Add Jetty `acceptors` and `selectors` support

Add support for Jetty `acceptors` and `selectors` configuration, either
directly on the `JettyEmbeddedServletContainerFactory` or via
`server.jetty.acceptors`/`server.jetty.selectors` server properties.

Fixes gh-5380
Closes gh-5649

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -402,7 +402,7 @@ public class ServerProperties
 		return this.tomcat;
 	}
 
-	private Jetty getJetty() {
+	public Jetty getJetty() {
 		return this.jetty;
 	}
 
@@ -950,11 +950,43 @@ public class ServerProperties
 
 	}
 
-	private static class Jetty {
+	public static class Jetty {
+
+		/**
+		 * Number of acceptor threads to use.
+		 */
+		private Integer acceptors;
+
+		/**
+		 * Number of selector threads to use.
+		 */
+		private Integer selectors;
+
+		public Integer getAcceptors() {
+			return this.acceptors;
+		}
+
+		public void setAcceptors(Integer acceptors) {
+			this.acceptors = acceptors;
+		}
+
+		public Integer getSelectors() {
+			return this.selectors;
+		}
+
+		public void setSelectors(Integer selectors) {
+			this.selectors = selectors;
+		}
 
 		void customizeJetty(ServerProperties serverProperties,
 				JettyEmbeddedServletContainerFactory factory) {
 			factory.setUseForwardHeaders(serverProperties.getOrDeduceUseForwardHeaders());
+			if (this.acceptors != null) {
+				factory.setAcceptors(this.acceptors);
+			}
+			if (this.selectors != null) {
+				factory.setSelectors(this.selectors);
+			}
 			if (serverProperties.getMaxHttpHeaderSize() > 0) {
 				customizeMaxHttpHeaderSize(factory,
 						serverProperties.getMaxHttpHeaderSize());

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/ServerPropertiesTests.java

@@ -64,6 +64,7 @@ import static org.mockito.Mockito.verify;
  * @author Phillip Webb
  * @author Eddú Meléndez
  * @author Quinten De Swaef
+ * @author Venil Noronha
  */
 public class ServerPropertiesTests {
 
@@ -260,6 +261,30 @@ public class ServerPropertiesTests {
 		assertThat(this.properties.getMaxHttpHeaderSize()).isEqualTo(9999);
 	}
 
+	@Test
+	public void testCustomizePostSize() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.maxHttpPostSize", "9999");
+		bindProperties(map);
+		assertThat(this.properties.getMaxHttpPostSize()).isEqualTo(9999);
+	}
+
+	@Test
+	public void testCustomizeJettyAcceptors() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.jetty.acceptors", "10");
+		bindProperties(map);
+		assertThat(this.properties.getJetty().getAcceptors()).isEqualTo(10);
+	}
+
+	@Test
+	public void testCustomizeJettySelectors() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.jetty.selectors", "10");
+		bindProperties(map);
+		assertThat(this.properties.getJetty().getSelectors()).isEqualTo(10);
+	}
+
 	@Test
 	public void testCustomizeTomcatMinSpareThreads() throws Exception {
 		Map<String, String> map = new HashMap<String, String>();

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -218,6 +218,8 @@ content into your application; rather pick only the properties that you need.
 	server.tomcat.protocol-header-https-value=https # Value of the protocol header that indicates that the incoming request uses SSL.
 	server.tomcat.remote-ip-header= # Name of the http header from which the remote ip is extracted. For instance `X-FORWARDED-FOR`
 	server.tomcat.uri-encoding=UTF-8 # Character encoding to use to decode the URI.
+	server.jetty.acceptors= # Number of acceptor threads to use.
+	server.jetty.selectors= # Number of selector threads to use.
 	server.undertow.accesslog.dir= # Undertow access log directory.
 	server.undertow.accesslog.enabled=false # Enable access log.
 	server.undertow.accesslog.pattern=common # Format pattern for access logs.

spring-boot/src/main/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainerFactory.java

@@ -91,6 +91,7 @@ import org.springframework.util.StringUtils;
  * @author Andrey Hihlovskiy
  * @author Andy Wilkinson
  * @author Eddú Meléndez
+ * @author Venil Noronha
  * @see #setPort(int)
  * @see #setConfigurations(Collection)
  * @see JettyEmbeddedServletContainer
@@ -108,6 +109,16 @@ public class JettyEmbeddedServletContainerFactory
 
 	private boolean useForwardHeaders;
 
+	/**
+	 * The number of acceptor threads to use.
+	 */
+	private int acceptors = -1;
+
+	/**
+	 * The number of selector threads to use.
+	 */
+	private int selectors = -1;
+
 	private List<JettyServerCustomizer> jettyServerCustomizers = new ArrayList<JettyServerCustomizer>();
 
 	private ResourceLoader resourceLoader;
@@ -143,7 +154,7 @@ public class JettyEmbeddedServletContainerFactory
 			ServletContextInitializer... initializers) {
 		JettyEmbeddedWebAppContext context = new JettyEmbeddedWebAppContext();
 		int port = (getPort() >= 0 ? getPort() : 0);
-		Server server = new Server(new InetSocketAddress(getAddress(), port));
+		Server server = createServer(port);
 		configureWebAppContext(context, initializers);
 		server.setHandler(addHandlerWrappers(context));
 		this.logger.info("Server initialized with port: " + port);
@@ -163,6 +174,21 @@ public class JettyEmbeddedServletContainerFactory
 		return getJettyEmbeddedServletContainer(server);
 	}
 
+	private Server createServer(int port) {
+		Server server = new Server();
+		server.setConnectors(new Connector[] { createConnector(port, server) });
+		return server;
+	}
+
+	private ServerConnector createConnector(int port, Server server) {
+		ServerConnector connector = new ServerConnector(server, this.acceptors,
+				this.selectors);
+		InetSocketAddress address = new InetSocketAddress(getAddress(), port);
+		connector.setHost(address.getHostName());
+		connector.setPort(address.getPort());
+		return connector;
+	}
+
 	private Handler addHandlerWrappers(Handler handler) {
 		if (getCompression() != null && getCompression().getEnabled()) {
 			handler = applyWrapper(handler, createGzipHandler());
@@ -489,6 +515,24 @@ public class JettyEmbeddedServletContainerFactory
 		this.useForwardHeaders = useForwardHeaders;
 	}
 
+	/**
+	 * Set the number of acceptor threads to use.
+	 * @param acceptors the number of acceptor threads to use
+	 * @since 1.4.0
+	 */
+	public void setAcceptors(int acceptors) {
+		this.acceptors = acceptors;
+	}
+
+	/**
+	 * Set the number of selector threads to use.
+	 * @param selectors the number of selector threads to use
+	 * @since 1.4.0
+	 */
+	public void setSelectors(int selectors) {
+		this.selectors = selectors;
+	}
+
 	/**
 	 * Sets {@link JettyServerCustomizer}s that will be applied to the {@link Server}
 	 * before it is started. Calling this method will replace any existing configurations.