Merge pull request #6571 from herau:master

* pr/6571:
  Polish contribution
  Manage Tomcat queued connections

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

@@ -86,6 +86,7 @@ import org.springframework.util.StringUtils;
  * @author Eddú Meléndez
  * @author Quinten De Swaef
  * @author Venil Noronha
+ * @author Aurélien Leboulanger
  */
 @ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
 public class ServerProperties
@@ -656,6 +657,19 @@ public class ServerProperties
 		 */
 		private Charset uriEncoding;
 
+		/**
+		 * Maximum number of connections that the server will accept and process
+		 * at any given time. Once the limit has been reached, the operating system
+		 * may still accept connections based on the "acceptCount" property.
+		 */
+		private int maxConnections = 0;
+
+		/**
+		 * Maximum queue length for incoming connection requests when all possible
+		 * request processing threads are in use.
+		 */
+		private int acceptCount = 0;
+
 		public int getMaxThreads() {
 			return this.maxThreads;
 		}
@@ -748,6 +762,22 @@ public class ServerProperties
 			this.uriEncoding = uriEncoding;
 		}
 
+		public int getMaxConnections() {
+			return this.maxConnections;
+		}
+
+		public void setMaxConnections(int maxConnections) {
+			this.maxConnections = maxConnections;
+		}
+
+		public int getAcceptCount() {
+			return this.acceptCount;
+		}
+
+		public void setAcceptCount(int acceptCount) {
+			this.acceptCount = acceptCount;
+		}
+
 		void customizeTomcat(ServerProperties serverProperties,
 				TomcatEmbeddedServletContainerFactory factory) {
 			if (getBasedir() != null) {
@@ -782,6 +812,40 @@ public class ServerProperties
 			if (this.redirectContextRoot != null) {
 				customizeRedirectContextRoot(factory, this.redirectContextRoot);
 			}
+			if (this.maxConnections > 0) {
+				customizeMaxConnections(factory);
+			}
+			if (this.acceptCount > 0) {
+				customizeAcceptCount(factory);
+			}
+		}
+
+		private void customizeAcceptCount(TomcatEmbeddedServletContainerFactory factory) {
+			factory.addConnectorCustomizers(new TomcatConnectorCustomizer() {
+
+				@Override
+				public void customize(Connector connector) {
+					ProtocolHandler handler = connector.getProtocolHandler();
+					if (handler instanceof AbstractProtocol) {
+						AbstractProtocol protocol = (AbstractProtocol) handler;
+						protocol.setBacklog(Tomcat.this.acceptCount);
+					}
+				}
+			});
+		}
+
+		private void customizeMaxConnections(TomcatEmbeddedServletContainerFactory factory) {
+			factory.addConnectorCustomizers(new TomcatConnectorCustomizer() {
+
+				@Override
+				public void customize(Connector connector) {
+					ProtocolHandler handler = connector.getProtocolHandler();
+					if (handler instanceof AbstractProtocol) {
+						AbstractProtocol protocol = (AbstractProtocol) handler;
+						protocol.setMaxConnections(Tomcat.this.maxConnections);
+					}
+				}
+			});
 		}
 
 		private void customizeConnectionTimeout(

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

@@ -32,6 +32,7 @@ import javax.servlet.SessionTrackingMode;
 import org.apache.catalina.Context;
 import org.apache.catalina.Valve;
 import org.apache.catalina.valves.RemoteIpValve;
+import org.apache.coyote.AbstractProtocol;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
@@ -435,6 +436,34 @@ public class ServerPropertiesTests {
 		assertThat(remoteIpValve.getInternalProxies()).isEqualTo("192.168.0.1");
 	}
 
+	@Test
+	public void customTomcatAcceptCount() {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.tomcat.accept-count", "10");
+		bindProperties(map);
+
+		TomcatEmbeddedServletContainerFactory container = new TomcatEmbeddedServletContainerFactory();
+		this.properties.customize(container);
+		TomcatEmbeddedServletContainer  embeddedContainer =
+				(TomcatEmbeddedServletContainer) container.getEmbeddedServletContainer();
+		assertThat(((AbstractProtocol) embeddedContainer.getTomcat().getConnector()
+				.getProtocolHandler()).getBacklog()).isEqualTo(10);
+	}
+
+	@Test
+	public void customTomcatMaxConnections() {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.tomcat.max-connections", "5");
+		bindProperties(map);
+
+		TomcatEmbeddedServletContainerFactory container = new TomcatEmbeddedServletContainerFactory();
+		this.properties.customize(container);
+		TomcatEmbeddedServletContainer  embeddedContainer =
+				(TomcatEmbeddedServletContainer) container.getEmbeddedServletContainer();
+		assertThat(((AbstractProtocol) embeddedContainer.getTomcat().getConnector()
+				.getProtocolHandler()).getMaxConnections()).isEqualTo(5);
+	}
+
 	@Test
 	public void defaultUseForwardHeadersUndertow() throws Exception {
 		UndertowEmbeddedServletContainerFactory container = spy(

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

@@ -193,6 +193,7 @@ content into your application; rather pick only the properties that you need.
 	server.ssl.trust-store-password= # Password used to access the trust store.
 	server.ssl.trust-store-provider= # Provider for the trust store.
 	server.ssl.trust-store-type= # Type of the trust store.
+	server.tomcat.accept-count= # Maximum queue length for incoming connection requests when all possible request processing threads are in use.
 	server.tomcat.accesslog.directory=logs # Directory in which log files are created. Can be relative to the tomcat base dir or absolute.
 	server.tomcat.accesslog.enabled=false # Enable access log.
 	server.tomcat.accesslog.pattern=common # Format pattern for access logs.
@@ -208,6 +209,7 @@ content into your application; rather pick only the properties that you need.
 			172\\.1[6-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
 			172\\.2[0-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
 			172\\.3[0-1]{1}\\.\\d{1,3}\\.\\d{1,3} # regular expression matching trusted IP addresses.
+	server.tomcat.max-connections= # Maximum number of connections that the server will accept and process at any given time.
 	server.tomcat.max-threads=0 # Maximum amount of worker threads.
 	server.tomcat.min-spare-threads=0 # Minimum amount of worker threads.
 	server.tomcat.port-header=X-Forwarded-Port # Name of the HTTP header used to override the original port value.