Spring环境下如何仅将Liveness Probe移至独立端口或线程池？

方案一：为Liveness端点分配独立线程池（无需修改端口） #

这种方式无需额外端口，仅让Liveness探针请求使用独立线程池，避免被主线程池的高负载阻塞；同时Readiness探针仍使用主线程池，能准确反映应用的负载状态。

1. 定义独立线程池Bean
   创建专门处理Liveness探针请求的线程池：

@Bean(name = "livenessTaskExecutor")
public TaskExecutor livenessTaskExecutor() {
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(2); // 根据实际需求调整核心线程数
    executor.setMaxPoolSize(5); // 最大线程数
    executor.setQueueCapacity(10); // 任务队列容量
    executor.setThreadNamePrefix("liveness-probe-"); // 线程名前缀，便于排查问题
    executor.initialize();
    return executor;
}

2. 配置MVC路由，仅对Liveness端点应用该线程池
   通过WebMvc配置，限定只有Liveness端点的请求使用上述独立线程池：

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    @Autowired
    @Qualifier("livenessTaskExecutor")
    private TaskExecutor livenessTaskExecutor;

    @Override
    public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
        configurer.setTaskExecutor(livenessTaskExecutor);
        // 拦截请求，仅对Liveness端点启用异步线程池
        configurer.registerCallableInterceptors(new CallableProcessingInterceptor() {
            @Override
            public <T> boolean isAsyncRequest(HttpServletRequest request, Callable<T> task) {
                return request.getRequestURI().equals("/actuator/health/liveness");
            }
        });
    }
}

配置后，主线程池高负载时，Readiness探针会因响应缓慢被判定为未就绪，Pod被移出流量池；而Liveness探针使用独立线程池，能快速响应，避免Pod被误杀。

方案二：将Liveness端点单独部署到独立端口 #

如果业务场景要求必须将Liveness探针放在独立端口，可通过Spring Boot多WebServer配置实现：主应用端口承载Readiness探针，独立端口仅提供Liveness端点服务。

1. 添加自定义配置属性
   在application.properties中定义Liveness端口：

management.liveness.server.port=9091

2. 配置独立WebServer用于Liveness端点
   创建配置类，启动第二个WebServer，仅注册Liveness相关的Actuator端点：

@Configuration
public class LivenessServerConfig {
    @Value("${management.liveness.server.port:9091}")
    private int livenessPort;

    @Bean
    public ServletWebServerFactory livenessServerFactory() {
        TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory(livenessPort);
        factory.addInitializers(servletContext -> {
            // 初始化仅用于Liveness端点的DispatcherServlet
            DispatcherServlet dispatcherServlet = new DispatcherServlet();
            AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
            context.register(LivenessEndpointConfig.class);
            dispatcherServlet.setApplicationContext(context);
            // 仅映射Liveness端点路径
            servletContext.addServlet("livenessDispatcher", dispatcherServlet)
                    .addMapping("/actuator/health/liveness");
        });
        return factory;
    }

    // 仅配置Liveness所需的Actuator组件
    @Configuration
    static class LivenessEndpointConfig {
        @Bean
        public HealthEndpoint healthEndpoint(HealthAggregator healthAggregator, HealthIndicatorRegistry registry) {
            return new HealthEndpoint(healthAggregator, registry);
        }

        @Bean
        public LivenessHealthIndicator livenessHealthIndicator() {
            return new LivenessHealthIndicator();
        }

        @Bean
        public EndpointMapping endpointMapping() {
            return new EndpointMapping("/actuator");
        }

        @Bean
        public WebMvcEndpointHandlerMapping webMvcEndpointHandlerMapping(EndpointMapping endpointMapping,
                                                                         List<ExposableEndpoint<?>> endpoints,
                                                                         EndpointMediaTypes endpointMediaTypes,
                                                                         CorsEndpointProperties corsProperties,
                                                                         WebEndpointProperties webEndpointProperties) {
            return new WebMvcEndpointHandlerMapping(endpointMapping, endpoints, endpointMediaTypes,
                    corsProperties.toCorsConfiguration(), webEndpointProperties);
        }
    }
}

配置完成后，Kubernetes的Readiness探针指向主应用端口的/actuator/health/readiness，Liveness探针指向9091端口的/actuator/health/liveness，两者完全独立，互不影响。

内容的提问来源于stack exchange，提问作者Shachar Levy