java 限制Reactor的请求速率

o3imoua4  于 2023-02-20  发布在  Java
关注(0)|答案(2)|浏览(182)

我正在使用project reactor从一个使用rest的web服务加载数据。这是通过多个线程并行完成的。我开始达到web服务的速率限制,所以我希望每秒最多发送10个请求以避免这些错误。我该如何使用reactor来实现这一点呢?
使用zipWith(Mono.delayMillis(100))?或者有更好的方法吗?
谢谢

4sup72z8

4sup72z81#

您可以使用delayElements而不是整个zipwith

9gm1akwq

9gm1akwq2#

我们可以使用Flux.delayElements每1秒处理一批10个请求;请注意,如果处理时间超过1秒,下一批仍将并行启动,因此将与前一批一起处理(可能还有许多其他前一批)!
这就是为什么我提出了另一种解决方案,其中10个请求的批处理仍然每1秒处理一次,但是如果其处理时间超过1秒,则下一批将失败(参见overflowIllegalStateException);可以处理该故障,以便继续整个处理,但我不会在这里显示,因为我希望保持示例简单;请参阅onErrorResume对处理overflowIllegalStateException的有用性。
下面的代码将以每秒10个请求的速率在https://www.google.com/上执行GET。您必须做一些额外的修改,以支持服务器无法在1秒内处理所有10个请求的情况;当你的服务器还在处理前一秒发出的请求时,你可以跳过发送请求。

@Test
void parallelHttpRequests() {
    // this is just for limiting the test running period otherwise you don't need it
    int COUNT = 2;

    // use whatever (blocking) http client you desire;
    // when using e.g. WebClient (Spring, non blocking client)
    // the example will slightly change for no longer use
    // subscribeOn(Schedulers.elastic())
    RestTemplate client = new RestTemplate();
    
    // exit, lock, condition are provided to allow one to run 
    // all this code in a @Test, otherwise they won't be needed
    var exit = new AtomicBoolean(false);
    var lock = new ReentrantLock();
    var condition = lock.newCondition();

    MessageFormat message = new MessageFormat("#batch: {0}, #req: {1}, resultLength: {2}");
    Flux.interval(Duration.ofSeconds(1L))
            .take(COUNT) // this is just for limiting the test running period otherwise you don't need it
            .doOnNext(batch -> debug("#batch", batch)) // just for debugging
            .flatMap(batch -> Flux.range(1, 10) // 10 requests per 1 second
                            .flatMap(i -> Mono.fromSupplier(() ->
                                    client.getForEntity("https://www.google.com/", String.class).getBody()) // your request goes here (1 of 10)
                                    .map(s -> message.format(new Object[]{batch, i, s.length()})) // here the request's result will be the output of message.format(...)
                                    .doOnSubscribe(s -> debug("doOnSubscribe: #batch = " + batch + ", i = " + i)) // just for debugging
                                    .subscribeOn(Schedulers.elastic()) // one I/O thread per request
                            )
            )
            // consider using onErrorResume to handle overflow IllegalStateException
            .subscribe(
                    s -> debug("received", s) // do something with the above request's result
                    e -> {
                        // pay special attention to overflow IllegalStateException
                        debug("error", e.getMessage());
                        signalAll(exit, condition, lock);
                    },
                    () -> {
                        debug("done");
                        signalAll(exit, condition, lock);
                    }
            );

    await(exit, condition, lock);
}

// you won't need the "await" and "signalAll" methods below which
// I created only to be easier for one to run this in a test class

private void await(AtomicBoolean exit, Condition condition, Lock lock) {
    lock.lock();
    while (!exit.get()) {
        try {
            condition.await();
        } catch (InterruptedException e) {
            // maybe spurious wakeup
            e.printStackTrace();
        }
    }
    lock.unlock();
    debug("exit");
}

private void signalAll(AtomicBoolean exit, Condition condition, Lock lock) {
    exit.set(true);
    try {
        lock.lock();
        condition.signalAll();
    } finally {
        lock.unlock();
    }
}

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