Fixes #2828 - AbstractHTTP2ServerConnectionFactory concurrent connect low performance.

Now HTTP/2 sessions are not added to the Jetty component tree,
but rather just held by HTTP2SessionContainer that is added to
the Jetty container tree at startup.

HTTP2SessionContainer uses a concurrent Set to hold HTTP/2 sessions
to have good add/remove performance.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>

jetty-http2/http2-server/src/main/java/org/eclipse/jetty/http2/server/AbstractHTTP2ServerConnectionFactory.java

@@ -18,13 +18,17 @@
 
 package org.eclipse.jetty.http2.server;
 
+import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.eclipse.jetty.http2.BufferingFlowControlStrategy;
 import org.eclipse.jetty.http2.FlowControlStrategy;
 import org.eclipse.jetty.http2.HTTP2Connection;
+import org.eclipse.jetty.http2.api.Session;
 import org.eclipse.jetty.http2.api.server.ServerSessionListener;
 import org.eclipse.jetty.http2.frames.Frame;
 import org.eclipse.jetty.http2.frames.SettingsFrame;
@@ -38,12 +42,14 @@ import org.eclipse.jetty.server.HttpConfiguration;
 import org.eclipse.jetty.util.annotation.ManagedAttribute;
 import org.eclipse.jetty.util.annotation.ManagedObject;
 import org.eclipse.jetty.util.annotation.Name;
+import org.eclipse.jetty.util.component.ContainerLifeCycle;
+import org.eclipse.jetty.util.component.Dumpable;
 import org.eclipse.jetty.util.component.LifeCycle;
 
 @ManagedObject
 public abstract class AbstractHTTP2ServerConnectionFactory extends AbstractConnectionFactory
 {
-    private final Connection.Listener connectionListener = new ConnectionListener();
+    private final HTTP2SessionContainer sessionContainer = new HTTP2SessionContainer();
     private final HttpConfiguration httpConfiguration;
     private int maxDynamicTableSize = 4096;
     private int initialSessionRecvWindow = 1024 * 1024;
@@ -66,6 +72,7 @@ public abstract class AbstractHTTP2ServerConnectionFactory extends AbstractConne
         for (String p:protocols)
             if (!HTTP2ServerConnection.isSupportedProtocol(p))
                 throw new IllegalArgumentException("Unsupported HTTP2 Protocol variant: "+p);
+        addBean(sessionContainer);
         this.httpConfiguration = Objects.requireNonNull(httpConfiguration);
         addBean(httpConfiguration);
         setInputBufferSize(Frame.DEFAULT_MAX_LENGTH + Frame.HEADER_LENGTH);
@@ -234,7 +241,7 @@ public abstract class AbstractHTTP2ServerConnectionFactory extends AbstractConne
 
         HTTP2Connection connection = new HTTP2ServerConnection(connector.getByteBufferPool(), connector.getExecutor(),
                         endPoint, httpConfiguration, parser, session, getInputBufferSize(), listener);
-        connection.addListener(connectionListener);
+        connection.addListener(sessionContainer);
         return configure(connection, connector, endPoint);
     }
 
@@ -245,18 +252,43 @@ public abstract class AbstractHTTP2ServerConnectionFactory extends AbstractConne
         return new ServerParser(connector.getByteBufferPool(), listener, getMaxDynamicTableSize(), getHttpConfiguration().getRequestHeaderSize());
     }
 
-    private class ConnectionListener implements Connection.Listener
+    private class HTTP2SessionContainer implements Connection.Listener, Dumpable
     {
+        private final Set<Session> sessions = ConcurrentHashMap.newKeySet();
+
         @Override
         public void onOpened(Connection connection)
         {
-            addManaged((LifeCycle)((HTTP2Connection)connection).getSession());
+            Session session = ((HTTP2Connection)connection).getSession();
+            sessions.add(session);
+            LifeCycle.start(session);
         }
 
         @Override
         public void onClosed(Connection connection)
         {
-            removeBean(((HTTP2Connection)connection).getSession());
+            Session session = ((HTTP2Connection)connection).getSession();
+            if (sessions.remove(session))
+                LifeCycle.stop(session);
+        }
+
+        @Override
+        public String dump()
+        {
+            return ContainerLifeCycle.dump(this);
+        }
+
+        @Override
+        public void dump(Appendable out, String indent) throws IOException
+        {
+            ContainerLifeCycle.dumpObject(out, this);
+            ContainerLifeCycle.dump(out, indent, sessions);
+        }
+
+        @Override
+        public String toString()
+        {
+            return String.format("%s@%x[size=%d]", getClass().getSimpleName(), hashCode(), sessions.size());
         }
     }
 }