在最新的 spring boot 2.3 版本，内置了优雅停机功能
server:
shutdown: graceful # 开启优雅停机，默认使用IMMEDIATE立即关机
spring:
lifecycle:
timeout-per-shutdown-phase: 30s # 设置缓冲区，最大等待时间,超时候无论线程任务是否执行完毕都会停机处理,默认30s
模拟一个耗时请求
@GetMapping("/")
public String hello() throws InterruptedException {
Thread.sleep(20 * 1000L);
return "hello";
}
在执行优雅关键后，日志如下，耗时请求也收到了返回值
[extShutdownHook] o.s.b.w.e.tomcat.GracefulShutdown : Commencing graceful shutdown. Waiting for active requests to complete
[tomcat-shutdown] o.s.b.w.e.tomcat.GracefulShutdown : Graceful shutdown complete
[extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'
我们可以通过Spring Boot提供了shutdown的actuator来触发关闭操作，默认是关闭的
management:
endpoint:
shutdown:
enabled: true
endpoints:
web:
exposure:
include: shutdown
