为什么野生蝇服务器不能在建立httpSession之后处理并发REST请求

Question

我遇到了一个我想要理解的难题。我实现了一个非常简单的示例REST服务，它运行在Wildfly服务器中。我有一个独立的多线程Java测试程序，它使用Apache http客户端库来访问服务。客户端程序有两个独立的线程，同时访问REST服务。在没有在服务器上建立httpSession的情况下运行测试程序时，服务器将并发处理请求(如服务器日志中所示)。如果线程是在建立httpSession之后运行的，则请求由服务器以顺序的方式处理(如第二个服务器日志所示)。请注意，两个线程共享一个会话。

这是故意的吗？我在这里错过了什么？提前谢谢。

以下是我所处环境的基本要素：

• Wildfly Server Info: Wildfly-17.0.0.使用独立的、高可用性的配置在Windows 10上最后运行-ha.xml
• Client Info: ApacheHTTPClient4.5.5(托管版本)。

这里是表示这两种情况的服务器日志：

Server log when no http session is established.  
Requests run concurrently when there is no session.

13:39:13,384 INFO  (default task-5) Getting widget 3  
13:39:13,384 INFO  (default task-6) Getting widget 4  
13:39:13,384 INFO  (default task-6) DELAYING widget 4  
13:39:13,384 INFO  (default task-5) Returning widget 3  
13:39:13,404 INFO  (default task-6) DELAY COMPLETE widget 4  
13:39:13,404 INFO  (default task-6) Returning widget 4  
13:39:13,408 INFO  (default task-6) Getting widget 3  
13:39:13,408 INFO  (default task-6) Returning widget 3  
13:39:13,409 INFO  (default task-5) Getting widget 4  
13:39:13,409 INFO  (default task-5) DELAYING widget 4  
13:39:13,413 INFO  (default task-6) Getting widget 3  
13:39:13,413 INFO  (default task-6) Returning widget 3  
13:39:13,419 INFO  (default task-6) Getting widget 3  
13:39:13,419 INFO  (default task-6) Returning widget 3  
13:39:13,425 INFO  (default task-6) Getting widget 3  
13:39:13,425 INFO  (default task-6) Returning widget 3  
13:39:13,430 INFO  (default task-6) Getting widget 3  
13:39:13,430 INFO  (default task-6) Returning widget 3  
13:39:13,436 INFO  (default task-5) DELAY COMPLETE widget 4  
13:39:13,436 INFO  (default task-5) Returning widget 4  
13:39:13,436 INFO  (default task-6) Getting widget 3  
13:39:13,436 INFO  (default task-6) Returning widget 3  
13:39:13,441 INFO  (default task-6) Getting widget 4  
13:39:13,441 INFO  (default task-5) Getting widget 3  
13:39:13,442 INFO  (default task-6) DELAYING widget 4  
13:39:13,442 INFO  (default task-5) Returning widget 3  
13:39:13,447 INFO  (default task-5) Getting widget 3  
13:39:13,447 INFO  (default task-5) Returning widget 3  
...

Server log after having established a http session.  
Requests run sequentially after having established a session.

13:41:08,761 INFO  (default task-5) Session established PA7xR3HCYMR3A2S6iX-4Ziw1dGVNejPktseYMMdm  
13:41:08,808 INFO  (default task-5) Getting widget 4  
13:41:08,808 INFO  (default task-5) DELAYING widget 4  
13:41:08,829 INFO  (default task-5) DELAY COMPLETE widget 4  
13:41:08,829 INFO  (default task-5) Returning widget 4  
13:41:08,833 INFO  (default task-6) Getting widget 3  
13:41:08,833 INFO  (default task-6) Returning widget 3  
13:41:08,837 INFO  (default task-5) Getting widget 4  
13:41:08,837 INFO  (default task-5) DELAYING widget 4  
13:41:08,857 INFO  (default task-5) DELAY COMPLETE widget 4  
13:41:08,857 INFO  (default task-5) Returning widget 4  
13:41:08,860 INFO  (default task-6) Getting widget 3  
13:41:08,860 INFO  (default task-6) Returning widget 3  
13:41:08,863 INFO  (default task-5) Getting widget 4  
13:41:08,864 INFO  (default task-5) DELAYING widget 4  
13:41:08,884 INFO  (default task-5) DELAY COMPLETE widget 4  
13:41:08,884 INFO  (default task-5) Returning widget 4  
13:41:08,887 INFO  (default task-6) Getting widget 3  
13:41:08,887 INFO  (default task-6) Returning widget 3  
13:41:08,890 INFO  (default task-5) Getting widget 4  
13:41:08,890 INFO  (default task-5) DELAYING widget 4  
13:41:08,911 INFO  (default task-5) DELAY COMPLETE widget 4  
13:41:08,911 INFO  (default task-5) Returning widget 4  
13:41:08,914 INFO  (default task-6) Getting widget 3  
13:41:08,915 INFO  (default task-6) Returning widget 3  
...  

这是REST服务实现

@Path("concurrencyTest")
@Stateless
public class ConcurrencyTestWs extends BaseWs {
  private static final Logger log = LoggerFactory
      .getLogger(ConcurrencyTestWs.class);

  @SuppressWarnings("static-method")
  @GET
  @Path("/widget")
  public Response getWidget(@Context HttpServletRequest request,
      @QueryParam(value = "widgetId") Long widgetId) {
    try {
      log.info(String.format("Getting widget %d", widgetId));
      if ((widgetId % 2) == 0) {
        log.info(String.format("DELAYING widget %d", widgetId));
        try {
          Thread.sleep(20);
        } catch (Exception e) {
          System.err.println(e.getMessage());
        }
        log.info(String.format("DELAY COMPLETE widget %d", widgetId));
      }
      log.info(String.format("Returning widget %d", widgetId));
      return Response.ok(String.format("Widget %d retrieved", widgetId))
          .build();
    } catch (Exception e) {
      return RestUtilities.getInternalError(request, "Widget", widgetId, e);
    }
  }

  @SuppressWarnings("static-method")
  @POST
  @Path("/establishSession")
  public Response establishSession(@Context HttpServletRequest request) {
    try {
      HttpSession session = request.getSession(true);
      log.info(String.format("Session established %s", session.getId()));
      Response response = Response.ok().build();
      return response;
    } catch (Exception e) {
      return RestUtilities.getInternalError(request, e);
    }
  }

  @SuppressWarnings("static-method")
  @POST
  @Path("/terminateSession")
  public Response terminateSession(@Context HttpServletRequest request) {
    try {
      HttpSession session = request.getSession(false);
      log.info(String.format("Terminating session %s",
          (session == null) ? "null" : session.getId()));
      Response response = Response.ok().build();
      return response;
    } catch (Exception e) {
      return RestUtilities.getInternalError(request, e);
    }
  }

}

这里是客户端源代码

public class WidgetFetchTest {

  private final static String restServiceUrl = "http://dtp002.novodynamics.com:8081/TEST/REST/v1.0/concurrencyTest";
  private final CloseableHttpClient httpClient;
  private final CookieStore cookieStore;

  public WidgetFetchTest() {
    this.cookieStore = new BasicCookieStore();

    RequestConfig requestConfig = RequestConfig.custom()
        .setConnectTimeout(60000).setConnectionRequestTimeout(60000)
        .setSocketTimeout(60000).setCookieSpec(CookieSpecs.STANDARD).build();

    @SuppressWarnings("resource")
    PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
    connectionManager.setMaxTotal(100);
    connectionManager.setDefaultMaxPerRoute(40);

    this.httpClient = HttpClients.custom()
        .setDefaultRequestConfig(requestConfig)
        .setDefaultCookieStore(this.cookieStore)
        .setConnectionManager(connectionManager).build();
  }

  public void run() {
    establishSession(this.httpClient);
    DocFetchRunnable r1 = new DocFetchRunnable("4", this.httpClient);
    DocFetchRunnable r2 = new DocFetchRunnable("3", this.httpClient);
    ExecutorService exec = Executors.newFixedThreadPool(2);
    exec.execute(r1);
    exec.execute(r2);
    try {
      Thread.sleep(60000);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }

  }

  protected static void establishSession(CloseableHttpClient client) {
    try {
      URIBuilder ub = new URIBuilder(
          String.format("%s%s", restServiceUrl, "/establishSession"));
      String url = ub.toString();
      HttpContext ctx = HttpClientContext.create();
      try (CloseableHttpResponse response = client.execute(new HttpPost(url),
          ctx)) {
        // intentionally empty.
      } catch (Exception e) {
        e.printStackTrace();
      }
    } catch (URISyntaxException e) {
      e.printStackTrace();
    }
  }

  protected static void getWidget(CloseableHttpClient client, String widgetId) {
    try {
      URIBuilder ub = new URIBuilder(
          String.format("%s%s", restServiceUrl, "/widget"));
      ub.addParameter("widgetId", widgetId);
      String url = ub.toString();
      HttpContext ctx = HttpClientContext.create();
      try (CloseableHttpResponse response = client.execute(new HttpGet(url),
          ctx)) {
        // intentionally empty.
      } catch (Exception e) {
        e.printStackTrace();
      }
    } catch (URISyntaxException e) {
      e.printStackTrace();
    }
  }

  private class DocFetchRunnable implements Runnable {
    private String widgetId;
    CloseableHttpClient client;

    public DocFetchRunnable(String widgetId, CloseableHttpClient client) {
      this.widgetId = widgetId;
      this.client = client;
    }

    @Override
    public void run() {
      for (int i = 0; i < 50; i++) {
        System.out.println(
            String.format("Fetching widget %s - %d", this.widgetId, i));
        System.out.flush();
        getWidget(this.client, this.widgetId);
        System.out.println(
            String.format("Widget fetched  %s - %d", this.widgetId, i));
        System.out.flush();
      }
    }
  }

  public static void main(String[] args) {
    WidgetFetchTest dft = new WidgetFetchTest();
    dft.run();
    System.exit(0);
  }
}

Answer 1

在JBossDeveloper论坛上发布这个问题后，提供了以下答案。

请参阅文档：可分发的Web应用程序，会话并发中关于会话并发的部分。

通过在关联的缓存配置上放松从REPEATABLE_READ到READ_COMMITTED的隔离，可以解决此问题。