Spring Cloud Gateway 启动流程源码分析
作者：万物皆字节
以下分析以 spring-cloud-starter-gateway 4.1.0 源码为分析样本。
配置和启动类
如果我们要使用 Spring Cloud Gateway，需要在pom里引入如下依赖：
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-gateway</artifactId> <version>4.1.0</version> </dependency>
spring-cloud-starter-gateway里的依赖如下：
<dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-gateway-server</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-loadbalancer</artifactId> <optional>true</optional> </dependency> </dependencies>
看上面引入了 spring-boot-starter-webflux，为后面分析做铺垫；
除了引入依赖，我们还需要有一个启动类，如下：
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@EnableDiscoveryClient
@Slf4j
@SpringBootApplication
public class XXGatewayApp {
public static void main(String[] args) {
SpringApplication.run(XXGatewayApp.class, args);
log.info("XX网关启动成功！");
}
}启动 nettyserver
在主类启动后，是如何启动一个nettyserver的，我们来分析一下；跟踪启动类代码来到如下方法：
org.springframework.boot.SpringApplication#run(java.lang.String…)
public ConfigurableApplicationContext run(String... args) {
Startup startup = SpringApplication.Startup.create();
if (this.registerShutdownHook) {
shutdownHook.enableShutdownHookAddition();
}
... 省略代码...
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, bootstrapContext, applicationArguments);
Banner printedBanner = this.printBanner(environment);
// @A1 创建 ConfigurableApplicationContext
context = this.createApplicationContext();
context.setApplicationStartup(this.applicationStartup);
this.prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
// @A2 触发创建server
this.refreshContext(context);
... 省略代码...
} catch (Throwable ex) {
if (ex instanceof AbandonedRunException) {
throw ex;
}
this.handleRunFailure(context, ex, listeners);
throw new IllegalStateException(ex);
}
try {
if (context.isRunning()) {
listeners.ready(context, startup.ready());
}
return context;
} catch (Throwable ex) {
if (ex instanceof AbandonedRunException) {
throw ex;
} else {
this.handleRunFailure(context, ex, (SpringApplicationRunListeners)null);
throw new IllegalStateException(ex);
}
}
}@A1：这个方法会执行以下逻辑
org.springframework.boot.WebApplicationType#deduceFromClasspath
计算web容器类型，而最上面的pom依赖引入了 spring-boot-starter-webflux
static WebApplicationType deduceFromClasspath() {
if (ClassUtils.isPresent("org.springframework.web.reactive.DispatcherHandler", (ClassLoader)null) && !ClassUtils.isPresent("org.springframework.web.servlet.DispatcherServlet", (ClassLoader)null) && !ClassUtils.isPresent("org.glassfish.jersey.servlet.ServletContainer", (ClassLoader)null)) {
return REACTIVE;
} else {
for(String className : SERVLET_INDICATOR_CLASSES) {
if (!ClassUtils.isPresent(className, (ClassLoader)null)) {
return NONE;
}
}
return SERVLET;
}
}上面代码根据类路径中加入的依赖，返回REACTIVE，最终返回 org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext 对象
创建websever
接上面 @A2方法，会触发AnnotationConfigReactiveWebServerApplicationContext如下调用：
注：AnnotationConfigReactiveWebServerApplicationContext父类是
ReactiveWebServerApplicationContext#createWebServer
private void createWebServer() {
WebServerManager serverManager = this.serverManager;
if (serverManager == null) {
StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");
String webServerFactoryBeanName = this.getWebServerFactoryBeanName();
//@B1 创建ReactiveWebServerFactory ，创建server的核心点
ReactiveWebServerFactory webServerFactory = this.getWebServerFactory(webServerFactoryBeanName);
createWebServer.tag("factory", webServerFactory.getClass().toString());
boolean lazyInit = this.getBeanFactory().getBeanDefinition(webServerFactoryBeanName).isLazyInit();
//@B2 WebServerManager构造方法创建server
this.serverManager = new WebServerManager(this, webServerFactory, this::getHttpHandler, lazyInit);
this.getBeanFactory().registerSingleton("webServerGracefulShutdown", new WebServerGracefulShutdownLifecycle(this.serverManager.getWebServer()));
//@B3 很绝的方法
this.getBeanFactory().registerSingleton("webServerStartStop", new WebServerStartStopLifecycle(this.serverManager));
createWebServer.end();
}
this.initPropertySources();
}@B1 方法很绕，会从ReactiveWebServerFactoryConfiguration里去获得NettyReactiveWebServerFactory的bean定义，而这个bean定义依赖 ReactorResourceFactory ，代码如下：
@Bean
NettyReactiveWebServerFactory nettyReactiveWebServerFactory(ReactorResourceFactory resourceFactory, ObjectProvider<NettyRouteProvider> routes, ObjectProvider<NettyServerCustomizer> serverCustomizers) {
NettyReactiveWebServerFactory serverFactory = new NettyReactiveWebServerFactory();
serverFactory.setResourceFactory(resourceFactory);
Stream var10000 = routes.orderedStream();
Objects.requireNonNull(serverFactory);
var10000.forEach((xva$0) -> serverFactory.addRouteProviders(new NettyRouteProvider[]{xva$0}));
serverFactory.getServerCustomizers().addAll(serverCustomizers.orderedStream().toList());
return serverFactory;
}也就是说在容器返回NettyReactiveWebServerFactory 对象前会把ReactorResourceFactory 对象初始化完毕；ReactorResourceFactory 这个类实现了InitializingBean，我们看看afterPropertiesSet方法初始化内容：
public void start() {
synchronized(this.lifecycleMonitor) {
if (!this.isRunning()) {
if (!this.useGlobalResources) {
if (this.loopResources == null) {
this.manageLoopResources = true;
this.loopResources = (LoopResources)this.loopResourcesSupplier.get();
}
if (this.connectionProvider == null) {
this.manageConnectionProvider = true;
this.connectionProvider = (ConnectionProvider)this.connectionProviderSupplier.get();
}
} else {
Assert.isTrue(this.loopResources == null && this.connectionProvider == null, "'useGlobalResources' is mutually exclusive with explicitly configured resources");
// @C1
HttpResources httpResources = HttpResources.get();
if (this.globalResourcesConsumer != null) {
this.globalResourcesConsumer.accept(httpResources);
}
this.connectionProvider = httpResources;
this.loopResources = httpResources;
}
this.running = true;
}
}
}@C1方法最终执行的是 reactor.netty.resources.LoopResources#create(java.lang.String)
static LoopResources create(String prefix) {
if (((String)Objects.requireNonNull(prefix, "prefix")).isEmpty()) {
throw new IllegalArgumentException("Cannot use empty prefix");
} else {
return new DefaultLoopResources(prefix, DEFAULT_IO_SELECT_COUNT, DEFAULT_IO_WORKER_COUNT, true);
}
}是不是很熟悉了，是创建的reactor.netty.resources.DefaultLoopResources 对象
todo~~
@B2 方法会调用到如下方法：
org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory#getWebServer
public WebServer getWebServer(HttpHandler httpHandler) {
// @D1 创建 HttpServer
HttpServer httpServer = this.createHttpServer();
ReactorHttpHandlerAdapter handlerAdapter = new ReactorHttpHandlerAdapter(httpHandler);
NettyWebServer webServer = this.createNettyWebServer(httpServer, handlerAdapter, this.lifecycleTimeout, this.getShutdown());
webServer.setRouteProviders(this.routeProviders);
return webServer;
}@D1 方法会执行到如下方法： org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory#createHttpServer
private HttpServer createHttpServer() {
HttpServer server = HttpServer.create().bindAddress(this::getListenAddress);
if (Ssl.isEnabled(this.getSsl())) {
server = this.customizeSslConfiguration(server);
}
if (this.getCompression() != null && this.getCompression().getEnabled()) {
CompressionCustomizer compressionCustomizer = new CompressionCustomizer(this.getCompression());
server = compressionCustomizer.apply(server);
}
server = server.protocol(this.listProtocols()).forwarded(this.useForwardHeaders);
return this.applyCustomizers(server);
}继续分析上面：@B3
这个地方太绝了，向容器中注入了一个 WebServerStartStopLifecycle，这种类型的类会被框架中触发start方法，触发一些列的start方法，最终执行的是 reactor.netty.http.server.HttpServerBind父类 ----> HttpServer 父类 -----> reactor.netty.transport.ServerTransport的 bindNow方法 ----> bind方法。
重要方法 reactor.netty.transport.ServerTransport#bind
public Mono<? extends DisposableServer> bind() {
CONF config = (CONF)(this.configuration());
Objects.requireNonNull(config.bindAddress(), "bindAddress");
Mono<? extends DisposableServer> mono = Mono.create((sink) -> {
SocketAddress local = (SocketAddress)Objects.requireNonNull((SocketAddress)config.bindAddress().get(), "Bind Address supplier returned null");
if (local instanceof InetSocketAddress) {
InetSocketAddress localInet = (InetSocketAddress)local;
if (localInet.isUnresolved()) {
local = AddressUtils.createResolved(localInet.getHostName(), localInet.getPort());
}
}
boolean isDomainSocket = false;
DisposableBind disposableServer;
if (local instanceof DomainSocketAddress) {
isDomainSocket = true;
disposableServer = new UdsDisposableBind(sink, config, local);
} else {
disposableServer = new InetDisposableBind(sink, config, local);
}
ConnectionObserver childObs = new ChildObserver(config.defaultChildObserver().then(config.childObserver()));
// @E1
Acceptor acceptor = new Acceptor(config.childEventLoopGroup(), config.channelInitializer(childObs, (SocketAddress)null, true), config.childOptions, config.childAttrs, isDomainSocket);
// @E2
TransportConnector.bind(config, new AcceptorInitializer(acceptor), local, isDomainSocket).subscribe(disposableServer);
});
if (config.doOnBind() != null) {
mono = mono.doOnSubscribe((s) -> config.doOnBind().accept(config));
}
return mono;
}@E1：最终调用 reactor.netty.resources.DefaultLoopResources#cacheNioServerLoops 获得work线程池
@E2：最终调用 reactor.netty.resources.DefaultLoopResources#cacheNioSelectLoops 获得boss线程池
问题来了：看reactor.netty.resources.LoopResources源码，如果系统参数里没有配置reactor.netty.ioSelectCount，则boss线程会和work线程池的AtomicReference在cacheNioSelectLoops 方法中返回同一对象；这是不是会造成线程池共用？
可以参看 https://blog.csdn.net/qq_42651904/article/details/134561804 这篇文章理解；
那么你们生产环境会单独设置 reactor.netty.ioSelectCount 参数吗？
jvisualvm监控验证
- 如果不设置reactor.netty.ioSelectCount 这个启动参数，通过监控网关启动后线程名称是 reactor-http-nio-xx
- 如果在启动的时候设置这个参数为1，启动的线程不一样 reactor-http-select-xx
public static void main(String[] args) {
System.setProperty("reactor.netty.ioSelectCount", "1");
SpringApplication.run(XXXGatewayApp.class, args);
log.info("XXX网关启动成功！");
}
设想一下，如果代码写得不好在GlobalFilter有阻塞写法，比如数据查询、redis查询，加上高并发请求，那么是不是会影响boss线程“接客”？
后面再通过压测的方式论证一下。
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