Why Repeated Custom ThreadPools Trigger Java OOM and How to Fix It
Creating a new ThreadPoolExecutor with 10 core threads, 50 maximum threads, and a 2‑second keep‑alive for each request prevents core threads from being reclaimed, quickly exhausting native thread resources and causing an OutOfMemoryError.
If a custom ThreadPoolExecutor is instantiated for every test request with 10 core threads, a maximum of 50 threads, and a 2‑second keep‑alive time, the pool will not be reclaimed and will eventually cause an OutOfMemoryError.
Even though the pool is custom, core threads are never reclaimed. Each request creates a new pool with ten core threads; as request volume grows, thousands of threads accumulate, exhausting the JVM’s native thread limit.
Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native threadThe reason the ThreadPoolExecutor cannot be garbage‑collected is that its worker threads are inner classes ( Worker ) that hold an implicit reference to the executor. As long as any worker thread is alive (i.e., still running), the executor remains reachable, preventing reclamation.
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JavaEdge
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