Add more debug logging to smoke test async servlet (open-telemetry#8720)

Author: laurit

smoke-tests/images/servlet/servlet-3.0/src/main/java/io/opentelemetry/smoketest/matrix/AsyncGreetingServlet.java

@@ -57,6 +57,13 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
 
   private static void handleRequest(AsyncContext ac) {
     System.err.println("dispatch async request");
-    ac.dispatch("/greeting");
+    try {
+      ac.dispatch("/greeting");
+      System.err.println("async request dispatched");
+    } catch (Throwable throwable) {
+      System.err.println("dispatching async request failed");
+      throwable.printStackTrace();
+      throw throwable;
+    }
   }
 }

smoke-tests/images/servlet/servlet-3.0/src/main/java/io/opentelemetry/smoketest/matrix/GreetingServlet.java

@@ -17,11 +17,13 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+@SuppressWarnings("SystemOut")
 public class GreetingServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;
 
   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    System.err.println("called GreetingServlet doGet");
     String path = (req.getContextPath() + "/headers").replace("//", "/");
     URL url = new URL("http", "localhost", req.getLocalPort(), path);
     URLConnection urlConnection = url.openConnection();
@@ -34,6 +36,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IO
           bytesRead + " bytes read by " + urlConnection.getClass().getName() + "\n" + responseBody);
       outputStream.flush();
     }
+    System.err.println("GreetingServlet doGet completed");
   }
 
   // We have to run on Java 8, so no Java 9 stream transfer goodies for us.

smoke-tests/images/servlet/servlet-5.0/src/main/java/io/opentelemetry/smoketest/matrix/AsyncGreetingServlet.java

@@ -56,6 +56,13 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
 
   private static void handleRequest(AsyncContext ac) {
     System.err.println("dispatch async request");
-    ac.dispatch("/greeting");
+    try {
+      ac.dispatch("/greeting");
+      System.err.println("async request dispatched");
+    } catch (Throwable throwable) {
+      System.err.println("dispatching async request failed");
+      throwable.printStackTrace();
+      throw throwable;
+    }
   }
 }

smoke-tests/images/servlet/servlet-5.0/src/main/java/io/opentelemetry/smoketest/matrix/GreetingServlet.java

@@ -17,11 +17,13 @@
 import java.net.URLConnection;
 import java.util.Objects;
 
+@SuppressWarnings("SystemOut")
 public class GreetingServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;
 
   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    System.err.println("called GreetingServlet doGet");
     String path = (req.getContextPath() + "/headers").replace("//", "/");
     URL url = new URL("http", "localhost", req.getLocalPort(), path);
     URLConnection urlConnection = url.openConnection();
@@ -34,6 +36,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IO
           bytesRead + " bytes read by " + urlConnection.getClass().getName() + "\n" + responseBody);
       outputStream.flush();
     }
+    System.err.println("GreetingServlet doGet completed");
   }
 
   // We have to run on Java 8, so no Java 9 stream transfer goodies for us.