Spring boot + Undertow access log, capture/record request processing time. Customize UndertowWebServerFactory

application.properties

server.undertow.accesslog.pattern=%h %l %u %t "%r" %s %b "%{i,Referer}" "%{i,User-Agent}" %D

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>io.cm</groupId>
  <artifactId>undertow-accesslog</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.1.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <exclusions>
        <exclusion>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-undertow</artifactId>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
    </dependency>
    <dependency>
      <groupId>commons-lang</groupId>
      <artifactId>commons-lang</artifactId>
      <version>2.6</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-devtools</artifactId>
      <scope>runtime</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

UndertowAccessLogApplication.java

package io.cm.accesslog;

import io.undertow.Undertow;
import io.undertow.UndertowOptions;
import io.undertow.server.handlers.accesslog.AccessLogHandler;
import io.undertow.server.handlers.accesslog.AccessLogReceiver;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.StringUtils;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.web.ServerProperties;
import org.springframework.boot.web.embedded.undertow.ConfigurableUndertowWebServerFactory;
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class UndertowAccessLogApplication {

  public static void main(String[] args) {
    SpringApplication.run(UndertowAccessLogApplication.class, args);
  }
}

@RestController
class HelloController {

  @RequestMapping("/")
  public String index() {
    return "Hello world!";
  }
}

@Component
class UndertowWebServerAccessLogTimingEnabler implements WebServerFactoryCustomizer<ConfigurableUndertowWebServerFactory> {

  private final ServerProperties serverProperties;

  public UndertowWebServerAccessLogTimingEnabler(ServerProperties serverProperties) {
    this.serverProperties = serverProperties;
  }

  @Override
  public void customize(ConfigurableUndertowWebServerFactory factory) {
    String pattern = serverProperties.getUndertow().getAccesslog().getPattern();

    // Record request timing only if the pattern
    if (logRequestProcessingTiming(pattern)) {
      factory.addBuilderCustomizers(builder -> builder.setServerOption(UndertowOptions.RECORD_REQUEST_START_TIME, true));
    }

    // Custom access log receiver.
    factory.addDeploymentInfoCustomizers(deploymentInfo -> {
      deploymentInfo.addInitialHandlerChainWrapper(handler -> {
        Slf4jAccessLogReceiver accessLogReceiver = new Slf4jAccessLogReceiver();
        return new AccessLogHandler(handler, accessLogReceiver, pattern, Undertow.class.getClassLoader());
      });
    });
  }

  private boolean logRequestProcessingTiming(String pattern) {
    if (StringUtils.isBlank(pattern)) {
      return false;
    }
    return pattern.contains("%D") || pattern.contains("%T");
  }
}

/**
 * Direct access logs to slf4j. Can be sent to custom location with logger configuration.
 * Default undertow access logs are in the launchDirectory/logs of the process
 */
@Slf4j(topic = "ACCESS_LOG")
class Slf4jAccessLogReceiver implements AccessLogReceiver {

  @Override
  public void logMessage(String message) {
    log.info(message);
  }
}

hey, there is also a property for recording the request start time:
server.undertow.options.server.record-request-start-time=true

Not back when I made this gist. What you see is available in latest SB releases, not in 1.5.X or 2.0.1 releases https://github.com/spring-projects/spring-boot/blob/v2.0.1.RELEASE/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java#L967