Add configuration property for configuring Tomcat's processor cache

See gh-15054

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

@@ -56,6 +56,7 @@ import org.springframework.util.unit.DataSize;
  * @author Brian Clozel
  * @author Olivier Lamy
  * @author Chentao Qu
+ * @author Artsiom Yudovin
  */
 @ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
 public class ServerProperties {
@@ -369,6 +370,12 @@ public class ServerProperties {
 		 */
 		private int acceptCount = 100;
 
+		/**
+		 * Maximum number of idle processors that will be retained in the cache and reused
+		 * with a subsequent request.
+		 */
+		private int processorCache = 200;
+
 		/**
 		 * Comma-separated list of additional patterns that match jars to ignore for TLD
 		 * scanning. The special '?' and '*' characters can be used in the pattern to
@@ -524,6 +531,14 @@ public class ServerProperties {
 			this.acceptCount = acceptCount;
 		}
 
+		public int getProcessorCache() {
+			return this.processorCache;
+		}
+
+		public void setProcessorCache(int processorCache) {
+			this.processorCache = processorCache;
+		}
+
 		public List<String> getAdditionalTldSkipPatterns() {
 			return this.additionalTldSkipPatterns;
 		}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/embedded/TomcatWebServerFactoryCustomizer.java

@@ -108,6 +108,8 @@ public class TomcatWebServerFactoryCustomizer implements
 				.to((maxConnections) -> customizeMaxConnections(factory, maxConnections));
 		propertyMapper.from(tomcatProperties::getAcceptCount).when(this::isPositive)
 				.to((acceptCount) -> customizeAcceptCount(factory, acceptCount));
+		propertyMapper.from(tomcatProperties::getProcessorCache).when(this::isPositive)
+				.to((processorCache) -> customizeProcessorCache(factory, processorCache));
 		customizeStaticResources(factory);
 		customizeErrorReportValve(properties.getError(), factory);
 	}
@@ -156,6 +158,13 @@ public class TomcatWebServerFactoryCustomizer implements
 		});
 	}
 
+	private void customizeProcessorCache(ConfigurableTomcatWebServerFactory factory,
+			int processorCache) {
+		factory.addConnectorCustomizers((
+				connector) -> ((AbstractHttp11Protocol<?>) connector.getProtocolHandler())
+						.setProcessorCache(processorCache));
+	}
+
 	private void customizeRemoteIpValve(ConfigurableTomcatWebServerFactory factory) {
 		Tomcat tomcatProperties = this.serverProperties.getTomcat();
 		String protocolHeader = tomcatProperties.getProtocolHeader();

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/embedded/TomcatWebServerFactoryCustomizerTests.java

@@ -87,6 +87,12 @@ public class TomcatWebServerFactoryCustomizerTests {
 						.isEqualTo(10));
 	}
 
+	@Test
+	public void customProcessorCache() {
+		bind("server.tomcat.processor-cache=100");
+		assertThat(this.serverProperties.getTomcat().getProcessorCache()).isEqualTo(100);
+	}
+
 	@Test
 	public void customBackgroundProcessorDelay() {
 		bind("server.tomcat.background-processor-delay=5");

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

@@ -276,6 +276,7 @@ content into your application. Rather, pick only the properties that you need.
 	server.tomcat.max-threads=200 # Maximum amount of worker threads.
 	server.tomcat.min-spare-threads=10 # Minimum amount of worker threads.
 	server.tomcat.port-header=X-Forwarded-Port # Name of the HTTP header used to override the original port value.
+	server.tomcat.processor-cache= # Maximum number of idle processors that will be retained in the cache and reused with a subsequent request.
 	server.tomcat.protocol-header= # Header that holds the incoming protocol, usually named "X-Forwarded-Proto".
 	server.tomcat.protocol-header-https-value=https # Value of the protocol header indicating whether the incoming request uses SSL.
 	server.tomcat.redirect-context-root=true # Whether requests to the context root should be redirected by appending a / to the path.