Expose Jetty JMX extensions

Jetty by default provides set of MBeans that can be registered in JMX.
This patch adds new configuration option called httpd.registerMBeans, by
default set to false, to control this behavior.

Change-Id: I3771ed3bb755240d7d90e9f1f1d7e7f84ff33ce3
Signed-off-by: Dariusz Luksza <dariusz@luksza.org>

gerrit-pgm/BUCK

@@ -115,6 +115,7 @@ java_library2(
     '//lib/guice:guice-servlet',
     '//lib/jetty:server',
     '//lib/jetty:servlet',
+    '//lib/jetty:jmx',
     '//lib/jgit:jgit',
     '//lib/log:api',
     '//lib/log:log4j',

gerrit-pgm/src/main/java/com/google/gerrit/pgm/http/jetty/JettyServer.java

@@ -39,6 +39,7 @@ import com.google.inject.servlet.GuiceFilter;
 import com.google.inject.servlet.GuiceServletContextListener;
 
 import org.eclipse.jetty.http.HttpScheme;
+import org.eclipse.jetty.jmx.MBeanContainer;
 import org.eclipse.jetty.server.Connector;
 import org.eclipse.jetty.server.ForwardedRequestCustomizer;
 import org.eclipse.jetty.server.Handler;
@@ -58,6 +59,7 @@ import org.eclipse.jetty.servlet.FilterHolder;
 import org.eclipse.jetty.servlet.ServletContextHandler;
 import org.eclipse.jetty.servlet.ServletHolder;
 import org.eclipse.jetty.util.BlockingArrayQueue;
+import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.resource.Resource;
 import org.eclipse.jetty.util.ssl.SslContextFactory;
 import org.eclipse.jetty.util.thread.QueuedThreadPool;
@@ -75,6 +77,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.InterruptedIOException;
 import java.io.PrintWriter;
+import java.lang.management.ManagementFactory;
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -171,6 +174,13 @@ public class JettyServer {
       handler.setHandler(app);
       app = handler;
     }
+    if (cfg.getBoolean("httpd", "registerMBeans", false)) {
+      MBeanContainer mbean =
+          new MBeanContainer(ManagementFactory.getPlatformMBeanServer());
+      httpd.addEventListener(mbean);
+      httpd.addBean(Log.getRootLogger());
+      httpd.addBean(mbean);
+    }
 
     httpd.setHandler(app);
     httpd.setStopAtShutdown(false);