feat: support backoff/retry in OTLP

[scottgerring]

Fixes #3081, building on the work started by @AaronRM 🤝

Changes

A new retry module added to opentelemetry-sdk

Models the sorts of retry an operation may request (retry / can't retry / throttle), and provides a helper retry_with_backoff mechanism that can be used to wrap up a retryable operation and retry it. The helper relies on experimental_async_runtime for its runtime abstraction, to provide the actual pausing. It also takes a lambda to classify the error, so the caller can inform the retry mechanism if a retry is required.

A new retry_classification module added to opentelemetry-otlp

This bit takes the actual error responses that we get back over OTLP and maps them back to the retry model. Because this is OTLP-specific stuff it belongs here rather than alongside the retry code.

Retry binding

... happens in each one of the concrete exporters to tie it all together.

Also ...

• Extended exporter builders to allow the user to customise default retry policy
• Added new feature flags experimental-http-retry and experimental-grpc-retry which pull in the experimental-async-runtime dep and set everything up. This way we can get going with this now without having to stabilise the experimental-async-runtime feature.

Open Questions

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 74.12077% with 780 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.8%. Comparing base (ad88615) to head (9ba3a06).
⚠️ Report is 222 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-otlp/src/exporter/http/mod.rs	67.0%	162 Missing ⚠️
opentelemetry-sdk/src/metrics/data/mod.rs	13.4%	154 Missing ⚠️
opentelemetry-proto/src/transform/metrics.rs	11.1%	64 Missing ⚠️
...-sdk/src/metrics/internal/exponential_histogram.rs	65.1%	52 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/metrics.rs	0.0%	50 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/trace.rs	0.0%	48 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/logs.rs	0.0%	46 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/mod.rs	73.4%	42 Missing ⚠️
opentelemetry-sdk/src/metrics/instrument.rs	88.9%	29 Missing ⚠️
opentelemetry-sdk/src/logs/logger_provider.rs	92.0%	12 Missing ⚠️
... and 28 more

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3126     +/-   ##
=======================================
+ Coverage   79.6%   80.8%   +1.2%     
=======================================
  Files        124     128      +4     
  Lines      23174   23090     -84     
=======================================
+ Hits       18456   18676    +220     
+ Misses      4718    4414    -304     

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[Copilot]

Pull Request Overview

This PR implements retry logic with exponential backoff and jitter for OTLP exporters to handle transient failures gracefully, addressing issue #3081. The implementation supports both HTTP and gRPC protocols with protocol-specific error classification and server-provided throttling hints.

• Adds a new retry module to opentelemetry-sdk with configurable retry policies and exponential backoff
• Implements protocol-specific error classification in opentelemetry-otlp for HTTP and gRPC responses
• Integrates retry functionality into all OTLP exporters (traces, metrics, logs) for both HTTP and gRPC transports

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
opentelemetry-sdk/src/retry.rs	Core retry module with exponential backoff, jitter, and error classification
opentelemetry-otlp/src/retry_classification.rs	Protocol-specific error classification for HTTP and gRPC responses
opentelemetry-otlp/src/exporter/tonic/*.rs	gRPC exporter integration with retry functionality
opentelemetry-otlp/src/exporter/http/*.rs	HTTP exporter integration with retry functionality
opentelemetry-otlp/Cargo.toml	Feature flags and dependencies for retry support

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[bantonsson]

I think the HTTP exporters look good now. Love all those red lines.

[bantonsson]

👍🏼 for the HTTP code. I can't see a clear way to reuse more of the Tonic code.

[lalitb]

Sorry for delay. I would like to review during this week - assigning to myself.