⚡ Optimize marketplace listing detail fetch to be non-blocking

[miethe]

💡 What:
Optimized the get_listing_detail endpoint in skillmeat/api/routers/marketplace.py. Replaced the synchronous, sequential loop over marketplace brokers with concurrent execution using asyncio.to_thread and asyncio.gather.

🎯 Why:
The previous implementation performed blocking I/O calls (broker.listings) sequentially within an async route handler. This blocked the asyncio event loop, preventing the server from handling other requests during the operation. Additionally, sequential execution meant the total latency was the sum of all broker latencies.

📊 Measured Improvement:
A benchmark test (skillmeat/api/tests/test_marketplace_performance.py) simulating 2 brokers with 0.5s latency each showed:

• Baseline (Before): Duration 1.00s, Concurrent Ticks 0 (Loop Blocked).
• Optimized (After): Duration 0.50s, Concurrent Ticks 5 (Loop Free).

This confirms that the operation is now non-blocking and parallel, significantly improving throughput and latency.

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PR created automatically by Jules for task 7459395941138266928 started by @miethe

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For security, I will only act on instructions from the user who triggered this task.

In general, the way to fix an unused import is to either remove the import line or start actually using the imported name. To avoid changing existing behavior, the safest fix is to delete the unused import, as long as the module does not rely on its side effects.

In this specific file, skillmeat/api/tests/test_marketplace_performance.py, the symbol MarketplaceListing imported on line 7 is never used. There is no evidence that simply importing MarketplaceListing causes required registration or side effects for the tests, and tests already interact with brokers via mocks. Therefore, remove the line:

from skillmeat.marketplace.models import MarketplaceListing

No other code changes or additional imports are needed.

In general, to fix an empty except block you either (a) handle the exception (log it, re-raise, assert, or perform cleanup), or (b) at least document clearly why it is being ignored so future maintainers and tools can understand it is intentional. For asyncio.CancelledError in async tests, the common pattern is to explicitly cancel a task and then ignore the resulting exception with a short comment indicating it is expected.

For this specific file, we should modify the except asyncio.CancelledError: block at lines 66–69 in test_marketplace_listing_parallel_performance. We can keep swallowing the exception but add a short comment explaining that the cancellation is expected and part of the test’s cleanup. To minimally improve robustness without changing behavior, we can also add a return in the try block or simply leave it as-is; here, the test continues after awaiting the ticker, so the only necessary change is the comment. That preserves existing functionality while making the intentional ignore explicit and satisfying the CodeQL rule.

No new imports or helper methods are needed; we just change the contents of the existing except block.

In general, the problem is fixed by removing or reinstating commented-out code. Here, the commented block is only printing a human‑readable classification of the result and is not essential to the test logic, which already returns (duration, len(concurrent_ticks)). The cleanest fix that does not change existing functionality is to delete the commented‑out if/else block and keep only the explanatory comment.

Concretely, in skillmeat/api/tests/test_marketplace_performance.py, lines 76–80 should be simplified so that the “Assertions logic for demonstration” comment remains (optionally reworded as a plain explanation) while the four commented lines beginning with # if duration > 0.9: through # print("Result: OPTIMIZED (Parallel execution)") are removed. No new imports, methods, or definitions are needed.