Spring Integration - how to delegate error handling to separate thread - error-handling

Question

My Spring Integration Flow looks like the below,
Read file from directory
Add a header called errorChannel:'exceptionChannel' to the message
Perform business logic
Print output to a 'success directory'
If there is an error on step 3, the exception is sent to the exceptionChannel,and is written to a 'failed directory'.
I want the error flow to be delegated to a separate thread.
What I have:
If there are 5 files and the third file has an error,
-> 2 files are written to the success directory
-> 1 file is written to the failed directory.
-> The flow stops after the error file.
What I need:
If there are 5 files and the third file has an error,
-> First 2 files must be written to success directory
-> 3rd file must be written to failed directory
-> Last 2 files must be written to success directory
Code for Success flow:
#Bean(name="exceptionChannel")
MessageChannel exceptionChannel() {
return MessageChannels.direct()
.get();
}
#Bean
public IntegrationFlow migrateInputToOutput() {
return IntegrationFlows.from(Files.inboundAdapter(new File(INPUT_DIR))),
.enrichHeaders(h -> h.header("errorChannel", "exceptionChannel", true))
.handle(someBusinessLogic) // ANY EXCEPTION HERE IS SENT TO exceptionChannel
.handle(Files.outboundAdapter(new File(OUTPUT_SUCCESS_DIR))
.get();
}
Code for handling error:
#Bean
public IntegrationFlow handleErrorInMigration() {
return IntegrationFlows.from("exceptionChannel"),
.handle(errorLogicToPrintException)
.handle(Files.outboundAdapter(new File(OUTPUT_ERROR_DIR))
.get();
}

Answer 1

The Files.inboundAdapter() is pollable source, so there is somewhere something like Poller configured in your code. That one has a errorChannel() option. It is really would be better to do that way. If your poller is global one and you don't want to modify it, it is better to have a poller configured exactly for this endpoint:
IntegrationFlows.from(Files.inboundAdapter(new File(INPUT_DIR)),
e -> e.poller(p -> p.fixedDelay().errorChannel(exceptionChannel())))
This way you won't effect all other polling endpoints.
To move your error handling to different thread, you need to consider to make that exceptionChannel as an ExecutorChannel:
#Bean(name="exceptionChannel")
MessageChannel exceptionChannel() {
return MessageChannels.executor(myExecutor)
.get();
}