Claude
a7b76243fa
Covers replacing Thread.sleep with await() across a void @Async method, an @EmbeddedKafka-backed @KafkaListener, and an already-running @Scheduled job; verifies Awaitility 4.3.0's real defaults (10s timeout, 100ms poll interval) and its default-uncaught-exception-handler swap directly against the jar; and documents a real pom.xml trap where Boot 4.1.1 split Kafka's autoconfiguration (spring-boot-kafka) out of spring-kafka itself, which silently leaves @KafkaListener beans with no running container.
4.0 KiB
spring-async-demo
Companion code for the asynchronous execution and scheduling series on
ankurm.com. Each
directory is a self-contained Maven project for one article, with its own pom.xml, its own
numbered documentation chapters, and its own captured output under docs/output/ — regenerated
by that module's scripts/run-all.sh, never typed by hand.
| Module | Article | What it demonstrates |
|---|---|---|
async/ |
@Async in Spring Boot 4: Executors, Virtual Threads and the Self-Invocation Trap | Which thread a method actually ran on, in every case where the answer is not the one you expect |
scheduling/ |
@Scheduled, ShedLock and Distributed Cron: Scheduling That Survives Three Replicas | Three replicas against one database running the same job three times, then one row and one conditional UPDATE fixing it |
awaitility/ |
Testing Asynchronous Code with Awaitility (@Async, Kafka Listeners, Schedulers) | Replacing Thread.sleep with await() across a void @Async method, an @KafkaListener, and a @Scheduled job — plus the real pom.xml trap where Boot 4.1.1 split Kafka's autoconfiguration out of spring-boot-autoconfigure |
virtual-threads-benchmark/ |
Virtual Threads on Spring Boot 4.1: The Benchmarks, Re-Run, and the Pinning Advice That Expired | 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 |
virtual-threads-benchmark-webflux/ |
Virtual Threads vs Reactive (WebFlux) vs Platform Threads: Benchmarks and a Decision Framework | The WebFlux leg of the three-way comparison, plus the event-loop-starvation failure mode an isolated CPU benchmark can't show |
Common ground
All modules target the same verified stack: JDK 25 (Temurin 25.0.4.1+1), Spring Boot
4.1.1, Spring Framework 7.0.9. Versions were read from maven-metadata.xml on Maven Central
and from Boot's own spring-boot-dependencies POM, rather than from release announcements.
Everything is asserted by a test and captured to a file. The measurement is nearly always the same
one: the name of the thread that ran the work, returned by the code itself. Timing cannot tell a
fast synchronous call from an asynchronous one, which is why @Async failures survive so long in
production.
The two modules share a mechanism, which is why they live together: both @Async and ShedLock's
default PROXY_METHOD intercept mode are Spring AOP proxies. Every proxy limitation the async
module measures — self-invocation, final methods — applies unchanged to a
@SchedulerLock method, and silently produces an unlocked job rather than a synchronous one.
The scheduling module also needs a database. scheduling/scripts/postgres.sh unpacks a
throwaway PostgreSQL 14 into target/ with no Docker and no root, which is how its transcripts
were produced; docker-compose.yml is there for anyone who would rather use Docker.
virtual-threads-benchmark and virtual-threads-benchmark-webflux are a similar pair: the
first re-benchmarks platform threads against virtual threads for one post, the second adds the
WebFlux leg for a different, three-way-comparison post, and reuses the first module's
committed transcripts rather than re-measuring the same thing twice. Both use the same
client-side load generator (java.net.http.HttpClient on a virtual-thread executor, client
role only) so all three threading models in the three-way post are measured the same way.
Licence
MIT — see LICENSE.