feat(observability): add instance info to trace root span

[bzp2010]

Summary by CodeRabbit

• Refactor

  • Streamlined initialization sequence and observability configuration setup
  • Instance tracking identifiers now included in distributed traces for enhanced observability and debugging

• Bug Fixes

  • Enhanced error messages for initialization failures with additional context information

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR relocates instance initialization from the library's startup routine to the main program entry point and enhances observability by centralizing resource creation and adding instance identifiers to distributed traces.

Changes

Instance Initialization and Observability Refactor

Layer / File(s)	Summary
Observability Resource Centralization src/utils/observability/mod.rs	A new private get_resource() helper centralizes OpenTelemetry Resource construction with service name. Both trace and metric initialization now call this helper instead of inline construction.
Startup Flow Relocation src/lib.rs, src/main.rs	instance::init() is removed from lib.rs::run() and moved to main.rs with added error context via anyhow::Context. The import in lib.rs is updated to import only init_observability.
Trace Instrumentation src/proxy/middlewares/trace.rs	Root span initialization now includes instance-identifying properties (aisix.instance_id and aisix.instance_run_id) fetched from the instance module, supported by a new local attributes module defining span property key constants.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• feat(observability): pluggable span exporter #64: Moved/added init_observability into utils::observability and made utils public, directly supporting the import change in this PR's lib.rs.
• feat: fastrace tokio-based reporter #79: Modifies observability initialization in src/utils/observability/mod.rs (async reporter with tokio runtime), overlaps with Resource construction refactoring.
• feat: add instance id and run id #67: Modifies program startup to relocate or remove utils::instance::init(), directly related to the instance initialization relocation in main.rs and lib.rs.

🚥 Pre-merge checks | ✅ 5 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
E2e Test Quality Review	⚠️ Warning	PR lacks E2E test coverage for observability feature and introduces safety regression: trace middleware calls functions that panic if instance::init() isn't called, but initialization was moved to binary entrypoint only, breaking library embedders.	Add E2E tests for trace spans with instance IDs and ensure library safety by calling instance::init() from library entrypoint or making instance_id()/run_id() return Option with fallbacks.

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately describes the main change: adding instance info to trace root span properties.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Security Check	✅ Passed	Pull request adds non-sensitive telemetry identifiers (instance_id, run_id) to OpenTelemetry trace spans and refactors observability code without exposing credentials, secrets, or sensitive data.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bzp/feat-o11y-trace-instance-info

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/main.rs`:
- Line 9: The library must guarantee instance::init() is called for non-CLI
embedders; update the library entry points (run(), run_with_config(),
run_with_provider() in src/lib.rs) to call aisix::utils::instance::init() (or a
fallible variant) during startup before any request handling, or alternatively
make instance_id()/run_id() return Option/Result instead of panicking when the
OnceLock is uninitialized; ensure the chosen fix references and initializes the
OnceLock used by instance::init() (or changes the getters) so trace middleware
(src/proxy/middlewares/trace.rs) no longer panics for embedder usage.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 2ba06659-12b2-4c28-9b6e-a3b83bbef080

📥 Commits

Reviewing files that changed from the base of the PR and between 77bd85e and db4c9d3.

📒 Files selected for processing (4)

• src/lib.rs
• src/main.rs
• src/proxy/middlewares/trace.rs
• src/utils/observability/mod.rs