Spring WebClient reactor.netty.internal.shaded.reactor.pool.PoolAcquireTimeoutException

Question

I am using Spring WebClient to call a rest service. The code for the post call as mentioned below.

Mono<ClientResponse> response = client.post()
                        .uri(uriBuilder -> uriBuilder.build())
                        .headers(httpHeaders -> httpHeaders.setAll(getHeaders()))
                        .body(BodyInserters.fromPublisher(Mono.just(message), String.class))
                        .exchange();
                response.subscribe(clientResponse -> {
                   System.out.println(clientResponse.statusCode());
                });

I am getting the following exception after posting continuously for a while (after posting 2-3 million requests in 5 mins).

 [     parallel-3] r.c.s.Schedulers                         : Scheduler worker in group main failed with an uncaught exception

reactor.core.Exceptions$ErrorCallbackNotImplemented: reactor.netty.internal.shaded.reactor.pool.PoolAcquireTimeoutException: Pool#acquire(Duration) has been pending for more than the configured timeout of 45000ms
Caused by: reactor.netty.internal.shaded.reactor.pool.PoolAcquireTimeoutException: Pool#acquire(Duration) has been pending for more than the configured timeout of 45000ms
    at reactor.netty.internal.shaded.reactor.pool.AbstractPool$Borrower.run(AbstractPool.java:317) ~[reactor-netty-0.9.0.RELEASE.jar!/:0.9.0.RELEASE]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
Error has been observed at the following site(s):
    |_ checkpoint ⇢ Request to POST https://myrest-service-c12-1-lb-125370128.us-west-2.elb.amazonaws.com/antenna [DefaultWebClient]
Stack trace:
        at reactor.netty.internal.shaded.reactor.pool.AbstractPool$Borrower.run(AbstractPool.java:317) ~[reactor-netty-0.9.0.RELEASE.jar!/:0.9.0.RELEASE]
        at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:68) [reactor-core-3.3.0.RELEASE.jar!/:3.3.0.RELEASE]
        at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:28) [reactor-core-3.3.0.RELEASE.jar!/:3.3.0.RELEASE]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:834) [?:?]

It looks like the pool is exhausted and I need to limit the number of requests. Could some one help me in solving this issue. Thanks in advance.

Answer 1

Seems to be a bug in reactor-netty that has recently been fixed: https://github.com/reactor/reactor-netty/issues/1012