Spring Boot 2.5.8 graceful shutdown - java.util.concurrent.RejectedExecutionException

[michalstefanext]

I am not 100% sure if this is an issue, but every time I shutdown the spring boot application (version 2.5.8) using:

• spring.cloud.gcp.pubsub v3.1.0
• having subscriber using PubSubInboundChannelAdapter (spring integration)
• using server.shutdown=graceful for spring boot app

I get this exception from Subscriber:

Exception in thread "Thread-35" java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@3d8416eb[Not completed, task = java.util.concurrent.Executors$RunnableAdapter@705df4f2[Wrapped task = com.google.common.util.concurrent.ListenerCallQueue$PerListenerQueue@5de316dd]] rejected from java.util.concurrent.ScheduledThreadPoolExecutor@54d338fa[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 2]
	at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2065)
	at java.base/java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:833)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:340)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:562)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.execute(ScheduledThreadPoolExecutor.java:705)
	at com.google.common.util.concurrent.ListenerCallQueue$PerListenerQueue.dispatch(ListenerCallQueue.java:170)
	at com.google.common.util.concurrent.ListenerCallQueue.dispatch(ListenerCallQueue.java:121)
	at com.google.common.util.concurrent.AbstractService.dispatchListenerEvents(AbstractService.java:516)
	at com.google.common.util.concurrent.AbstractService.notifyFailed(AbstractService.java:479)
	at com.google.api.core.AbstractApiService$InnerService.innerNotifyFailed(AbstractApiService.java:165)
	at com.google.api.core.AbstractApiService$InnerService.access$400(AbstractApiService.java:145)
	at com.google.api.core.AbstractApiService.notifyFailed(AbstractApiService.java:142)
	at com.google.cloud.pubsub.v1.Subscriber.access$1900(Subscriber.java:91)
	at com.google.cloud.pubsub.v1.Subscriber$2.run(Subscriber.java:303)
	at java.base/java.lang.Thread.run(Thread.java:833)

Process finished with exit code 130

Is there a way how to make it shutdown gracefully without exception please?

[elefeint]

RejectedExecutionException means the threadpool is in the process of gracefully shutting down, but was asked to do additional work, and firmly said no.

On the one hand, this is not a problem because it's a normal scenario -- a Pub/Sub message is trying to come in from a gRPC stream. On the other hand, we should probably try to shut down the adapter before the thread pool itself closes to avoid cluttering your logs with exceptions.

[michalstefanext]

Thanks @elefeint (btw looks like it happens every time, no matter if there's a message coming in from gRPC stream or not).

[meltsufin]

Thanks for the update! Would you be able to provide some sample code that reproduces this error? Thanks!

[michalstefanext]

Apologies @meltsufin, we've switched from spring-integration to use spring-cloud-gcp-pubsub directly, so we're no longer facing this issue + we have removed the branch with previous spring-integration code, so I believe it will be better to close this issue, but thanks for your help!