Java 11 HttpClient Http2太多流错误

Question

我正在使用Java 11的HttpClient将请求发布到HTTP2服务器。 HttpClient对象创建为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:?]

有人可以帮我解决这个问题吗？

服务器是Tomcat9，其最大并发流是默认值。

Answer 1

当我尝试连续点击服务器时

服务器具有max_concurrent_streams的设置，该设置在初始建立HTTP / 2连接期间传送给客户端。

如果您使用sendAsync盲目地“连续点击服务器”，您不会等待先前的请求完成，最终您超过max_concurrent_streams值并收到上述错误。

解决方案是同时发送一些小于max_concurrent_streams的请求;之后，您只在前一个请求完成时发送新请求。这可以使用Semaphore或类似的东西在客户端轻松实现。

Answer 2

不幸的是，@ sbordet建议的Semaphore方法对我不起作用。我试过这个：

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());

在将执行传递给下一个发布信号量的CompletableFuture时，无法保证连接流的释放。对我来说，这种方法在正常执行的情况下有效，但是如果有任何例外，似乎在调用semaphore.release()之后可能会关闭连接流。

最后，我最终使用OkHttp。它处理问题（如果并发流的数量达到max_concurrent_streams，它只会等待一些流被释放）。它还处理GOAWAY框架。在Java HttpClient的情况下，我必须实现重试逻辑来处理这个，因为它只是抛出IOException，如果服务器发送GOAWAY帧。