Spring Boot (auto-)configuration class that defines an additional Tomcat Connector for health checks

TomcatAutoConfiguration.java

import org.apache.catalina.connector.Connector;
import org.apache.coyote.AbstractProtocol;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;

@Configuration
@EnableConfigurationProperties(TomcatAutoConfiguration.HealthConnectorProperties.class)
public class TomcatAutoConfiguration {

    /**
     * Creates an addition {@link Connector} for Tomcat that we use for the health checks.
     * This ensures that even when all the request handling threads from the regular connector
     * are in use, we can still respond to health check requests made on port 8888.
     */
    @Profile("!local")
    @Bean
    WebServerFactoryCustomizer<TomcatServletWebServerFactory> tomcatHealthConnectorCustomizer(TomcatAutoConfiguration.HealthConnectorProperties connector) {
        return server -> {
            Connector healthConnector = new Connector();
            healthConnector.setPort(connector.getPort());
            AbstractProtocol protocol = (AbstractProtocol) healthConnector.getProtocolHandler();
            protocol.setMinSpareThreads(connector.getMinThreads());
            protocol.setMaxThreads(connector.getMaxThreads());
            server.addAdditionalTomcatConnectors(healthConnector);
        };
    }


    @ConfigurationProperties("health.connector")
    public static class HealthConnectorProperties {
        /** port number used by the addition Tomcat connector for health checks */
        private int port = 8888;
        private int minThreads = 1;
        private int maxThreads = 5;

        public int getPort() {
            return port;
        }

        public void setPort(int port) {
            this.port = port;
        }

        public int getMinThreads() {
            return minThreads;
        }

        public void setMinThreads(int minThreads) {
            this.minThreads = minThreads;
        }

        public int getMaxThreads() {
            return maxThreads;
        }

        public void setMaxThreads(int maxThreads) {
            this.maxThreads = maxThreads;
        }
    }

}