Fix broken double-checked locking in the R2DBC connection factory#11913
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ivankrn wants to merge 1 commit into
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Fix broken double-checked locking in the R2DBC connection factory#11913ivankrn wants to merge 1 commit into
ivankrn wants to merge 1 commit into
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Signed-off-by: Ivan Kropotin <102463202+ivankrn@users.noreply.github.com>
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This PR fixes a thread-safety issue in TestcontainersR2DBCConnectionFactory caused by the incorrectly implemented double-checked locking.
According to Java's memory model, a concurrently used variable without a
volatilekeyword lacks happens-before semantics, so this can lead to visibility and/or instruction reordering issues, such as seeing stale values or intermittent exceptions. By addingvolatilebeforeCompletableFuture<R2DBCDatabaseContainer> futurewe ensure that it is visible to other threads immediately after its modification.Additionally, the
futureReftrick reduces volatile read overhead as described in Joshua Bloch's "Effective Java" (see this Oracle article for details), thereby increasing overall performance.