代码更新不停机:SpringBoot应用实现零停机更新的新质生产力
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·
2024-07-31 07:25
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设计思路
-
SpringBoot内嵌Servlet容器的原理是什么 -
DispatcherServlet是如何传递给Servlet容器的
public class Main {
public static void main(String[] args) {
try {
Tomcat tomcat =new Tomcat();
tomcat.getConnector();
tomcat.getHost();
Context context = tomcat.addContext("/", null);
tomcat.addServlet("/","index",new HttpServlet(){
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.getWriter().append("hello");
}
});
context.addServletMappingDecoded("/","index");
tomcat.init();
tomcat.start();
}catch (Exception e){}
}
}
TomcatServletWebServerFactory
。
private static ServletWebServerFactory getWebServerFactory(ConfigurableApplicationContext context) {
String[] beanNames = context.getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);
return context.getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}
ServletWebServerFactory.getWebServer
就可以获取一个Web服务,他有start、stop方法启动、关闭Web服务。
tomcat.addServlet
把DispatcherServlet传递给Tomcat,而是通过个Tomcat主动回调来完成的,具体的回调通过ServletContainerInitializer
接口协议,它允许我们动态地配置Servlet、过滤器。
TomcatStarter
,但是TomcatStarter
也只是一堆SpringBoot内部ServletContextInitializer
的集合,简单的封装了一下,这些集合中有一个类会向Tomcat添加DispatcherServlet
ServletContextInitializer
集合来初始化,
ServletContextInitializer
集合。
ServletContextInitializer
集合?
ServletContextInitializerBeans
是实现Collection
的。
protected static Collection<ServletContextInitializer> getServletContextInitializerBeans(ConfigurableApplicationContext context) {
return new ServletContextInitializerBeans(context.getBeanFactory());
}
-
判断端口是否占用 -
占用则先通过其他端口启动 -
等待启动完毕后终止老进程 -
重新创建容器实例并且关联DispatcherServlet
实现代码
@SpringBootApplication()
@EnableScheduling
public class WebMainApplication {
public static void main(String[] args) {
String[] newArgs = args.clone();
int defaultPort = 8088;
boolean needChangePort = false;
if (isPortInUse(defaultPort)) {
newArgs = new String[args.length + 1];
System.arraycopy(args, 0, newArgs, 0, args.length);
newArgs[newArgs.length - 1] = "--server.port=9090";
needChangePort = true;
}
ConfigurableApplicationContext run = SpringApplication.run(WebMainApplication.class, newArgs);
if (needChangePort) {
String command = String.format("lsof -i :%d | grep LISTEN | awk '{print $2}' | xargs kill -9", defaultPort);
try {
Runtime.getRuntime().exec(new String[]{"sh", "-c", command}).waitFor();
while (isPortInUse(defaultPort)) {
}
ServletWebServerFactory webServerFactory = getWebServerFactory(run);
((TomcatServletWebServerFactory) webServerFactory).setPort(defaultPort);
WebServer webServer = webServerFactory.getWebServer(invokeSelfInitialize(((ServletWebServerApplicationContext) run)));
webServer.start();
((ServletWebServerApplicationContext) run).getWebServer().stop();
} catch (IOException | InterruptedException ignored) {
}
}
}
private static ServletContextInitializer invokeSelfInitialize(ServletWebServerApplicationContext context) {
try {
Method method = ServletWebServerApplicationContext.class.getDeclaredMethod("getSelfInitializer");
method.setAccessible(true);
return (ServletContextInitializer) method.invoke(context);
} catch (Throwable e) {
throw new RuntimeException(e);
}
}
private static boolean isPortInUse(int port) {
try (ServerSocket serverSocket = new ServerSocket(port)) {
return false;
} catch (IOException e) {
return true;
}
}
protected static Collection<ServletContextInitializer> getServletContextInitializerBeans(ConfigurableApplicationContext context) {
return new ServletContextInitializerBeans(context.getBeanFactory());
}
private static ServletWebServerFactory getWebServerFactory(ConfigurableApplicationContext context) {
String[] beanNames = context.getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);
return context.getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}
}
测试
@RestController()
@RequestMapping("port/test")
public class TestPortController {
@GetMapping("test")
public String test() {
return "1";
}
}
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