feat(python): expose OTLP log and metric APIs

[bbednarski9]

Overview

Expose the core OTLP log and metric contracts through the Python and PyO3 APIs.

This is stack PR 2 of 5.

Stack navigation

1. #780 — Core runtime, shared event model, config v4, and CLI
2. #781 — Python and PyO3 bindings — this PR
3. #782 — Node.js and N-API bindings
4. #783 — C FFI and Go bindings
5. #779 — Dynamic native/gRPC plugins and consolidated docs

Position: 2 of 5 · GitHub base: main · Logical predecessor: #780 · Layer-only diff: compare branches · Next: #782

All five PRs target main. Their branches are cumulative: this PR includes every preceding layer until those PRs merge and this branch is rebased onto the updated main. The GitHub Files changed tab therefore shows the cumulative diff. Use the layer-only comparison above to review only the code introduced by this layer.

Review and merge in order: #780 → #781 → #782 → #783 → #779. After each merge, rebase the next branch onto the updated main; its PR remains targeted at main and its cumulative diff contracts to the remaining layers.

• I confirm this contribution is my own work, or I have the right to submit it under this project's license.
• I searched existing issues and open pull requests, and this does not duplicate existing work.

Details

• Add Python severity, metric measurement, metric kind, and metric value-type surfaces.
• Add optional data_schema and severity arguments to mark and pending-mark APIs.
• Add metric() and direct OpenTelemetryLogSubscriber and OpenTelemetryMetricSubscriber lifecycle APIs.
• Add version 4 observability log and metric configuration helpers.
• Update exports, stubs, package guidance, and Python parity tests.

Validation:

• cargo check -p nemo-relay-python --all-targets
• Ruff lint and formatting checks passed.
• Focused Python binding suite: 163 passed.
• Full Python suite on the complete stack: 660 passed.

Breaking changes: none.

Where should the reviewer start?

Start with crates/python/src/py_types/observability.rs for native subscriber bindings and python/nemo_relay/scope.py for the public mark and metric helpers.

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• Relates to: feat(observability): add core OTLP log and metric pipelines #780

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[github-actions]

Fern docs preview: https://nvidia-preview-pull-request-781.docs.buildwithfern.com/nemo/relay/dev

[github-actions]

License Diff

Compared against origin/main.

Lockfile license changes

Lockfile License Changes

Rust

Added

• None

Removed

• None

Updated/Changed

• None

Node

Added

• None

Removed

• None

Updated/Changed

• None

Python

Added

• None

Removed

• None

Updated/Changed

• None

Status output

[license-diff] selected languages: rust, node, python
[license-diff] generating current inventory
[license-diff] current: generating Rust inventory
[license-diff] current: Rust inventory complete (448 packages)
[license-diff] current: generating Node inventory
[license-diff] current: Node inventory complete (367 packages)
[license-diff] current: generating Python inventory
[license-diff] current: Python inventory complete (105 packages)
[license-diff] current inventory complete
[license-diff] checking out base ref origin/main into a temporary worktree
[license-diff] base: generating Rust inventory
[license-diff] base: Rust inventory complete (448 packages)
[license-diff] base: generating Node inventory
[license-diff] base: Node inventory complete (367 packages)
[license-diff] base: generating Python inventory
[license-diff] base: Python inventory complete (105 packages)
[license-diff] base inventory complete
[license-diff] removing temporary base worktree
[license-diff] comparing inventories
[license-diff] rendering Markdown output
[license-diff] done

[bbednarski9]

Stack handoff from #780: this PR owns the Python pending-mark parity for data_schema and severity. I verified the current branch adds both constructor arguments, getters, and PendingMarkSpec conversion. Please double-check the accompanying tests preserve both fields through middleware pending-mark emission before merge.

[bbednarski9]

Follow-up for Observability V4: please update Python's typed helper surface with the new logs and metrics sections and make helper-created configs default to version: 4.\n\nToday ObservabilityConfig still emits v3, while core rejects v3 configs that contain logs or metrics. Please add regression coverage for creating a V4 logs/metrics config through the typed helpers.