Enforce OTLP request size limits

[ADITYA-CODE-SOURCE]

Fixes #8444.

Why

• opentelemetry-proto#782 now recommends that OTLP exporters enforce configurable outbound request/message size limits.
• OpenTelemetry Java already limits response body reads, but OTLP exporters did not enforce outbound request/message limits.

What

• add configurable request/message size limits to OTLP HTTP and gRPC exporter builders with a default of 64 MiB
• enforce the limit in the shared OTLP HTTP and gRPC exporter layers before dispatching requests
• cover both known-size binary payloads and unknown-size payloads (for example OTLP HTTP JSON) by measuring when needed
• add focused tests for over-limit failure behavior and builder configuration plumbing
• update docs/apidiffs/current_vs_latest/opentelemetry-exporter-otlp.txt for the new public builder methods

Testing

I was not able to complete local Gradle verification on this Windows machine because Gradle / the Kotlin compiler daemon repeatedly failed to start due to paging-file / metaspace limits before compilation finished. The changes are pushed for CI verification.

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-exporter-otlp

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[ADITYA-CODE-SOURCE]

@jkwatson Thanks — I pushed a follow-up that fixes the NullAway compile failure in the OTLP internal exporters and applies the naming nits to use constants and public API parameter names.

[jack-berg]

A few small comments, but looks pretty good! Thanks for working on this!

[ADITYA-CODE-SOURCE]

Fixed the remaining Spotless failure in OtlpGrpcProfilesExporterBuilder and pushed it in 17cec6745. The previous build failures were all caused by that formatting issue; rerunning CI now.

[jack-berg]

Looks like there are still some build failures from static analysis.

Couple more nits to fix along with the build, but looks good to me

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ADITYA-CODE-SOURCE / name: ADITYA-CODE-SOURCE (172e011, 26713e1, 301fe84, 3a22f35, 536ffe5, d3fc987, d47e13a, d69235b)

[ADITYA-CODE-SOURCE]

Rebased this branch onto current main and force-pushed the update.

Follow-up fixes in the latest push:

• moved the unknown-length measurement path into HttpExporter, which is where MessageWriter.getContentLength() < 0 actually matters
• simplified GrpcExporter to use Marshaler.getBinarySerializedSize() for the pre-send limit check
• switched the pre-send over-limit failure path to CompletableResultCode.ofExceptionalFailure(...)
• collapsed the testing-internal shared builder abstraction to a single transport-neutral setMaxRequestSize(...) method
• added coverage for the unknown-length HTTP over-limit case
• regenerated the OTLP API diff on top of current main (now 1.65.0-SNAPSHOT vs 1.64.0)

Local verification completed with:

• ./gradlew :exporters:otlp:all:test --tests "*HttpExporterTest" --tests "*GrpcExporterTest"
• ./gradlew :exporters:otlp:all:test :exporters:otlp:profiles:test
• ./gradlew :exporters:otlp:all:spotlessCheck :exporters:otlp:testing-internal:spotlessCheck :exporters:otlp:profiles:spotlessCheck
• ./gradlew :exporters:otlp:all:jApiCmp

[opentelemetry-pr-dashboard]

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[codecov]

Codecov Report

❌ Patch coverage is 89.04110% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.61%. Comparing base (8105b53) to head (a63c945).

Files with missing lines	Patch %	Lines
...telemetry/exporter/otlp/internal/HttpExporter.java	73.33%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8446      +/-   ##
============================================
- Coverage     91.61%   91.61%   -0.01%     
- Complexity    10316    10339      +23     
============================================
  Files          1013     1013              
  Lines         27278    27347      +69     
  Branches       3203     3206       +3     
============================================
+ Hits          24991    25053      +62     
- Misses         1560     1568       +8     
+ Partials        727      726       -1     

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[jack-berg]

@open-telemetry/java-approvers - heads up - this PR adds a default OTLP message / request body size of 64mb, where none currently exists. You could make the argument that this is a breaking behavior change, and that we should proceed but only once there is a env var / declarative config property to configure a different limit. (Ive opened open-telemetry/opentelemetry-configuration#695 to add declarative config schema to configure this)

Personally, I think the lack of current limit is a bug and adding a default of 64mb is a generous limit few will hit.