HADOOP-15311. HttpServer2 needs a way to configure the acceptor/selector count. Contributed by Erik Krogen

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

@@ -134,6 +134,14 @@ public final class HttpServer2 implements FilterContainer {
       "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_ACCEPTOR_COUNT_KEY =
+      "hadoop.http.acceptor.count";
+  // -1 to use default behavior of setting count based on CPU core count
+  public static final int HTTP_ACCEPTOR_COUNT_DEFAULT = -1;
+  public static final String HTTP_SELECTOR_COUNT_KEY =
+      "hadoop.http.selector.count";
+  // -1 to use default behavior of setting count based on CPU core count
+  public static final int HTTP_SELECTOR_COUNT_DEFAULT = -1;
   public static final String HTTP_TEMP_DIR_KEY = "hadoop.http.temp.dir";
 
   public static final String FILTER_INITIALIZER_PROPERTY
@@ -465,7 +473,9 @@ public final class HttpServer2 implements FilterContainer {
 
     private ServerConnector createHttpChannelConnector(
         Server server, HttpConfiguration httpConfig) {
-      ServerConnector conn = new ServerConnector(server);
+      ServerConnector conn = new ServerConnector(server,
+          conf.getInt(HTTP_ACCEPTOR_COUNT_KEY, HTTP_ACCEPTOR_COUNT_DEFAULT),
+          conf.getInt(HTTP_SELECTOR_COUNT_KEY, HTTP_SELECTOR_COUNT_DEFAULT));
       ConnectionFactory connFactory = new HttpConnectionFactory(httpConfig);
       conn.addConnectionFactory(connFactory);
       configureChannelConnector(conn);

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

@@ -147,7 +147,7 @@ public class TestHttpServer extends HttpServerFunctionalTest {
 
   @BeforeClass public static void setup() throws Exception {
     Configuration conf = new Configuration();
-    conf.setInt(HttpServer2.HTTP_MAX_THREADS_KEY, 10);
+    conf.setInt(HttpServer2.HTTP_MAX_THREADS_KEY, MAX_THREADS);
     server = createTestServer(conf);
     server.addServlet("echo", "/echo", EchoServlet.class);
     server.addServlet("echomap", "/echomap", EchoMapServlet.class);
@@ -195,6 +195,27 @@ public class TestHttpServer extends HttpServerFunctionalTest {
     ready.await();
     start.countDown();
   }
+
+  /**
+   * Test that the number of acceptors and selectors can be configured by
+   * trying to configure more of them than would be allowed based on the
+   * maximum thread count.
+   */
+  @Test
+  public void testAcceptorSelectorConfigurability() throws Exception {
+    Configuration conf = new Configuration();
+    conf.setInt(HttpServer2.HTTP_MAX_THREADS_KEY, MAX_THREADS);
+    conf.setInt(HttpServer2.HTTP_ACCEPTOR_COUNT_KEY, MAX_THREADS - 2);
+    conf.setInt(HttpServer2.HTTP_SELECTOR_COUNT_KEY, MAX_THREADS - 2);
+    HttpServer2 badserver = createTestServer(conf);
+    try {
+      badserver.start();
+      // Should not succeed
+      fail();
+    } catch (IOException ioe) {
+      assertTrue(ioe.getCause() instanceof IllegalStateException);
+    }
+  }
   
   @Test public void testEcho() throws Exception {
     assertEquals("a:b\nc:d\n",