Introduction and pitfalls of virtual threads
summary
Java 21 adds virtual threads and structured concurrency and demonstrates that thousands scale: the demo creates 10,000 virtual threads demo on a laptop and benchmark shows 100,000 virtual threads ≈225MB where platform threads ran out of memory. Details cover carrier threads, mounting/unmounting stacks, pinning pitfalls (synchronized, JNI, certain file ops), a virtual-thread-per-task executor, run flags to detect pinning, and a custom StructuredTaskScope that cancels remaining tasks when a product <100 is found, which works as shown.
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chapters (13)
- 0:00Introduction to virtual threads
- 1:57Platform threads explained
- 4:28Limitations of platform threads
- 7:17Virtual threads introduction
- 10:12Creating virtual threads demo
- 13:44Scaling virtual threads demo
- 14:48How virtual threads work
- 18:21Pitfalls of virtual threads
- 21:09Structured concurrency explained
- 25:22Structured concurrency demo
- 29:37Custom structured concurrency
- 33:12Virtual threads takeaways
- 33:34Q&A session
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