How to make mono timeout works - spring-webflow

Question

I'm first to use webflux in my project, just want to set timeout in case of long period handle.
#GetMapping("/{id}")
private Mono<ResponseEntity<String>> getEmployeeById(#PathVariable
String id) {
return Mono.just(id).map(updateTweet -> {
try {
TimeUnit.SECONDS.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
return new ResponseEntity<>(updateTweet, HttpStatus.OK);
}).timeout(Duration.ofSeconds(3)).onErrorReturn(new ResponseEntity<>("0000", HttpStatus.OK));
}
expect:in 3 seconds later, this function will return.
actual results: in 10 seconds later, this function returned.

Answer 1

In your code the .map and .timeout are all in subscription thread. The .sleep(10) causes the currently executing thread to sleep (temporarily cease execution) for the 10s. So when 3s timeout the thread can't execute.
You should use publishOn shifts .map to scheduler thread.
#GetMapping("/{id}")
private Mono<ResponseEntity<String>> getEmployeeById(#PathVariable
String id) {
Scheduler singleThread = Schedulers.single();
return Mono.just(id).publishOn(singleThread).map(updateTweet -> {
try {
TimeUnit.SECONDS.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
return new ResponseEntity<>(updateTweet, HttpStatus.OK);
}).timeout(Duration.ofSeconds(3)).onErrorReturn(new ResponseEntity<>("0000", HttpStatus.OK));
}

Answer 2

What TimeUnit.SECONDS.sleep(10) does is invoke Thread.sleep(). This puts the current
Thread into sleep mode for 10 seconds.
Since you are doing this inside a map, the Thread that goes to sleep is the current thread. The code that waits for a timeOut is also on the current thread and so doesn't come into effect until the sleep times out. For this reason, you should avoid performing any Thread related operations when doing reactive programming.
If you want to simulate a long running process in the above code, you could either invoke an external API that you control that waits more than 3 seconds before sending a response, or use one of the delay* operators.