What does timeout operator measure in Reactor and why it doesn't work in some cases? - spring-webflux

Question

Recently, a reactive piece of code results in timeout, it involves redis operation, like this:
redisOps.entries(key).map(...).map(...).switchIfEmpty().timeout();
In order to identify if timeout happens in redis query, I think timeout should be located after entries, in this way, map consumed time would not be monitored by timeout. So I made a guess, and wrote demo.
does timeout monitor data emission elapsed time until it, and data operations after it is not counted? For example, in the following code snippet, only time consumption in a and b are monitored by timeout, not including c or d.
Mono mono = foo();
mono.a().b().timeout().c().d();
Why in the following code, timeout does not work.
Mono.just("good luck")
.map(s -> {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "timeout 1";
})
.map(s->{
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "timeout 2";
})
.timeout(Duration.ofSeconds(1))
.subscribe(System.out::println);
compared with item 2, timeout in the following code works:
public static void main(String[] args) {
Mono.fromCallable(() -> {
log.info("begin 1");
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("return 1");
return "good luck 1";
})
.timeout(Duration.ofMillis(1500l))
.map((s) -> {
log.info("begin 2");
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("return 2");
return "good luck 2";
})
.subscribe(System.out::println);
}

Answer 1

Anwser the comment's question, some operator is eager, it will execute at assembly stage. you can use some lazy operator, eg: defer、fromSupplier...
public Mono<?> defaultData() {
return Mono.defer(() -> {
//do Something
return ...
});
}
Here are some demo(https://github.com/echooymxq/reactive-study).