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Reactor 多任务执行

​​​​​​​六七十三 人气:3

1 场景

调用多个平级服务,按照服务优先级返回第一个有效数据。

具体case:一个页面可能有很多的弹窗,弹窗之间又有优先级。每次只需要返回第一个有数据的弹窗。但是又希望所有弹窗之间的数据获取是异步的。这种场景使用 Reactor 怎么实现呢?

2 创建 service

2.1 创建基本接口和实体类

public interface TestServiceI {
    Mono request();
}

提供一个 request 方法,返回一个 Mono 对象。

@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class TestUser {
    private String name;
}

2.2 创建 service 实现

@Slf4j
public class TestServiceImpl1 implements TestServiceI {
    @Override
    public Mono request() {
        log.info("execute.test.service1");
        return Mono.fromSupplier(() -> {
                    try {
                        System.out.println("service1.threadName=" + Thread.currentThread().getName());
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    return "";
                })
                .map(name -> {
                    return new TestUser(name);
                });
    }
}

第一个 service 执行耗时 500ms。返回空对象;

创建第二个 service 执行耗时 1000ms。返回空对象;代码如上,改一下sleep时间即可。

继续创建第三个 service 执行耗时 1000ms。返回 name3。代码如上,改一下 sleep 时间,以及返回为 name3。

3 主体方法

public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        TestServiceI testServiceImpl4 = new TestServiceImpl4();
        TestServiceI testServiceImpl5 = new TestServiceImpl5();
        TestServiceI testServiceImpl6 = new TestServiceImpl6();
        List<TestServiceI> serviceIList = new ArrayList<>();
        serviceIList.add(testServiceImpl4);
        serviceIList.add(testServiceImpl5);
        serviceIList.add(testServiceImpl6);

    // 执行 service 列表,这样有多少个 service 都可以
        Flux<Mono<TestUser>> monoFlux = Flux.fromIterable(serviceIList)
                .map(service -> {
                    return service.request();
                });
    // flatMap(或者flatMapSequential) + map 实现异常继续下一个执行
        Flux flux = monoFlux.flatMapSequential(mono -> {
            return mono.map(user -> {
                        TestUser testUser = JsonUtil.parseJson(JsonUtil.toJson(user), TestUser.class);
                        if (Objects.nonNull(testUser) && StringUtils.isNotBlank(testUser.getName())) {
                            return testUser;
                        }
            // null 在 reactor 中是异常数据。
                        return null;
                    })
                    .onErrorContinue((err, i) -> {
                        log.info("onErrorContinue={}", i);
                    });
        });
        Mono mono = flux.elementAt(0, Mono.just(""));
        Object block = mono.block();
        System.out.println(block + "blockFirst 执行耗时ms:" + (System.currentTimeMillis() - startTime));
    }

执行输出:

20:54:26.512 [main] DEBUG reactor.util.Loggers - Using Slf4j logging framework
20:54:26.553 [main] INFO com.geniu.reactor.TestServiceImpl1 - execute.test.service1
service1.threadName=main
20:54:27.237 [main] INFO com.geniu.reactor.TestReactorOrderV2 - onErrorContinue=TestUser(name=)
20:54:27.237 [main] INFO com.geniu.reactor.TestServiceImpl2 - execute.test.service2
service5.threadName=main
20:54:28.246 [main] INFO com.geniu.reactor.TestReactorOrderV2 - onErrorContinue=TestUser(name=)
20:54:28.246 [main] INFO com.geniu.reactor.TestServiceImpl3 - execute.test.service3
service6.threadName=main
TestUser(name=name3)blockFirst 执行耗时ms:2895

总结:这样实现按照顺序返回第一个正常数据。但是执行并没有异步。下一步:如何实现异步呢?

4 实现异步

4.1 subcribeOn 实现异步

修改 service 实现。增加 .subscribeOn(Schedulers.boundedElastic())

如下:

@Slf4j
public class TestServiceImpl1 implements TestServiceI {
    @Override
    public Mono request() {
        log.info("execute.test.service1");
        return Mono.fromSupplier(() -> {
                    try {
                        System.out.println("service1.threadName=" + Thread.currentThread().getName());
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    return "";
                })
                //增加subscribeOn
                .subscribeOn(Schedulers.boundedElastic())
                .map(name -> {
                    return new TestUser(name);
                });
    }
}

再次执行输出如下:

21:02:04.213 [main] DEBUG reactor.util.Loggers - Using Slf4j logging framework
21:02:04.265 [main] INFO com.geniu.reactor.TestServiceImpl1 - execute.test.service1
service4.threadName=boundedElastic-1
21:02:04.300 [main] INFO com.geniu.reactor.TestServiceImpl2 - execute.test.service2
21:02:04.302 [main] INFO com.geniu.reactor.TestServiceImpl3 - execute.test.service3
service2.threadName=boundedElastic-2
service3.threadName=boundedElastic-3
21:02:04.987 [boundedElastic-1] INFO com.geniu.reactor.TestReactorOrderV2 - onErrorContinue=TestUser(name=)
21:02:05.307 [boundedElastic-2] INFO com.geniu.reactor.TestReactorOrderV2 - onErrorContinue=TestUser(name=)
TestUser(name=name6)blockFirst 执行耗时ms:1242

4.2 CompletableFuture 实现异步

修改 service 实现,使用 CompletableFuture 执行耗时操作(这里是sleep,具体到项目中可能是外部接口调用,DB 操作等);然后使用 Mono.fromFuture 返回 Mono 对象。

@Slf4j
public class TestServiceImpl1 implements TestServiceI{
    @Override
    public Mono request() {
        log.info("execute.test.service1");
        CompletableFuture<String> uCompletableFuture = CompletableFuture.supplyAsync(() -> {
            try {
                System.out.println("service1.threadName=" + Thread.currentThread().getName());
                Thread.sleep(500);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
            return "testname1";
        });

        return Mono.fromFuture(uCompletableFuture).map(name -> {
            return new TestUser(name);
        });
    }
}

执行返回如下:

21:09:59.465 [main] DEBUG reactor.util.Loggers - Using Slf4j logging framework
21:09:59.510 [main] INFO com.geniu.reactor.TestServiceImpl2 - execute.test.service2
service2.threadName=ForkJoinPool.commonPool-worker-1
21:09:59.526 [main] INFO com.geniu.reactor.TestServiceImpl3 - execute.test.service3
service3.threadName=ForkJoinPool.commonPool-worker-2
21:09:59.526 [main] INFO com.geniu.reactor.TestServiceImpl1 - execute.test.service1 
service1.threadName=ForkJoinPool.commonPool-worker-3
21:10:00.526 [ForkJoinPool.commonPool-worker-1] INFO com.geniu.reactor.TestReactorOrder - onErrorContinue=TestUser(name=)
21:10:00.538 [ForkJoinPool.commonPool-worker-2] INFO com.geniu.reactor.TestReactorOrder - onErrorContinue=TestUser(name=)
TestUser(name=testname1)blockFirst 执行耗时ms:1238

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