聊聊reactive streams的parallel flux

序

本文主要研究下reactive streams的flux的parallel运行方式.

目的

在一些涉及IO操作，比如读取文件，访问数据库等，通常建议使用异步线程以parallel模式运行，以提升性能。

实例

    @Test
    public void testParallelRunOn(){
        Flux.range(1, 1000)
                .log()
                .parallel(8)
                .runOn(Schedulers.parallel()) //parallel flux
                .sequential() //必须使用sequential来将这些异步线程的执行结果汇集成一个stream
                .map(e -> {
                    LOGGER.info("map thread:{},e:{}",Thread.currentThread().getName(),e);
                    return e*10;
                })
                .subscribe(e -> {
                    LOGGER.info("subscribe thread:{},e:{}",Thread.currentThread().getName(),e);
                });
    }

部分输出

2:38:53.949 [main] INFO reactor.Flux.Range.1 - | onNext(13)
22:38:53.949 [parallel-2] INFO com.example.demo.ParallelTest - subscribe thread:parallel-2,e:120
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(14)
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - map thread:parallel-5,e:13
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - subscribe thread:parallel-5,e:130
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(15)
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - map thread:parallel-5,e:14
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - subscribe thread:parallel-5,e:140
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(16)
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - map thread:parallel-5,e:15
22:38:53.950 [parallel-5] INFO com.example.demo.ParallelTest - subscribe thread:parallel-5,e:150
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(17)
22:38:53.950 [parallel-8] INFO com.example.demo.ParallelTest - map thread:parallel-8,e:16
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(18)
22:38:53.950 [parallel-8] INFO com.example.demo.ParallelTest - subscribe thread:parallel-8,e:160
22:38:53.950 [parallel-8] INFO com.example.demo.ParallelTest - map thread:parallel-8,e:17
22:38:53.950 [main] INFO reactor.Flux.Range.1 - | onNext(19)
22:38:53.950 [parallel-8] INFO com.example.demo.ParallelTest - subscribe thread:parallel-8,e:170
22:38:53.950 [parallel-8] INFO com.example.demo.ParallelTest - map thread:parallel-8,e:18

小结

• parallel来指定线程池线程个数
• runOn启动parallel flux
• sequential将异步线程池执行结果汇集成一个stream

doc

• advanced-parallelizing-parralelflux