HAL9000
d54ed1440c
Add MEMORY_ENGINES_LOCK to engine_cache.py and wrap the check-and-set in UnitOfWork.engine with it to prevent concurrent threads from creating duplicate in-memory SQLite engines. Also fix cache-hit bug where self._engine was never assigned on a cache hit. Closes #7566
36 lines
1.6 KiB
Gherkin
36 lines
1.6 KiB
Gherkin
Feature: Thread-safe engine cache prevents TOCTOU race on MEMORY_ENGINES
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As a developer relying on the in-memory SQLite engine cache
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I want MEMORY_ENGINES access to be protected by a lock
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So that concurrent threads cannot create duplicate engine instances for the same URL
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# --- Lock Export ---
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Scenario: MEMORY_ENGINES_LOCK is exported from engine_cache module
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Given the engine cache module is imported
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Then MEMORY_ENGINES_LOCK should be accessible from the engine_cache module
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And MEMORY_ENGINES_LOCK should be a threading.Lock instance
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# --- Cache-Hit Regression ---
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Scenario: A second UnitOfWork for the same in-memory URL reuses the cached engine
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Given the engine cache is cleared
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And a UnitOfWork is created for "sqlite:///:memory:"
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When a second UnitOfWork is created for "sqlite:///:memory:"
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Then both UnitOfWork instances should share the same engine instance
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# --- Lock Acquisition ---
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Scenario: The engine property acquires MEMORY_ENGINES_LOCK before creating an engine
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Given the engine cache is cleared
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And MEMORY_ENGINES_LOCK acquisition is tracked
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When a UnitOfWork engine is accessed for "sqlite:///:memory:"
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Then MEMORY_ENGINES_LOCK should have been acquired at least once
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# --- Concurrent Access ---
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Scenario: Concurrent engine creation for the same URL yields one engine instance
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Given the engine cache is cleared
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When 10 threads each access the engine cache for "sqlite:///:memory:"
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Then all threads should have received the same engine instance
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And MEMORY_ENGINES should contain exactly one entry for "sqlite:///:memory:"
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