Spring Boot : Undertow

Undertow

• Undertow is a NIO-based high-performance Web embedded server developed by Red Hat
• Untertow features:
  • Lightweight: It's a Web server, but unlike traditional Web servers, which have container concept, it consists of two core Jar packages. Loading a Web application can be less than 10MB of memory.
  • Servlet 3.1 support: It provides support for Servlet 3.1
  • WebSocket support: Full support for Web Socket to meet the huge number of clients for Web applications
  • Nesting: It doesn't need containers. It just needs API to build Web servers quickly.
• By default, Spring Cloud uses Tomcat as an embedded Servlet container to start a Tomcat Spring Book program and an Undertow Spring Book program. By comparing with Visual VM tools, we can see that Undertow outperforms Tomcat in performance.

Use Undertow

Add dependency

<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>

Support HTTP2

// Add @bean to the @Configuration class
@Bean
UndertowEmbeddedServletContainerFactory embeddedServletContainerFactory() {
    
    UndertowEmbeddedServletContainerFactory factory = new UndertowEmbeddedServletContainerFactory();
    
    // Other configurations can also be made here.
    factory.addBuilderCustomizers(builder -> builder.setServerOption(UndertowOptions.ENABLE_HTTP2, true));
    
    return factory;
}

Configure Undertow

# Undertow Log Storage Directory
server.undertow.accesslog.dir
# Whether to start the log
server.undertow.accesslog.enabled=false 
# Log format
server.undertow.accesslog.pattern=common
# Prefix of log file name
server.undertow.accesslog.prefix=access_log
# Log file name suffix
server.undertow.accesslog.suffix=log
# Maximum size of HTTP POST requests
server.undertow.max-http-post-size=0 
# Set the number of IO threads, which mainly perform non-blocking tasks. They are responsible for multiple connections. By default, one thread per CPU core is set.
server.undertow.io-threads=4
# Blocking Task Thread Pool. When performing a servlet-like request blocking operation, undertow retrieves threads from this thread pool. Its value setting depends on the load of the system.
server.undertow.worker-threads=20
# The following configuration affects buffer, which is used for server connection IO operations, somewhat similar to netty's pooled memory management
# The smaller the size of each buffer, the more fully it will be utilized.
server.undertow.buffer-size=1024
# The number of buffers allocated per region, so the size of the pool is buffer-size * buffers-per-region
server.undertow.buffers-per-region=1024
# Whether direct memory is allocated or not
server.undertow.direct-buffers=true