Make DeclarativeRecipe.accumulator thread-safe with ThreadLocal#6810
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Make DeclarativeRecipe.accumulator thread-safe with ThreadLocal#6810
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DeclarativeRecipe.accumulator was a plain field that gets set during the scan phase via getInitialValue(). When the same DeclarativeRecipe instance is shared across concurrent recipe runs (e.g. via a recipe cache), one run's scan phase overwrites the accumulator set by another run. This causes the second run to use stale or null accumulator state during the edit phase, resulting in precondition scanning recipes producing incorrect results (typically 0 file changes). This changes the accumulator field to a ThreadLocal so each run thread gets its own independent accumulator. The clone() method is also overridden to create a fresh ThreadLocal for cloned instances.
zieka
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* Make DeclarativeRecipe.accumulator thread-safe with ThreadLocal DeclarativeRecipe.accumulator was a plain field that gets set during the scan phase via getInitialValue(). When the same DeclarativeRecipe instance is shared across concurrent recipe runs (e.g. via a recipe cache), one run's scan phase overwrites the accumulator set by another run. This causes the second run to use stale or null accumulator state during the edit phase, resulting in precondition scanning recipes producing incorrect results (typically 0 file changes). This changes the accumulator field to a ThreadLocal so each run thread gets its own independent accumulator. The clone() method is also overridden to create a fresh ThreadLocal for cloned instances. * Clean up ThreadLocal in onComplete() to prevent memory leaks
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…veRecipe PR openrewrite#6810 changed DeclarativeRecipe.accumulator from a plain field to ThreadLocal to fix concurrent recipe runs overwriting each other's accumulator. However, ThreadLocal values are lost when execution resumes on a different thread after yielding. The accumulator is already stored on the rootCursor by ScanningRecipe.getAccumulator(), which is per-run and survives thread switches. This change removes the redundant ThreadLocal storage and instead resolves the accumulator from the rootCursor at visit time. The PreconditionBellwether now defers precondition resolution to visit time (when the rootCursor is available) rather than eagerly resolving in a field initializer.
pstreef
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Mar 11, 2026
…veRecipe PR openrewrite#6810 changed DeclarativeRecipe.accumulator from a plain field to ThreadLocal to fix concurrent recipe runs overwriting each other's accumulator. However, ThreadLocal values are lost when execution resumes on a different thread after yielding. The accumulator is already stored on the rootCursor by ScanningRecipe.getAccumulator(), which is per-run and survives thread switches. This change removes the redundant ThreadLocal storage and instead resolves the accumulator from the rootCursor at visit time. The PreconditionBellwether now defers precondition resolution to visit time (when the rootCursor is available) rather than eagerly resolving in a field initializer.
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What's Changed
DeclarativeRecipe.accumulatoris a mutable field that gets set during the scan phase viagetInitialValue(). When the sameDeclarativeRecipeinstance is shared across concurrent recipe runs (e.g. via a recipe cache in the Moderne worker), one run's scan phase overwrites the accumulator set by another run. This causes the second run to use stale or null accumulator state during the edit phase, resulting in precondition scanning recipes producing incorrect results — typically 0 file changes for the losing run.Changes
accumulatorfield fromAccumulatortoThreadLocal<Accumulator>so each run thread gets its own independent accumulatorgetInitialValue()to useaccumulator.set(acc)orVisitors()to useaccumulator.get()with a null guardclone()to create a freshThreadLocalfor cloned instancesHow to Reproduce
DeclarativeRecipeinstance for the same recipe IDUpgradeSpringBoot_3_4) concurrently via two paths — one direct catalog run, one wrapped in a builder/YAML declarative recipeTest Plan
rewrite-core:testpasses