Enhancement for detection of insufficient threads (#1010)

* Issue #586 Enhancement for detection of insufficient threads

Do not count acceptors and selectors at server level if connector uses own dedicated thread pool

Signed-off-by: vladimir.bukhtoyarov <jsecoder@mail.ru>

jetty-server/src/main/java/org/eclipse/jetty/server/Server.java

@@ -29,6 +29,7 @@ import java.util.Date;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executor;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 
@@ -350,29 +351,39 @@ public class Server extends HandlerWrapper implements Attributes
         }
         
         HttpGenerator.setJettyVersion(HttpConfiguration.SERVER_VERSION);
-        MultiException mex=new MultiException();
+
 
         // check size of thread pool
         SizedThreadPool pool = getBean(SizedThreadPool.class);
         int max=pool==null?-1:pool.getMaxThreads();
         int selectors=0;
         int acceptors=0;
-        if (mex.size()==0)
-        {
+
         for (Connector connector : _connectors)
         {
-                if (connector instanceof AbstractConnector)
-                    acceptors+=((AbstractConnector)connector).getAcceptors();
+            if (!(connector instanceof AbstractConnector))
+                continue;
+
+            AbstractConnector abstractConnector = (AbstractConnector) connector;
+            Executor connectorExecutor = connector.getExecutor();
+
+            if (connectorExecutor != pool)
+                // Do not count the selectors and acceptors from this connector at server level, because connector uses dedicated executor.
+                continue;
+
+            acceptors += abstractConnector.getAcceptors();
 
             if (connector instanceof ServerConnector)
                 selectors+=((ServerConnector)connector).getSelectorManager().getSelectorCount();
+
         }
-        }
+
 
         int needed=1+selectors+acceptors;
         if (max>0 && needed>max)
             throw new IllegalStateException(String.format("Insufficient threads: max=%d < needed(acceptors=%d + selectors=%d + request=1)",max,acceptors,selectors));
 
+        MultiException mex=new MultiException();
         try
         {
             super.doStart();

jetty-server/src/test/java/org/eclipse/jetty/server/InsufficientThreadsDetectionTest.java

@@ -0,0 +1,86 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.server;
+
+import org.eclipse.jetty.util.thread.QueuedThreadPool;
+import org.eclipse.jetty.util.thread.ThreadPool;
+import org.junit.After;
+import org.junit.Test;
+
+public class InsufficientThreadsDetectionTest {
+
+    private Server _server;
+
+    @After
+    public void dispose() throws Exception
+    {
+        _server.stop();
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testConnectorUsesServerExecutorWithNotEnoughThreads() throws Exception
+    {
+        // server has 3 threads in the executor
+        _server = new Server(new QueuedThreadPool(3));
+
+        // connector will use executor from server because connectorPool is null
+        ThreadPool connectorPool = null;
+        // connector requires 7 threads(2 + 4 + 1)
+        ServerConnector connector = new ServerConnector(_server, connectorPool, null, null, 2, 4, new HttpConnectionFactory());
+        connector.setPort(0);
+        _server.addConnector(connector);
+
+        // should throw IllegalStateException because there are no required threads in server pool
+        _server.start();
+    }
+
+    @Test
+    public void testConnectorWithDedicatedExecutor() throws Exception
+    {
+        // server has 3 threads in the executor
+        _server = new Server(new QueuedThreadPool(3));
+
+        // connector pool has 100 threads
+        ThreadPool connectorPool = new QueuedThreadPool(100);
+        // connector requires 7 threads(2 + 4 + 1)
+        ServerConnector connector = new ServerConnector(_server, connectorPool, null, null, 2, 4, new HttpConnectionFactory());
+        connector.setPort(0);
+        _server.addConnector(connector);
+
+        // should not throw exception because connector uses own executor, so its threads should not be counted
+        _server.start();
+    }
+
+    @Test // Github issue #586
+    public void testCaseForMultipleConnectors() throws Exception {
+        // server has 3 threads in the executor
+        _server = new Server(new QueuedThreadPool(3));
+
+        // first connector consumes all 3 threads from server pool
+        _server.addConnector(new ServerConnector(_server, null, null, null, 1, 1, new HttpConnectionFactory()));
+
+        // second connect also require 3 threads but uses own executor, so its threads should not be counted
+        final QueuedThreadPool connectorPool = new QueuedThreadPool(3, 3);
+        _server.addConnector(new ServerConnector(_server, connectorPool, null, null, 1, 1, new HttpConnectionFactory()));
+
+        // should not throw exception because limit was not overflown
+        _server.start();
+    }
+
+}