Facing issues while implementing graceful shutdown feature - spring-boot

Question

I am working on standalone spring boot application and used spring integration channel architecture to transfer files from source to destination.
We have provided multi-instance feature as well, to achieve this we will be locking(append .lock for the files) files for particular instance to restrict access from other instance.
Currently, I have one requirement for graceful shutdown . I implemented but end-up with the following error. Can anyone help me on this ?
Control bus configuration :
<integration:channel id="controlChannel" />
<integration:control-bus input-channel="controlChannel" />
Adapter configuration :
<file:inbound-channel-adapter id="filesInChannel"
directory="path" auto-startup="false" scanner="recursiveScanner"
auto-create-directory="true">
<integration:poller id="poller"
max-messages-per-poll="5" fixed-rate="1000"
task-executor="pollingExecutor">
<integration:transactional
transaction-manager="transactionManager" />
</integration:poller>
</file:inbound-channel-adapter>
Method added for graceful shutdown component
#PreDestroy
public void onDestroy() throws InterruptedException {
try {
inboundFileAdapterChannel.send(new GenericMessage<String>("#'filesInChannel.adapter'.stop()"));
} catch (Exception e) {
e.printStackTrace();
}
// wait till current processing of files is over
pollingExecutor.shutdown();
pollingExecutor.setWaitForTasksToCompleteOnShutdown(Boolean.TRUE);
System.out.println("Application shutdown succesfully");
}
Error Trace :
org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application.controlChannel'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload=#'filesInChannel.adapter'.stop(), headers={id=5f0282c5-5a02-3f57-3056-948dd74a8d72, timestamp=1559894703464}], failedMessage=GenericMessage [payload=#'filesInChannel.adapter'.stop(), headers={id=5f0282c5-5a02-3f57-3056-948dd74a8d72, timestamp=1559894703464}]
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:445)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:394)
at com.openbank.interfaces.file.handler.GracefulShutdownHook.onDestroy(GracefulShutdownHook.java:63)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:365)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeDestroyMethods(InitDestroyAnnotationBeanPostProcessor.java:323)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeDestruction(InitDestroyAnnotationBeanPostProcessor.java:155)
at org.springframework.beans.factory.support.DisposableBeanAdapter.destroy(DisposableBeanAdapter.java:240)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroyBean(DefaultSingletonBeanRegistry.java:577)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingleton(DefaultSingletonBeanRegistry.java:549)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingleton(DefaultListableBeanFactory.java:957)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingletons(DefaultSingletonBeanRegistry.java:510)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingletons(DefaultListableBeanFactory.java:964)
at org.springframework.context.support.AbstractApplicationContext.destroyBeans(AbstractApplicationContext.java:1041)
at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1017)
at org.springframework.context.support.AbstractApplicationContext$1.run(AbstractApplicationContext.java:937)
Caused by: org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload=#'filesInChannel.adapter'.stop(), headers={id=5f0282c5-5a02-3f57-3056-948dd74a8d72, timestamp=1559894703464}]
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:138)
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:105)
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:73)
... 19 more

Answer 1

#PreDestroy is too late to perform such operations.
By that time all Lifecyle beans will have been stop()ped (which unsubscribes from the channel).
You need to perform that work using some other signal.
You could implement SmartLifecyle and put your bean in a late phase (so it is stop()ped early.