Question

我正在使用Java 11的HttpClient将请求发布到HTTP2服务器。 HttpClient对象被创建为Singleton Spring bean，如下所示。

@Bean
    public HttpClient getClient() {
                return HttpClient.newBuilder().version(Version.HTTP_2).executor(Executors.newFixedThreadPool(20)).followRedirects(Redirect.NORMAL)
                .connectTimeout(Duration.ofSeconds(20)).build();
    }

I am using the sendAsync method to send the requests asynchronously.

When I try to hit the server continuously, I am receiving the error after certain time "java.io.IOException: too many concurrent streams". I used Fixed threadpool in the Client building to try to overcome this error, but it is still giving the same error.

The Exception stack is..

java.util.concurrent.CompletionException: java.io.IOException: too many concurrent streams
    at java.base/java.util.concurrent.CompletableFuture.encodeRelay(CompletableFuture.java:367) ~[?:?]
    at java.base/java.util.concurrent.CompletableFuture.uniComposeStage(CompletableFuture.java:1108) ~[?:?]
    at java.base/java.util.concurrent.CompletableFuture.thenCompose(CompletableFuture.java:2235) ~[?:?]
    at java.net.http/jdk.internal.net.http.MultiExchange.responseAsyncImpl(MultiExchange.java:345) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.MultiExchange.lambda$responseAsync0$2(MultiExchange.java:250) ~[java.net.http:?]
    at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1072) ~[?:?]
    at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506) ~[?:?]
    at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1705) ~[?:?]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
    at java.base/java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: java.io.IOException: too many concurrent streams
    at java.net.http/jdk.internal.net.http.Http2Connection.reserveStream(Http2Connection.java:440) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.Http2ClientImpl.getConnectionFor(Http2ClientImpl.java:103) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.ExchangeImpl.get(ExchangeImpl.java:88) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.Exchange.establishExchange(Exchange.java:293) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.Exchange.responseAsyncImpl0(Exchange.java:425) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.Exchange.responseAsyncImpl(Exchange.java:330) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.Exchange.responseAsync(Exchange.java:322) ~[java.net.http:?]
    at java.net.http/jdk.internal.net.http.MultiExchange.responseAsyncImpl(MultiExchange.java:304) ~[java.net.http:?]

有人可以帮助我解决此问题吗？

该服务器为Tomcat9，默认为最大并发流。

Answer 1

当我尝试连续打服务器时

服务器具有max_concurrent_streams的设置，该设置在初始建立HTTP / 2连接期间会与客户端通信。

如果您使用sendAsync盲目“连续命中服务器”，则不是在等待先前的请求完成，最终您超过了max_concurrent_streams的值，并收到上述错误。

解决方案是同时发送数量少于max_concurrent_streams的请求；之后，您只有在前一个请求完成后才发送新请求。可以使用Semaphore或类似方法在客户端上轻松实现。

Answer 2

不幸的是，@ sbordet建议使用Semaphore的方法对我不起作用。我尝试过：

var semaphore = semaphores.computeIfAbsent(getRequestKey(request), k -> new Semaphore(MAX_CONCURRENT_REQUESTS_NUMBER));

CompletableFuture.runAsync(semaphore::acquireUninterruptibly, WAITING_POOL)
                .thenComposeAsync(ignored -> httpClient.sendAsync(request, responseBodyHandler), ASYNC_POOL)
                .whenComplete((response, e) -> semaphore.release());

无法保证在执行传递到下一个释放信号量的下一个CompletableFuture时释放连接流。对我来说，这种方法在正常执行的情况下有效，但是，如果有任何异常，似乎在调用semaphore.release()之后可能会关闭连接流。

最后，我最终使用了OkHttp。它解决了这个问题（如果并发流的数量达到max_concurrent_streams，它会等到一些流被释放为止）。它还处理GOAWAY框架。对于Java HttpClient，我必须实现重试逻辑来处理此问题，因为如果服务器发送IOException帧，它将抛出GOAWAY。

Java 11 HttpClient Http2流太多错误

2 个答案: