ParallelConnectionsTest.java

/*
 * Copyright 2020 Matthias Bläsing.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.mitre.dsmiley.httpproxy;


import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.ServerConnector;
import org.eclipse.jetty.ee10.servlet.ServletContextHandler;
import org.eclipse.jetty.ee10.servlet.ServletHolder;
import org.junit.After;
import static org.junit.Assert.assertEquals;
import org.junit.Before;
import org.junit.Test;

public class ParallelConnectionsTest {

  private Server server;
  private ServletContextHandler context;
  private int serverPort;

  @Before
  public void setUp() throws Exception {
    server = new Server(0);
    context = new ServletContextHandler();
    context.setContextPath("/");
    server.setHandler(context);
    server.start();

    serverPort = ((ServerConnector) server.getConnectors()[0]).getLocalPort();
  }

  @After
  public void tearDown() throws Exception {
    server.stop();
    serverPort = -1;
  }

  @Test
  public void testHandlingMultipleConnectionsSameRoute() throws Exception {
    /*
     This test ensures, that a minimum nunmber of parallel connections can be
     established. The test works by opening "parallelConnectionsToTest"
     connections, this is enforced by a countdownlatch, that ensures, that all
     connections to the backend are established before they are served by the
     demo servlet.
     */

    int parallelConnectionsToTest = 10;

    ServletHolder servletHolder = context.addServlet(ProxyServlet.class, "/sampleBackendProxied/*");
    servletHolder.setInitParameter(ProxyServlet.P_LOG, "true");
    servletHolder.setInitParameter(ProxyServlet.P_MAXCONNECTIONS, Integer.toString(parallelConnectionsToTest));
    servletHolder.setInitParameter(ProxyServlet.P_TARGET_URI, String.format("http://localhost:%d/sampleBackend/", serverPort));

    CountDownLatch requestsReceived = new CountDownLatch(parallelConnectionsToTest);

    ServletHolder dummyBackend = new ServletHolder(new HttpServlet() {
      @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try {
          // The latch ensures, that all servlets wait until all expected
          // connections are made. Only after all clients have connected, the
          // request is fullfilled.
          requestsReceived.countDown();
          if (requestsReceived.await(10, TimeUnit.SECONDS)) {
            resp.setHeader("Content-Type", "text/plain; charset=utf-8");
            OutputStream os = resp.getOutputStream();
            OutputStreamWriter osw = new OutputStreamWriter(os, StandardCharsets.UTF_8);
            osw.write("Works");
            osw.flush();
          }
        } catch (InterruptedException ex) {
          throw new IOException(ex);
        }
      }
    });
    context.addServlet(dummyBackend, "/sampleBackend/*");

    URL url = new URL(String.format("http://localhost:%d/sampleBackendProxied/test", serverPort));

    ExecutorService es = Executors.newFixedThreadPool(parallelConnectionsToTest);

    class Client implements Callable<String> {
      @Override
      public String call() throws Exception {
        try (InputStream is = url.openStream();
                ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
          byte[] buffer = new byte[10 * 1024];
          int read;
          while((read = is.read(buffer)) > 0) {
            baos.write(buffer, 0, read);
          }
          return baos.toString("UTF-8");
        }
      }
    }

    List<Future<String>> result = new ArrayList<>(parallelConnectionsToTest);

    for(int i = 0; i < parallelConnectionsToTest; i++) {
      result.add(es.submit(new Client()));
    }

    for(Future<String> f: result) {
      assertEquals("Works", f.get());
    }
  }
}