How to get thread information logs when calling publishOn - project-reactor

Question

I am working on Schedulers in reactive streams and using a Flux and Scheduler on this Flux using the publishOn method as follows:
System.out.println("*********Calling Concurrency************");
List<Integer> elements = new ArrayList<>();
Flux.range(1, 1000)
.log()
.map(i -> i * 2)
.publishOn(Schedulers.parallel())
//.subscribeOn(Schedulers.parallel())
.subscribe(elements::add);
System.out.println("-------------------------------------");
for which i got the following info logs:
*********Calling Concurrency************
[info] | onSubscribe([Synchronous Fuseable] FluxRange.RangeSubscription)
[info] | request(256)
[info] | onNext(1)
[info] | onNext(2)
[info] | onNext(3)
[info] | onNext(4)
[info] | onNext(5)
[info] | onNext(6)
[info] | onNext(7)
[info] | onNext(8)
[info] | onNext(9)
.....
.....
[info] | onNext(444)
[info] | onNext(445)
[info] | onNext(446)
[info] | onNext(447)
[info] | onNext(448)
-------------------------------------
[info] | request(192)
.....
.....
[info] | onNext(999)
[info] | onNext(1000)
[info] | onComplete()
[info] | request(192)
and there is no information about the thread execution and processing.
Also, sometimes 192 elements are requested and sometimes 256 elements are requested.
Here is the dependency which i am using:
<dependency>
<groupId>com.googlecode.slf4j-maven-plugin-log</groupId>
<artifactId>slf4j-maven-plugin-log</artifactId>
<version>1.0.0</version>
</dependency>
How can i get the log information about the current thread/parallel thread execution?
Please suggest.

Answer 1

This looks like a logger misconfiguration on your side.
Reactor will pick up that you use SLF4J but you still need a correctly configured logging implementation, like Logback,and associated appenders that will log the thread name.
If you don't want to bother at all with a logging framework, you can call Loggers.useConsoleLoggers() and it will print on the console in a simplified format that includes the current thread name. I recommend to only do that for a 1 shot run (like a debugging session) though, not in production code...

Answer 2

To get all required information just put .log() after .publishOn()
Flux.range(1, 1000)
.map(i -> i * 2)
.publishOn(Schedulers.parallel())
//.subscribeOn(Schedulers.parallel())
.log()
.blockLast();
the final output will look next:
12:13:21.964 [main] DEBUG reactor.util.Loggers$LoggerFactory - Using Slf4j logging framework
12:13:21.997 [main] INFO reactor.Flux.PublishOn.1 - | onSubscribe([Fuseable] FluxPublishOn.PublishOnSubscriber)
12:13:21.999 [main] INFO reactor.Flux.PublishOn.1 - | request(unbounded)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(2)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(4)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(6)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(8)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(10)
12:13:22.002 [parallel-1] INFO reactor.Flux.PublishOn.1 - | onNext(12)
so in that case information about Thread will be there
Note: Output might varying depends on used Logger library