SpringBoot Actuator、Prometheus 源码分析

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1、pom引入jar，配置yml

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端点如果加载，暴露 ===> 指标

【启动】
spring-boot-starter-actuator
    spring-boot-actuator-autoconfigure

spring.factories - WebEndpointAutoConfiguration
    WebEndpointDiscoverer
    ControllerEndpointDiscoverer
    ServletEndpointDiscoverer
    PathMappedEndpoints
        --- 调用所有 Discoverer getEndpoints
        --- createEndpointBeans() @Endpoint
        --- isEndpointExposed 是否暴露端点
        --- addOperations 生成Operation
spring.factories - WebMvcEndpointManagementContextConfiguration
    WebMvcEndpointHandlerMapping
        EndpointLinksResolver   resolveLinks(String requestUrl)

【访问】
    DispatcherServlet doDispatch
    RequestMappingHandlerAdapter invokeHandlerMethod
    ServletInvocableHandlerMethod invokeAndHandle
    ===> WebMvcEndpointHandlerMapping    EndpointLinksResolver   resolveLinks(String requestUrl)
    
    ExposableWebEndpoint   Collection<O> getOperations(); ===> Operation   扩展路径
    PathMappedEndpoint     String getRootPath() ===> /actuator   根路径
    
    AbstractWebMvcEndpointHandlerMapping.ServletWebOperationAdapter handle
    HealthEndpointWebExtension health

2、health ===> 健康-可用

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http://127.0.0.1:18006/actuator/health

DispatcherServlet doDispatch
RequestMappingHandlerAdapter invokeHandlerMethod
ServletInvocableHandlerMethod invokeAndHandle
AbstractWebMvcEndpointHandlerMapping.ServletWebOperationAdapter handle
HealthEndpointWebExtension health

3、集成prometheus 暴露端点

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PrometheusMetricsExportAutoConfiguration      @ConditionalOnClass(PrometheusMeterRegistry.class)

PrometheusMeterRegistry


-- 默认绑定 ------------------------------
MetricsAutoConfiguration   -> MeterRegistryPostProcessor

        postProcessAfterInitialization -> PrometheusMeterRegistry Bean 会进入
        
        addBinders(registry); ===> binder.bindTo(registry)
-- Tomcat绑定（项目启动时，监听事件） ------------------------------
    TomcatMetricsBinder         implements ApplicationListener<ApplicationStartedEvent>
            @Override
            public void onApplicationEvent(ApplicationStartedEvent event) {
                ApplicationContext applicationContext = event.getApplicationContext();
                Manager manager = findManager(applicationContext);
                this.tomcatMetrics = new TomcatMetrics(manager, this.tags);
                this.tomcatMetrics.bindTo(this.meterRegistry);
            }
	
    TomcatMetrics
            @Override
            public void bindTo(MeterRegistry registry) {
                registerGlobalRequestMetrics(registry);
                registerServletMetrics(registry);
                registerCacheMetrics(registry);
                registerThreadPoolMetrics(registry);
                registerSessionMetrics(registry);
            }

4、数据动态化

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lambda表达式  ===> TomcatMetrics

Gauge.builder("tomcat.sessions.active.max", manager, Manager::getMaxActive)
        .tags(tags)
        .baseUnit(BaseUnits.SESSIONS)
        .register(registry);

5、独立端口原理

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management.server.port=17006   异端口（独享线程池）    ManagementServerPortUtils.ManagementServerPort
同端口，异端口

ManagementContextAutoConfiguration

SameManagementContextConfiguration        @ConditionalOnManagementPort(ManagementPortType.SAME)
    EnableSameManagementContextConfiguration   @EnableManagementContext(ManagementContextType.SAME)

-- 主容器打满，子容器还能继续使用
DifferentManagementContextConfiguration   @ConditionalOnManagementPort(ManagementPortType.DIFFERENT)
    EnableChildManagementContextConfiguration  @EnableManagementContext(ManagementContextType.CHILD)
        ServletManagementContextFactory.createManagementContext
            registerServletWebServerFactory(parent, child);
            determineServletWebServerFactoryClass(parent) --- 确定 Tomcat 、 Jetty 、 Undertow
        managementContext.refresh();


-- 异端口，新DispatcherServlet
@EnableManagementContext(ManagementContextType.CHILD) ===> @Import(ManagementContextConfigurationImportSelector.class)

protected List<String> loadFactoryNames() {
    return SpringFactoriesLoader.loadFactoryNames(ManagementContextConfiguration.class, this.classLoader);
}

WebMvcEndpointChildContextConfiguration
    @Bean(name = DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
    DispatcherServlet dispatcherServlet() {
        DispatcherServlet dispatcherServlet = new DispatcherServlet();
        ...
        return dispatcherServlet;
    }