Claude
09631dcaab
Fixes found during self-correction before publishing: - /stream used Flux.interval(), which ticks on its own wall-clock schedule independent of downstream demand and threw OverflowException under a slow subscriber; switched to Flux.range(), which has no independent production schedule and can never outrun demand. - Single-trial HTTP load tests on this shared sandbox swung by more than 50% run to run (795ms-1247ms observed on the identical /io endpoint back to back) -- large enough to flip which threading model looked faster. Fixed by taking the median of 5 independent trials for the I/O-bound benchmark and the median of 3 for the event-loop-starvation benchmark, rather than reporting a single noisy run as if it were precise. - The event-loop-starvation test's first cut used only 8 concurrent /cpu requests as background load, which drained through the 4 event-loop threads well inside the /io measurement window and produced an inconsistent, sometimes-inverted result across runs; raising to 60 fixed the under-loading problem but still flaked once during verification (372ms vs 374ms p99, a real tie). Final fix: 150 concurrent requests plus the median-of-3 trials above. Also adds StreamBackpressureTest, a StepVerifier proof that the /stream endpoint never emits ahead of its subscriber's outstanding requests, and updates the module's docs to report the de-noised numbers with an explicit methodology note on how they compare to the single-trial platform/virtual- thread numbers reused from a different post.
46 lines
3.6 KiB
Markdown
46 lines
3.6 KiB
Markdown
# spring-async-demo
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Companion code for the asynchronous execution and scheduling series on
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[ankurm.com](https://ankurm.com). Each
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directory is a self-contained Maven project for one article, with its own `pom.xml`, its own
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numbered documentation chapters, and its own captured output under `docs/output/` — regenerated
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by that module's `scripts/run-all.sh`, never typed by hand.
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| Module | Article | What it demonstrates |
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|---|---|---|
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| [`async/`](async/README.md) | [@Async in Spring Boot 4: Executors, Virtual Threads and the Self-Invocation Trap](https://ankurm.com/spring-boot-4-async-executors-virtual-threads/) | Which thread a method actually ran on, in every case where the answer is not the one you expect |
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| [`scheduling/`](scheduling/README.md) | [@Scheduled, ShedLock and Distributed Cron: Scheduling That Survives Three Replicas](https://ankurm.com/spring-scheduled-shedlock-distributed-cron/) | Three replicas against one database running the same job three times, then one row and one conditional UPDATE fixing it |
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| [`virtual-threads-benchmark/`](virtual-threads-benchmark/README.md) | [Virtual Threads on Spring Boot 4.1: The Benchmarks, Re-Run, and the Pinning Advice That Expired](https://ankurm.com/leveraging-virtual-threads-in-spring-boot-3-4-building-high-throughput-services/) | Platform threads vs virtual threads, re-benchmarked on Boot 4.1.1 / JDK 25, plus JEP 491's fix to `synchronized` pinning proven against a real JDK |
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| [`virtual-threads-benchmark-webflux/`](virtual-threads-benchmark-webflux/README.md) | [Virtual Threads vs Reactive (WebFlux) vs Platform Threads: Benchmarks and a Decision Framework](https://ankurm.com/virtual-threads-vs-webflux-vs-platform-threads-spring-boot-benchmarks/) | The WebFlux leg of the three-way comparison, plus the event-loop-starvation failure mode an isolated CPU benchmark can't show |
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## Common ground
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All modules target the same verified stack: **JDK 25** (Temurin 25.0.4.1+1), **Spring Boot
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4.1.1**, **Spring Framework 7.0.9**. Versions were read from `maven-metadata.xml` on Maven Central
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and from Boot's own `spring-boot-dependencies` POM, rather than from release announcements.
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Everything is asserted by a test and captured to a file. The measurement is nearly always the same
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one: the name of the thread that ran the work, returned by the code itself. Timing cannot tell a
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fast synchronous call from an asynchronous one, which is why `@Async` failures survive so long in
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production.
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The two modules share a mechanism, which is why they live together: both `@Async` and ShedLock's
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default `PROXY_METHOD` intercept mode are Spring AOP proxies. Every proxy limitation the `async`
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module measures — self-invocation, `final` methods — applies unchanged to a
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`@SchedulerLock` method, and silently produces an unlocked job rather than a synchronous one.
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The `scheduling` module also needs a database. `scheduling/scripts/postgres.sh` unpacks a
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throwaway PostgreSQL 14 into `target/` with no Docker and no root, which is how its transcripts
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were produced; `docker-compose.yml` is there for anyone who would rather use Docker.
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`virtual-threads-benchmark` and `virtual-threads-benchmark-webflux` are a similar pair: the
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first re-benchmarks platform threads against virtual threads for one post, the second adds the
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WebFlux leg for a different, three-way-comparison post, and reuses the first module's
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committed transcripts rather than re-measuring the same thing twice. Both use the same
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client-side load generator (`java.net.http.HttpClient` on a virtual-thread executor, client
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role only) so all three threading models in the three-way post are measured the same way.
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## Licence
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MIT — see [LICENSE](LICENSE).
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