Fixes #558 - HTTP/2 server hangs when thread pool is low on threads.

Fixed test that was broken after changes for #557.

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

@@ -37,7 +37,9 @@ import org.eclipse.jetty.util.thread.ExecutionStrategy;
 import org.eclipse.jetty.util.thread.QueuedThreadPool;
 import org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume;
 import org.eclipse.jetty.util.thread.strategy.ProduceExecuteConsume;
-import org.junit.*;
+import org.junit.After;
+import org.junit.Rule;
+import org.junit.Test;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.junit.Assert.assertEquals;
@@ -165,34 +167,37 @@ public class ThreadStarvationTest
     }
 
     @Test
-    @Ignore
     public void testEPCExitsLowThreadsMode() throws Exception
     {
         prepareServer(new ReadHandler());
-        Assert.assertEquals(2, _availableThreads);
+        _threadPool.setMaxThreads(5);
         _connector.setExecutionStrategyFactory(new ExecuteProduceConsume.Factory());
         _server.start();
         System.err.println(_server.dump());
 
-        // Two idle threads in the pool here.
+        // Three idle threads in the pool here.
         // The server will accept the socket in normal mode.
         Socket client = new Socket("localhost", _connector.getLocalPort());
         client.setSoTimeout(10000);
 
         Thread.sleep(500);
 
-        // Now steal one thread.
+        // Now steal two threads.
-        CountDownLatch latch = new CountDownLatch(1);
+        CountDownLatch[] latches = new CountDownLatch[2];
-        _threadPool.execute(() ->
+        for (int i = 0; i < latches.length; ++i)
         {
-            try
+            CountDownLatch latch = latches[i] = new CountDownLatch(1);
+            _threadPool.execute(() ->
             {
-                latch.await();
+                try
-            }
+                {
-            catch (InterruptedException ignored)
+                    latch.await();
-            {
+                }
-            }
+                catch (InterruptedException ignored)
-        });
+                {
+                }
+            });
+        }
 
         InputStream is = client.getInputStream();
         OutputStream os = client.getOutputStream();
@@ -218,56 +223,25 @@ public class ThreadStarvationTest
             assertTrue(executionStrategy.isLowOnThreads());
         }
 
-        // Release the stolen thread.
+        // Release the stolen threads.
-        latch.countDown();
+        for (CountDownLatch latch : latches)
+            latch.countDown();
         Thread.sleep(500);
 
         // Send the rest of the body to unblock the reader thread.
         // This will be run directly by the selector thread,
-        // which therefore will remain in low threads mode.
+        // which then will exit the low threads mode.
         os.write("234567890".getBytes(StandardCharsets.UTF_8));
         os.flush();
 
         Thread.sleep(500);
         System.err.println(_threadPool.dump());
 
-        // Back to two idle threads here, but we are still in
-        // low threads mode because the SelectorProducer has
-        // not returned from the low threads mode.
-
-        String response = IO.toString(is);
-        assertThat(response, containsString("200 OK"));
-        assertThat(response, containsString("Read Input 10"));
-
-        // Send another request.
-        // Accepting a new connection will exit the low threads mode.
-        client = new Socket("localhost", _connector.getLocalPort());
-        client.setSoTimeout(10000);
-
-        Thread.sleep(500);
-        System.err.println(_threadPool.dump());
-
         for (ManagedSelector selector : _connector.getSelectorManager().getBeans(ManagedSelector.class))
         {
             ExecuteProduceConsume executionStrategy = (ExecuteProduceConsume)selector.getExecutionStrategy();
             assertFalse(executionStrategy.isLowOnThreads());
         }
-
-        is = client.getInputStream();
-        os = client.getOutputStream();
-        request = "" +
-                "PUT / HTTP/1.0\r\n" +
-                "Host: localhost\r\n" +
-                "Content-Length: 10\r\n" +
-                "\r\n" +
-                "1234567890";
-
-        os.write(request.getBytes(StandardCharsets.UTF_8));
-        os.flush();
-
-        response = IO.toString(is);
-        assertThat(response, containsString("200 OK"));
-        assertThat(response, containsString("Read Input 10"));
     }
 
     protected static class ReadHandler extends AbstractHandler