HADOOP-14560. Make HttpServer2 backlog size configurable. Contributed by Alexander Krasheninnikov.

This closes #242.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/HttpServer2.java

@@ -128,6 +128,10 @@ public final class HttpServer2 implements FilterContainer {
   public static final String HTTP_MAX_RESPONSE_HEADER_SIZE_KEY =
       "hadoop.http.max.response.header.size";
   public static final int HTTP_MAX_RESPONSE_HEADER_SIZE_DEFAULT = 65536;
+
+  public static final String HTTP_SOCKET_BACKLOG_SIZE_KEY =
+      "hadoop.http.socket.backlog.size";
+  public static final int HTTP_SOCKET_BACKLOG_SIZE_DEFAULT = 128;
   public static final String HTTP_MAX_THREADS_KEY = "hadoop.http.max.threads";
   public static final String HTTP_TEMP_DIR_KEY = "hadoop.http.temp.dir";
 
@@ -433,6 +437,9 @@ public final class HttpServer2 implements FilterContainer {
       httpConfig.setResponseHeaderSize(responseHeaderSize);
       httpConfig.setSendServerVersion(false);
 
+      int backlogSize = conf.getInt(HTTP_SOCKET_BACKLOG_SIZE_KEY,
+          HTTP_SOCKET_BACKLOG_SIZE_DEFAULT);
+
       for (URI ep : endpoints) {
         final ServerConnector connector;
         String scheme = ep.getScheme();
@@ -448,6 +455,7 @@ public final class HttpServer2 implements FilterContainer {
         }
         connector.setHost(ep.getHost());
         connector.setPort(ep.getPort() == -1 ? 0 : ep.getPort());
+        connector.setAcceptQueueSize(backlogSize);
         server.addListener(connector);
       }
       server.loadListeners();
@@ -640,7 +648,6 @@ public final class HttpServer2 implements FilterContainer {
 
   private static void configureChannelConnector(ServerConnector c) {
     c.setIdleTimeout(10000);
-    c.setAcceptQueueSize(128);
     if(Shell.WINDOWS) {
       // result of setting the SO_REUSEADDR flag is different on Windows
       // http://msdn.microsoft.com/en-us/library/ms740621(v=vs.85).aspx

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/http/TestHttpServer.java

@@ -682,4 +682,17 @@ public class TestHttpServer extends HttpServerFunctionalTest {
       stopHttpServer(myServer2);
     }
   }
+
+  @Test
+  public void testBacklogSize() throws Exception
+  {
+    final int backlogSize = 2048;
+    Configuration conf = new Configuration();
+    conf.setInt(HttpServer2.HTTP_SOCKET_BACKLOG_SIZE_KEY, backlogSize);
+    HttpServer2 srv = createServer("test", conf);
+    List<?> listeners = (List<?>) Whitebox.getInternalState(srv,
+            "listeners");
+    ServerConnector listener = (ServerConnector)listeners.get(0);
+    assertEquals(backlogSize, listener.getAcceptQueueSize());
+  }
 }