Spring Reactor scheduler lock

Question

Can any one explain why this code never ends (always throws TimeoutException), 3.0.7 and 3.1.0.M3 all the same ? I thought remaining 4 threads will do their work piece-by-piece.

private static class Holder {
    private final int group, idx;

    Holder(int group, int idx) {
        this.group = group;
        this.idx = idx;
    }
}

private static final Logger log = LoggerFactory.getLogger(RxTest2.class);

@Test
public void test1() throws Exception {
    final Scheduler scheduler = Schedulers.parallel();
    final AtomicInteger c = new AtomicInteger();

    Flux.range(0, 8).flatMap(gi -> Flux.range(0, 30).map(i -> new Holder(gi, i)))
        .groupBy(h -> h.group)

        .parallel()
        .runOn(scheduler)

        .flatMap(chunk -> {

            log.debug("chunk {}", chunk.key());

            chunk
                .parallel()
                .runOn(scheduler)
                .flatMap(h -> {
                    log.debug("{} - {}", h.group, h.idx);
                    c.incrementAndGet();
                    return Mono.just(true);
                })
                .sequential()
                .blockLast();

            return Mono.just(true);
        })
        .sequential()
        .timeout(Duration.ofSeconds(2))
        .doOnTerminate(() -> log.debug("count: {}", c.get()))
        .blockLast();
}

if I split it to separate schedulers (Schedulers.newParallel("p1", 8), Schedulers.newParallel("p2")) - all is OK

Is there some special rule for counting number of threads for scheduler?

Answer 1

您似乎在Schedulers.parallel（）上运行了多个并行计算，并且它们完全饱和了调度程序，因此没有线程可用于处理.flatMap(chunk -> 。这里有线程饥饿的情况。只需删除内部chunk.parallel ，不需要这样做，因为计算已经是并行的。