LCORE-536 Add error handling for bad llama-stack URLs; no more silent fails

[max-svistunov]

Description

Adding proper error handling for incorrect llama-stack URL configurations that previously failed silently at startup. Malformed URLs and URLs with wrong scheme are now rejected; unreachable hosts result into error message.

Type of change

• Refactor
• New feature
• Bug fix
• CVE fix
• Optimization
• Documentation Update
• Configuration Update
• Bump-up service version
• Bump-up dependent library
• Bump-up library or tool used for development (does not change the final image)
• CI configuration change
• Konflux configuration change
• Unit tests improvement
• Integration tests improvement
• End to end tests improvement
• Benchmarks improvement

Tools used to create PR

Identify any AI code assistants used in this PR (for transparency and review context)

• Assisted-by: Claude Opus 4.5
• Generated by: Claude Opus 4.5

Related Tickets & Documents

• Related Issue # LCORE-536
• Closes # LCORE-536

Checklist before requesting a review

• I have performed a self-review of my code.
• PR has passed all pre-merge test jobs.
• If it is a core feature, I have added thorough tests.

Testing

1. In lightspeed-stack.yaml, set:

llama_stack:
url: not-a-valid-url

2. Startup should fail:

llama_stack.url
Input should be a valid URL, relative URL without a base

3. Same for invalid scheme (e.g. ftp://localhost:8321) and unreachable host (e.g. http://invalid-nonexistent-host:8321).

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Enhanced error handling and logging when Llama Stack service connection fails, providing clearer diagnostics

• Improvements

  • Stricter URL validation for Llama Stack configuration requiring valid HTTP(S) URLs to prevent misconfiguration

[max-svistunov]

@radofuchs Could you PTAL?

[coderabbitai]

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Walkthrough

The PR introduces stricter URL validation for Llama Stack configuration by changing the url field type from Optional[str] to Optional[AnyHttpUrl], adds error handling for API connection failures during startup, and updates the client to properly stringify URLs before initialization.

Changes

Cohort / File(s)	Summary
Configuration & Type Validation src/models/config.py	LlamaStackConfiguration.url field type changed from Optional[str] to Optional[AnyHttpUrl], enforcing URL format validation at the model level with updated field description.
Client Initialization src/client.py	Modified _load_service_client to stringify AnyHttpUrl values via str(config.url) before passing to client initialization, ensuring compatibility with HTTP client libraries.
Startup Error Handling src/app/main.py	Added APIConnectionError import and wrapped Llama Stack version check in try/except, logging connection failures with service URL and original exception details before re-raising.
Test Updates - Validation tests/unit/models/config/test_llama_stack_configuration.py	Added comprehensive test suite validating URL acceptance (http/https with trailing slash normalization), rejection of malformed URLs, and rejection of disallowed URL schemes.
Test Updates - Configuration tests/unit/models/config/test_authentication_configuration.py, tests/unit/test_configuration.py	Updated test data from bare "localhost" to fully-qualified "http://localhost" URLs; adjusted URL assertion to compare string representation with trailing slash normalization.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• LCORE-391: Refactoring: proper Llama Stack config name #261: Renames/normalizes LlamaStackConfiguration identifier while this PR modifies the same class's url field and client loading behavior.
• LCORE-381: new unit tests for client.py and models endpoints #287: Also adds handling of llama_stack_client.APIConnectionError and modifies client-holder behavior for Llama Stack interactions.

Suggested reviewers

• radofuchs
• tisnik

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[tisnik]

LGTM