58Z

exporters/otlp/test/otlp_recordable_test.cc

+TEST(OtlpRecordableTest, TestCollectionLimits)
+{
+  // Initialize recordable with strict limits:
+  // Max Attributes: 2, Max Events: 2, Max Links: 2
+  // Max Attributes Per Event: 1, Max Attributes Per Link: 1
+  OtlpRecordable recordable(2, 2, 2, 1, 1);
+
+  // Test Attribute Limits
+  recordable.SetAttribute("attr1", 1);
+  recordable.SetAttribute("attr2", 2);
+  recordable.SetAttribute("attr3", 3);  // Should be dropped
+
+  EXPECT_EQ(recordable.span().attributes_size(), 2);
+  EXPECT_EQ(recordable.span().dropped_attributes_count(), 1);
+
+  // Test Event Limits
+  std::map<std::string, int> empty_map;
+  common::KeyValueIterableView<std::map<std::string, int>> empty_attrs(empty_map);
+
+  recordable.AddEvent("event1", std::chrono::system_clock::now(), empty_attrs);
+  recordable.AddEvent("event2", std::chrono::system_clock::now(), empty_attrs);
+  recordable.AddEvent("event3", std::chrono::system_clock::now(),
+                      empty_attrs);  // Should be dropped
+
+  EXPECT_EQ(recordable.span().events_size(), 2);
+  EXPECT_EQ(recordable.span().dropped_events_count(), 1);
+
+  // Test Per-Event Attribute Limits
+  std::map<std::string, int> attr_map = {{"e_attr1", 1}, {"e_attr2", 2}};
+  common::KeyValueIterableView<std::map<std::string, int>> event_attrs(attr_map);
+
+  OtlpRecordable event_recordable(10, 10, 10, 1, 1);
+  event_recordable.AddEvent("event_with_attrs", std::chrono::system_clock::now(), event_attrs);
+
+  auto &event_list = event_recordable.span().events();
+  ASSERT_EQ(event_list.size(), 1);
+  // The event itself should have 1 attribute, and 1 dropped
+  EXPECT_EQ(event_list[0].attributes_size(), 1);
+  EXPECT_EQ(event_list[0].dropped_attributes_count(), 1);
+}


The test case validates attribute limits, event limits, and per-event attribute limits, but it does not test the link limits (max_links) or per-link attribute limits (max_attributes_per_link). Add test coverage for these scenarios to ensure the AddLink method correctly enforces limits and tracks dropped links and dropped link attributes.

@Joshua-Elsner

At first glance, looks like cp is correct here, and the test can be expanded for more coverage.
Please check and add test cases as needed.

exporters/otlp/include/opentelemetry/exporters/otlp/otlp_grpc_exporter_options.h

Signed-off-by: Joshua <[email protected]>

…-Elsner/opentelemetry-cpp into feature/3303-otlp-exporter-limits

marcalff

Thanks for the contribution.

See a minor comment, looks good otherwise.

marcalff · 2026-01-28T14:35:48Z

exporters/otlp/include/opentelemetry/exporters/otlp/otlp_recordable.h

+  explicit OtlpRecordable(uint32_t max_attributes           = UINT32_MAX,
+                          uint32_t max_events               = UINT32_MAX,
+                          uint32_t max_links                = UINT32_MAX,
+                          uint32_t max_attributes_per_event = UINT32_MAX,
+                          uint32_t max_attributes_per_link  = UINT32_MAX)


For consistency, please use std::uint32_t and std::numeric_limits<std::uint32_t>::max() as well.

marcalff

Also, see comment on code coverage.

marcalff · 2026-01-28T14:45:05Z

exporters/otlp/test/otlp_recordable_test.cc

+TEST(OtlpRecordableTest, TestCollectionLimits)
+{
+  // Initialize recordable with strict limits:
+  // Max Attributes: 2, Max Events: 2, Max Links: 2
+  // Max Attributes Per Event: 1, Max Attributes Per Link: 1
+  OtlpRecordable recordable(2, 2, 2, 1, 1);
+
+  // Test Attribute Limits
+  recordable.SetAttribute("attr1", 1);
+  recordable.SetAttribute("attr2", 2);
+  recordable.SetAttribute("attr3", 3);  // Should be dropped
+
+  EXPECT_EQ(recordable.span().attributes_size(), 2);
+  EXPECT_EQ(recordable.span().dropped_attributes_count(), 1);
+
+  // Test Event Limits
+  std::map<std::string, int> empty_map;
+  common::KeyValueIterableView<std::map<std::string, int>> empty_attrs(empty_map);
+
+  recordable.AddEvent("event1", std::chrono::system_clock::now(), empty_attrs);
+  recordable.AddEvent("event2", std::chrono::system_clock::now(), empty_attrs);
+  recordable.AddEvent("event3", std::chrono::system_clock::now(),
+                      empty_attrs);  // Should be dropped
+
+  EXPECT_EQ(recordable.span().events_size(), 2);
+  EXPECT_EQ(recordable.span().dropped_events_count(), 1);
+
+  // Test Per-Event Attribute Limits
+  std::map<std::string, int> attr_map = {{"e_attr1", 1}, {"e_attr2", 2}};
+  common::KeyValueIterableView<std::map<std::string, int>> event_attrs(attr_map);
+
+  OtlpRecordable event_recordable(10, 10, 10, 1, 1);
+  event_recordable.AddEvent("event_with_attrs", std::chrono::system_clock::now(), event_attrs);
+
+  auto &event_list = event_recordable.span().events();
+  ASSERT_EQ(event_list.size(), 1);
+  // The event itself should have 1 attribute, and 1 dropped
+  EXPECT_EQ(event_list[0].attributes_size(), 1);
+  EXPECT_EQ(event_list[0].dropped_attributes_count(), 1);
+}


@Joshua-Elsner

At first glance, looks like cp is correct here, and the test can be expanded for more coverage.
Please check and add test cases as needed.

marcalff · 2026-01-28T14:47:56Z

I did not update CHANGELOG.md to avoid merge conflicts, but I am happy to add an entry if requested.

Please rebase the patch, fix remaining comments, and add a CHANGELOG entry.

Will merge after that.

Joshua-Elsner added 4 commits January 18, 2026 22:33

exporters/otlp: implement collection limits logic in OtlpRecordable

72adf6c

Signed-off-by: Joshua <[email protected]>

exporters/otlp: add limit options to OTLP exporter configuration

2e399b3

Signed-off-by: Joshua <[email protected]>

exporters/otlp: apply configured limits in OTLP exporters

0df2a86

Signed-off-by: Joshua <[email protected]>

exporters/otlp: add unit tests for collection limits

8177464

Signed-off-by: Joshua <[email protected]>

Joshua-Elsner requested a review from a team as a code owner January 19, 2026 04:31

Joshua-Elsner and others added 4 commits January 19, 2026 16:45

fix: resolve signed/unsigned comparison warnings in OtlpRecordable

84572ac

Signed-off-by: Joshua <[email protected]>

Merge branch 'main' into feature/3303-otlp-exporter-limits

e819ec2

Merge branch 'main' into feature/3303-otlp-exporter-limits

6a4c884

Merge branch 'main' into feature/3303-otlp-exporter-limits

c26ba7b

lalitb requested a review from Copilot January 21, 2026 08:18

Copilot started reviewing on behalf of lalitb January 21, 2026 08:18 View session

Copilot AI reviewed Jan 21, 2026

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owent approved these changes Jan 22, 2026

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marcalff and others added 4 commits January 22, 2026 14:27

Merge branch 'main' into feature/3303-otlp-exporter-limits

91c910c

Merge branch 'main' into feature/3303-otlp-exporter-limits

e22546a

Merge branch 'main' into feature/3303-otlp-exporter-limits

f949bcb

Merge branch 'main' into feature/3303-otlp-exporter-limits

144d389

ThomsonTan reviewed Jan 26, 2026

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exporters/otlp/include/opentelemetry/exporters/otlp/otlp_grpc_exporter_options.h Outdated Show resolved Hide resolved

Joshua-Elsner added 2 commits January 28, 2026 03:25

fix: use std::numeric_limits instead of macro

c0d5c17

Signed-off-by: Joshua <[email protected]>

Merge branch 'feature/3303-otlp-exporter-limits' of github.com:Joshua…

b38001d

…-Elsner/opentelemetry-cpp into feature/3303-otlp-exporter-limits

marcalff reviewed Jan 28, 2026

View reviewed changes

marcalff changed the title ~~Feature/3303 otlp exporter limits~~ [EXPORTER] Add support for otlp exporter collection limits Jan 28, 2026

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[EXPORTER] Add support for otlp exporter collection limits #3816

[EXPORTER] Add support for otlp exporter collection limits #3816

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