[OTLP] Add support for GZip compression by martincostello · Pull Request #7055 · open-telemetry/opentelemetry-dotnet

martincostello · 2026-04-10T13:07:57Z

Fixes #3961

Changes

Add support for GZip compression to the OTLP exporter.

Continues the work started in #6494.

Once released, should also update the compliance matrix.

Merge requirement checklist

CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
Unit tests added/updated
Appropriate CHANGELOG.md files updated for non-trivial changes
Changes in public API reviewed (if applicable)

codecov · 2026-04-10T13:16:24Z

Codecov Report

❌ Patch coverage is 98.18182% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.51%. Comparing base (805a2a8) to head (04349f2).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
.../Implementation/ExportClient/PooledBufferStream.cs	97.27%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7055      +/-   ##
==========================================
+ Coverage   89.26%   89.51%   +0.25%     
==========================================
  Files         271      272       +1     
  Lines       13088    13296     +208     
==========================================
+ Hits        11683    11902     +219     
+ Misses       1405     1394      -11

Flag	Coverage Δ
unittests-Project-Experimental	`89.39% <98.18%> (+0.20%)`	⬆️
unittests-Project-Stable	`89.39% <98.18%> (+0.22%)`	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ol/Implementation/ExportClient/OtlpExportClient.cs	`100.00% <100.00%> (ø)`
...mplementation/ExportClient/OtlpGrpcExportClient.cs	`79.31% <100.00%> (+4.57%)`	⬆️
...mplementation/ExportClient/OtlpHttpExportClient.cs	`100.00% <100.00%> (ø)`
...tation/OpenTelemetryProtocolExporterEventSource.cs	`57.50% <100.00%> (+1.08%)`	⬆️
...orter.OpenTelemetryProtocol/OtlpExporterOptions.cs	`99.37% <100.00%> (+0.09%)`	⬆️
.../Implementation/ExportClient/PooledBufferStream.cs	`97.27% <97.27%> (ø)`

... and 8 files with indirect coverage changes

Copilot

Pull request overview

Adds configurable gzip compression support to the OTLP exporter to align with the OTLP exporter specification (including env var configuration) and validates behavior via new/updated unit tests.

Changes:

Introduces OtlpExportCompression and OtlpExporterOptions.Compression, with spec env var support (OTEL_EXPORTER_OTLP*_COMPRESSION).
Implements gzip request compression for OTLP over HTTP and gRPC export clients.
Adds/updates unit tests and updates changelog + public API tracking files.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpSpecConfigDefinitionTests.cs	Extends spec config test data and assertions to include compression env vars.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpHttpExportClientTests.cs	Adds HTTP export tests validating payload and headers with/without gzip.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpGrpcExportClientTests.cs	Adds gRPC export tests validating compressed framing and decompression behavior.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs	Extends options/config tests to cover compression env var parsing and invalid values.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs	Adds `Compression` option, parsing helper, and spec-env-var application.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExportCompression.cs	New public enum defining supported compression modes.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/IOtlpExporterOptions.cs	Adds `Compression` to internal options contract.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/OtlpSpecConfigDefinitions.cs	Adds spec env var constants for compression across signals.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpHttpExportClient.cs	Implements gzip compression for HTTP request content.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs	Implements gzip compression for gRPC framing + request header.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpExportClient.cs	Centralizes content creation via overridable method; wires `CompressionEnabled`.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md	Documents new opt-in gzip compression configuration.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/.publicApi/Stable/PublicAPI.Unshipped.txt	Tracks new public API surface (`OtlpExportCompression`, `OtlpExporterOptions.Compression`).

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Add support for GZip compression to the OTLP exporter. Picks up from open-telemetry#6494. Resolves open-telemetry#3961. Co-Authored-By: Hannah Haering <157852144+hannahhaering@users.noreply.github.com>

- Avoid allocating a buffer for every write of compressed gRPC data. - Simplify `IsTransientNetworkError()`.

Add coverage for different ways to specify the compression value.

- Ensure only one `grpc-encoding` header. - Remove redundant null checks.

Remove trailing spaces.

Add missing blank line.

cijothomas · 2026-04-26T20:14:06Z


+* Added opt-in support for gzip compression. Compression can be configured
+  programmatically via the new `OtlpExporterOptions.Compression` property,
+  or through the environment variables such as `OTEL_EXPORTER_OTLP_COMPRESSION=gzip`.


nit: maybe mention the signal specific env vars too here.

also, if we can update the OTLP's readme also, that'd better.

Good point - I forgot about the README.

README updated.

cijothomas · 2026-04-26T20:18:41Z

+            return base.CreateHttpContent(buffer, contentLength);
+        }
+
+        var compressedStream = new MemoryStream();


lets leave a todo for a future optimization to see if we can avoid allocation by renting/pooling arrays.

What specifically were you thinking of?

Renting a buffer to pass into the MemoryStream?

Renting a single shared buffer (like the main exporter does) for compression and re-using it across requests to pass into the MemoryStream?

A custom Stream implementation that acts like a memory stream but is backed by rented buffers?

Something else?

I've got an implementation of the third option locally, I'm just testing it.

https://github.com/communityToolkit/dotnet has quite a few implementations.

We wouldn't be able to take a dependency on those.

I wouldn't recommend that for this library either.

But it has quite a few with unit tests.

I don't see a problem grabbing the code from one that fits here.

I took a quick look, and didn't see an "obvious" one that grabbed from the array pool, plus they seemed to have a bunch of extra interfaces I'd have to prune out. As I'd already written an implementation when you commented, I'll stick with that unless there's a compelling reason to replace it with something adapted and vendored from there.

Oops! I meant to leave a TODO for revisiting this in a future PR to keep the initial version easier to review. My suggestion is to avoid the optimization in this PR, so review can focus on just the feature, and then a follow up where we can focus on pooling/efficiency part!

Sorry I was not very clear initially!

As I've already done the work either I can remove it and just immediately open a PR as a draft that's the same plus 2 extra files to rebase later and then re-run the benchmarks without the optimization, or we can just leave it in.

Log the compressed and uncompressed sizes when using GZip.

Add an implementation of `Stream` that uses pooled buffers.

Rename to `GZip` to match `GZipStream`.

Add documentation for compression.

Add a benchmark for OTLP compression.

martincostello · 2026-04-27T14:00:05Z

Benchmark results


BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8246/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.203
  [Host]               : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
  .NET 10.0            : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
  .NET Framework 4.6.2 : .NET Framework 4.8.1 (4.8.9325.0), X64 RyuJIT VectorSize=256

Method	Job	Runtime	Compression	Mean	Error	StdDev	Median	Ratio	RatioSD	Allocated	Alloc Ratio
OtlpExporter_Compression	.NET 10.0	.NET 10.0	None	7.260 ms	0.1886 ms	0.5531 ms	7.075 ms	1.01	0.10	3.44 KB	1.00
OtlpExporter_Compression	.NET Framework 4.6.2	.NET Framework 4.6.2	None	18.818 ms	0.3736 ms	0.6444 ms	18.802 ms	2.61	0.21	6 KB	1.75

OtlpExporter_Compression	.NET 10.0	.NET 10.0	GZip	8.259 ms	0.1643 ms	0.2920 ms	8.248 ms	1.00	0.05	4.08 KB	1.00
OtlpExporter_Compression	.NET Framework 4.6.2	.NET Framework 4.6.2	GZip	40.743 ms	0.7962 ms	1.0070 ms	40.911 ms	4.94	0.21	136.59 KB	33.49

Stub-out the `HttpClient` requests.

Use a top-level program for benchmarks and return whether they have succeeded to the caller.

`Stream.CanTimeout` is already `false`.

Add coverage for `PooledBufferStream` that isn't already covered by other tests.

Rename `buf` to `rented` and fix trying to return an empty buffer.

Log the compression type in the event source.

Update PR number.

github-actions Bot added the pkg:OpenTelemetry.Exporter.OpenTelemetryProtocol Issues related to OpenTelemetry.Exporter.OpenTelemetryProtocol NuGet package label Apr 10, 2026

martincostello commented Apr 10, 2026

View reviewed changes

Comment thread ...Telemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs Outdated

martincostello marked this pull request as ready for review April 10, 2026 14:34

martincostello requested a review from a team as a code owner April 10, 2026 14:34

Copilot AI review requested due to automatic review settings April 10, 2026 14:34

Copilot started reviewing on behalf of martincostello April 10, 2026 14:34 View session

Copilot AI reviewed Apr 10, 2026

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martincostello mentioned this pull request Apr 12, 2026

[DNM] Performance improvements #7062

Closed

4 tasks

martincostello and others added 4 commits April 13, 2026 15:26

[OTLP] Add support for GZip compression

f617492

Add support for GZip compression to the OTLP exporter. Picks up from open-telemetry#6494. Resolves open-telemetry#3961. Co-Authored-By: Hannah Haering <157852144+hannahhaering@users.noreply.github.com>

[OTLP] Avoid allocating array

dbbfb44

- Avoid allocating a buffer for every write of compressed gRPC data. - Simplify `IsTransientNetworkError()`.

[OTLP] Extend test coverage

c18093b

Add coverage for different ways to specify the compression value.

[OTLP] Address feedback

3109a87

- Ensure only one `grpc-encoding` header. - Remove redundant null checks.

martincostello force-pushed the gh-3961 branch from 13137f9 to 3109a87 Compare April 13, 2026 14:26

martincostello added 2 commits April 14, 2026 18:04

Merge branch 'main' into open-telemetrygh-3961

3458338

Merge branch 'main' into open-telemetrygh-3961

59d7967

martincostello commented Apr 21, 2026

View reviewed changes

Comment thread ...Telemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs Outdated

[OLTP] Fix lint warning

09a0c68

Remove trailing spaces.

martincostello commented Apr 21, 2026

View reviewed changes

Comment thread ...Telemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs

[OLTP] Fix spacing

3b9d5c8

Add missing blank line.

cijothomas reviewed Apr 26, 2026

View reviewed changes

Comment thread ...Telemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpHttpExportClient.cs

martincostello added 5 commits April 27, 2026 13:17

[OTLP] Add verbose logs for compression

848ab7a

Log the compressed and uncompressed sizes when using GZip.

[OTLP] Add pooled memory stream

d2c4f77

Add an implementation of `Stream` that uses pooled buffers.

[OTLP] Rename enum member

870c70a

Rename to `GZip` to match `GZipStream`.

[OTLP] Update README

905e4ca

Add documentation for compression.

[OTLP] Add benchmark for compression

048b1ac

Add a benchmark for OTLP compression.

github-actions Bot added the perf Performance related label Apr 27, 2026

martincostello added 5 commits April 27, 2026 15:28

[OTLP] Fix compression benchmarks

93dd8df

Stub-out the `HttpClient` requests.

[Infra] Use top-level program

9f8b3f5

Use a top-level program for benchmarks and return whether they have succeeded to the caller.

[OTLP] Remove redundant override

43107f9

`Stream.CanTimeout` is already `false`.

[OTLP] Extend test coverage

c07c97a

Add coverage for `PooledBufferStream` that isn't already covered by other tests.

[OTLP] Rename variable

4dbc8c3

Rename `buf` to `rented` and fix trying to return an empty buffer.

cijothomas reviewed Apr 27, 2026

View reviewed changes

Comment thread ...ry.Exporter.OpenTelemetryProtocol/Implementation/OpenTelemetryProtocolExporterEventSource.cs

[OTLP] Log compression type

a0d9f15

Log the compression type in the event source.

rajkumar-rangaraj approved these changes Apr 27, 2026

View reviewed changes

Merge branch 'main' into open-telemetrygh-3961

64dbf61

martincostello commented Apr 28, 2026

View reviewed changes

Comment thread src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md Outdated

[OTLP] Fix CHANGELOG

04349f2

Update PR number.

martincostello enabled auto-merge April 28, 2026 09:12

martincostello added this pull request to the merge queue Apr 28, 2026

ysolomchenko mentioned this pull request Apr 28, 2026

Update OTel SDK/API to 1.16.0 open-telemetry/opentelemetry-dotnet-instrumentation#4941

Open

Merged via the queue into open-telemetry:main with commit 6232fb2 Apr 28, 2026
60 checks passed

martincostello deleted the gh-3961 branch April 28, 2026 10:00

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