CODEWITHSUNDEEP
springreactive-programmingblockingnonblockingreactor
iSmo
iSmo

Reputation: 310

Wrap blocking code into a Mono flatMap, is this still a non-blocking operation?

if i wrap blocking code into a flatMap, is this still a non-blocking operation ?

Example:

    public Mono<String> foo() {

    Mono.empty().flatMap(obj -> {

        try {

        Object temp = f.get();//are the thread at this point blocked or not ?

        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }

        return Mono.just("test");

    });

So, i think when i wrap blocking code into reactive code, the operation is still non-blocking ? If i am wrong, pls explain it to me.

Upvotes: 4

Views: 3348

Answers (1)

Yazan Jaber
Yazan Jaber

Reputation: 2068

if i wrap blocking code into a flatMap, is this still a non-blocking operation ?

flatMap doesn't create new threads for you. For example:

Mono.just("abc").flatMap(val -> Mono.just("cba")).subscribe();

All the code above will be executed by the current thread that called subscribe. So if the mapper function contained a long blocking operation the thread that called subscribe will be blocked as well.

To transform this to an asynchronous operation you can use subscribeOn(Schedulers.elastic());

 Mono.just("abc").flatMap(val -> Mono.just("cba")).subscribeOn(Schedulers.elastic());

Mono and Flux don't create threads, but some operators take Scheduler as an extra argument to use such as the interval operator, or alter threading model all together such as subscribeOn.

One extra thing, in your example the mapper function is never going to be called, since your applying flatMap to an empty mono which completes directly with no values emitted.

Upvotes: 6

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