What is the difference between Schedulers.newElastic and Schedulers.elastic methods?

Question

I am working on Flux and Mono and using them in multi threaded environment and using the Schedular which provide the worker thread.

There are many options to start the Schedular using elastic, parallel and newElastic.

Here is the code which i used:

    System.out.println("------ elastic ---------  ");
    Flux.range(1, 10)
      .map(i -> i / 2)
      .publishOn(Schedulers.elastic()).log()
      .blockLast();
    
    System.out.println("------ new elastic ---------  ");
    Flux.range(1, 10)
      .map(i -> i / 2).log()
      .publishOn(Schedulers.newElastic("my")).log()
      .blockLast();

and both of them have the same documentation:

Scheduler that dynamically creates ExecutorService-based Workers and caches the thread pools, reusing them once the Workers have been shut down.

The maximum number of created thread pools is unbounded.

The default time-to-live for unused thread pools is 60 seconds, use the appropriate factory to push a different value.

This scheduler is not restartable.

and here is the logs for both of them:

------ elastic ---------  
[ INFO] (main) | onSubscribe([Fuseable] FluxPublishOn.PublishOnSubscriber)
[ INFO] (main) | request(unbounded)
[ INFO] (elastic-2) | onNext(0)
[ INFO] (elastic-2) | onNext(1)
[ INFO] (elastic-2) | onNext(1)
[ INFO] (elastic-2) | onNext(2)
[ INFO] (elastic-2) | onNext(2)
[ INFO] (elastic-2) | onNext(3)
[ INFO] (elastic-2) | onNext(3)
[ INFO] (elastic-2) | onNext(4)
[ INFO] (elastic-2) | onNext(4)
[ INFO] (elastic-2) | onNext(5)
[ INFO] (elastic-2) | onComplete()
------ new elastic ---------  
[ INFO] (main) | onSubscribe([Fuseable] FluxMapFuseable.MapFuseableSubscriber)
[ INFO] (main) | onSubscribe([Fuseable] FluxPublishOn.PublishOnSubscriber)
[ INFO] (main) | request(unbounded)
[ INFO] (main) | request(256)
[ INFO] (main) | onNext(0)
[ INFO] (main) | onNext(1)
[ INFO] (my-4) | onNext(0)
[ INFO] (main) | onNext(1)
[ INFO] (my-4) | onNext(1)
[ INFO] (main) | onNext(2)
[ INFO] (my-4) | onNext(1)
[ INFO] (my-4) | onNext(2)
[ INFO] (main) | onNext(2)
[ INFO] (main) | onNext(3)
[ INFO] (my-4) | onNext(2)
[ INFO] (main) | onNext(3)
[ INFO] (my-4) | onNext(3)
[ INFO] (my-4) | onNext(3)
[ INFO] (main) | onNext(4)
[ INFO] (my-4) | onNext(4)
[ INFO] (main) | onNext(4)
[ INFO] (main) | onNext(5)
[ INFO] (my-4) | onNext(4)
[ INFO] (main) | onComplete()
[ INFO] (my-4) | onNext(5)
[ INFO] (my-4) | onComplete()

What is the difference between the two?

Answer 1

The elastic() function returns a shared scheduler instance. This means that multiple calls to this function will return the same scheduler.

The functions prefixed with new will always create a new scheduler instance.

Check the docs for the Schedulers class here: https://projectreactor.io/docs/core/release/api/