Virtual Threads, Structured Concurrency and Scoped Values: Putting it all together

Transcript

1. 1 Virtual Threads, Structured Concurrency and Scoped Values: Putting it all together Balkrishna Rawool
2. 2 Project Loom Purpose: Ø Supporting easy-to-use, high-throughput lightweight concurrency and new programming models for it Features: Ø Virtual Threads – Final in JDK 21 Ø Structured Concurrency – Preview Ø Scoped Values – Final in JDK 25
3. Virtual Threads
4. 4 Platform Threads and Virtual Threads JVM OS Platform Threads Platform Threads: Ø Thin wrapper over OS threads Ø One-to-one mapping with OS threads Ø Thread pools Virtual Threads Virtual Threads: Ø Lightweight user threads Ø Highly scalable Ø No need for pooling
5. 5 Virtual Thread Scheduler Platform/ Carrier Thread Virtual Threads
6. A simple web-app with virtual threads
7. 7 A simple web-app with virtual threads Ø SpringBoot App Ø SpringBoot 4.0 Ø JDK 26 Ø Domain: Banking Ø Name: A Bank
8. Structured Concurrency
9. 9 Structured Concurrency: Examples All these examples can be implemented using StructuredTaskScope API.
10. 10 Structured Concurrency: Continued Principle: Ø When flow of execution splits into multiple concurrent flows, they rejoin in the same code block Benefits: Ø Error handling with short-circuiting Ø Cancellation propagation Ø Clarity Ø Observability
11. Structured Concurrency API
12. 12 Feature: Loan application Ø Customer applies for loan Ø Get customer details Ø Using customer details Ø Get accounts Ø Get loans Ø Get credit scores Ø Two services provide this score Ø Response from one is enough Ø Aggregate all this info and send to offer-calculation service
13. 13 Feature: Loan application Get Customer Details Get Account Details Get Loan Details Get Credit Score Calculate Offer Get Credit Score Get Credit Score 1 Get Credit Score 2
14. Scoped Values
15. ThreadLocal 15 Ø Each thread gets its own copy of the object. Ø Useful for Ø Request/session-specific data Ø Caching Ø Observability (e.g. CorrelationID) Ø VirtualThread-s support ThreadLocal-s. Ø Problems Ø Unconstrained mutability Ø Unbounded lifetime Ø Expensive inheritance (with InheritableThreadLocal)
16. Scoped Values 16 Ø Immutable Ø All (allowed) threads use the same copy Ø Inherited through the StructuredTaskScope to the child-virtual-threads Ø Bounded by the scope ScopedValue VALUE = ScopedValue.newInstance(); ScopedValue.where(VALUE, someValue) .run(() -> {...});
17. Scoped Values API
18. Summary 18 Ø Virtual Threads enable high scalability Ø Structured Concurrency Ø Built with virtual threads as foundation Ø Provides structured approach for modelling concurrent tasks Ø Scoped Values Ø Better alternative to ThreadLocal Ø StructuredTaskScope enables “inheritance” of scoped-values
19. 19 Thank you!