1. 简介
Spring Boot的Endpoint主要是用来监控应用服务的运行状况，并集成在MVC中提供查看接口。内置的Endpoint比如HealthEndpoint会监控dist和db的状况
2. 分析
2.1 Endpoint源码
Endpoint是在包org.springframework.boot.actuate.endpoint下，其中**invoke()**是最主要的方法，用于返回监控的内容，isSensitive()用于权限控制。核心代码如下：
public interface Endpoint<T> {
String getId();
boolean isEnabled();
boolean isSensitive();
T invoke();
}
2.2 Endpoint加载实现
Endpoint的加载还是要依靠spring.factories实现的。Spring-boot-actutor包下的META-IN/spring.factories配置了EndpointAutoConfiguration。
spring.factories代码如下
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.actuate.autoconfigure.AuditAutoConfiguration,\
org.springframework.boot.actuate.autoconfigure.CacheStatisticsAutoConfiguration,\
org.springframework.boot.actuate.autoconfigure.CrshAutoConfiguration,\
2.3 EndpointAutoConfiguration自动加载类
EndpointAutoConfiguration（org.springframework.boot.actuate.autoconfigure包下）就会注入必要的Endpoint。有些Endpoint需要外部的收集类，比如TraceEndpoint。
* Copyright 2012-2016 the original author or authors.
package org.springframework.boot.actuate.autoconfigure;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import liquibase.integration.spring.SpringLiquibase;
import org.flywaydb.core.Flyway;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.actuate.endpoint.AutoConfigurationReportEndpoint;
import org.springframework.boot.actuate.endpoint.BeansEndpoint;
import org.springframework.boot.actuate.endpoint.ConfigurationPropertiesReportEndpoint;
import org.springframework.boot.actuate.endpoint.DumpEndpoint;
import org.springframework.boot.actuate.endpoint.Endpoint;
import org.springframework.boot.actuate.endpoint.EndpointProperties;
import org.springframework.boot.actuate.endpoint.EnvironmentEndpoint;
import org.springframework.boot.actuate.endpoint.FlywayEndpoint;
import org.springframework.boot.actuate.endpoint.HealthEndpoint;
import org.springframework.boot.actuate.endpoint.InfoEndpoint;
import org.springframework.boot.actuate.endpoint.LiquibaseEndpoint;
import org.springframework.boot.actuate.endpoint.LoggersEndpoint;
import org.springframework.boot.actuate.endpoint.MetricsEndpoint;
import org.springframework.boot.actuate.endpoint.PublicMetrics;
import org.springframework.boot.actuate.endpoint.RequestMappingEndpoint;
import org.springframework.boot.actuate.endpoint.ShutdownEndpoint;
import org.springframework.boot.actuate.endpoint.TraceEndpoint;
import org.springframework.boot.actuate.health.HealthAggregator;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.boot.actuate.health.OrderedHealthAggregator;
import org.springframework.boot.actuate.info.InfoContributor;
import org.springframework.boot.actuate.trace.InMemoryTraceRepository;
import org.springframework.boot.actuate.trace.TraceRepository;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.SearchStrategy;
import org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration;
import org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.boot.logging.LoggingSystem;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.web.servlet.handler.AbstractHandlerMethodMapping;
/**
* {@link EnableAutoConfiguration Auto-configuration} for common management
* {@link Endpoint}s.
*
* @author Dave Syer
* @author Phillip Webb
* @author Greg Turnquist
* @author Christian Dupuis
* @author Stephane Nicoll
* @author Eddú Meléndez
* @author Meang Akira Tanaka
* @author Ben Hale
*/
@Configuration
@AutoConfigureAfter({ FlywayAutoConfiguration.class, LiquibaseAutoConfiguration.class })
@EnableConfigurationProperties(EndpointProperties.class)
public class EndpointAutoConfiguration {
private final HealthAggregator healthAggregator;
private final Map<String, HealthIndicator> healthIndicators;
private final List<InfoContributor> infoContributors;
private final Collection<PublicMetrics> publicMetrics;
private final TraceRepository traceRepository;
public EndpointAutoConfiguration(ObjectProvider<HealthAggregator> healthAggregator,
ObjectProvider<Map<String, HealthIndicator>> healthIndicators,
ObjectProvider<List<InfoContributor>> infoContributors,
ObjectProvider<Collection<PublicMetrics>> publicMetrics,
ObjectProvider<TraceRepository> traceRepository) {
this.healthAggregator = healthAggregator.getIfAvailable();
this.healthIndicators = healthIndicators.getIfAvailable();
this.infoContributors = infoContributors.getIfAvailable();
this.publicMetrics = publicMetrics.getIfAvailable();
this.traceRepository = traceRepository.getIfAvailable();
}
@Bean
@ConditionalOnMissingBean
public EnvironmentEndpoint environmentEndpoint() {
return new EnvironmentEndpoint();
}
@Bean
@ConditionalOnMissingBean
public HealthEndpoint healthEndpoint() {
return new HealthEndpoint(
this.healthAggregator == null ? new OrderedHealthAggregator()
: this.healthAggregator,
this.healthIndicators == null
? Collections.<String, HealthIndicator>emptyMap()
: this.healthIndicators);
}
@Bean
@ConditionalOnMissingBean
public BeansEndpoint beansEndpoint() {
return new BeansEndpoint();
}
@Bean
@ConditionalOnMissingBean
public InfoEndpoint infoEndpoint() throws Exception {
return new InfoEndpoint(this.infoContributors == null
? Collections.<InfoContributor>emptyList() : this.infoContributors);
}
@Bean
@ConditionalOnBean(LoggingSystem.class)
@ConditionalOnMissingBean
public LoggersEndpoint loggersEndpoint(LoggingSystem loggingSystem) {
return new LoggersEndpoint(loggingSystem);
}
@Bean
@ConditionalOnMissingBean
public MetricsEndpoint metricsEndpoint() {
List<PublicMetrics> publicMetrics = new ArrayList<PublicMetrics>();
if (this.publicMetrics != null) {
publicMetrics.addAll(this.publicMetrics);
}
Collections.sort(publicMetrics, AnnotationAwareOrderComparator.INSTANCE);
return new MetricsEndpoint(publicMetrics);
}
@Bean
@ConditionalOnMissingBean
public TraceEndpoint traceEndpoint() {
return new TraceEndpoint(this.traceRepository == null
? new InMemoryTraceRepository() : this.traceRepository);
}
@Bean
@ConditionalOnMissingBean
public DumpEndpoint dumpEndpoint() {
return new DumpEndpoint();
}
@Bean
@ConditionalOnBean(ConditionEvaluationReport.class)
@ConditionalOnMissingBean(search = SearchStrategy.CURRENT)
public AutoConfigurationReportEndpoint autoConfigurationReportEndpoint() {
return new AutoConfigurationReportEndpoint();
}
@Bean
@ConditionalOnMissingBean
public ShutdownEndpoint shutdownEndpoint() {
return new ShutdownEndpoint();
}
@Bean
@ConditionalOnMissingBean
public ConfigurationPropertiesReportEndpoint configurationPropertiesReportEndpoint() {
return new ConfigurationPropertiesReportEndpoint();
}
@Configuration
@ConditionalOnBean(Flyway.class)
@ConditionalOnClass(Flyway.class)
static class FlywayEndpointConfiguration {
@Bean
@ConditionalOnMissingBean
public FlywayEndpoint flywayEndpoint(Map<String, Flyway> flyways) {
return new FlywayEndpoint(flyways);
}
}
@Configuration
@ConditionalOnBean(SpringLiquibase.class)
@ConditionalOnClass(SpringLiquibase.class)
static class LiquibaseEndpointConfiguration {
@Bean
@ConditionalOnMissingBean
public LiquibaseEndpoint liquibaseEndpoint(
Map<String, SpringLiquibase> liquibases) {
return new LiquibaseEndpoint(liquibases);
}
}
@Configuration
@ConditionalOnClass(AbstractHandlerMethodMapping.class)
protected static class RequestMappingEndpointConfiguration {
@Bean
@ConditionalOnMissingBean
public RequestMappingEndpoint requestMappingEndpoint() {
RequestMappingEndpoint endpoint = new RequestMappingEndpoint();
return endpoint;
}
}
}
TraceEndpoint会记录每次请求的Request和Response的状态，需要嵌入到Request的流程中，这里就主要用到了3个类。
2.4 TraceRepository用于保存和获取Request和Response的状态。
* Copyright 2012-2015 the original author or authors.
package org.springframework.boot.actuate.trace;
import java.util.List;
import java.util.Map;
/**
* A repository for {@link Trace}s.
*
* @author Dave Syer
*/
public interface TraceRepository {
/**
* Find all {@link Trace} objects contained in the repository.
* @return the results
*/
List<Trace> findAll();
/**
* Add a new {@link Trace} object at the current time.
* @param traceInfo trace information
*/
void add(Map<String, Object> traceInfo);
}
2.5 WebRequestTraceFilter用于嵌入web request，收集请求的状态并保存在TraceRepository中。
2.6 TraceEndpoint，invoke()方法直接调用TraceRepository保存的数据。
* Copyright 2012-2016 the original author or authors.
package org.springframework.boot.actuate.endpoint;
import java.util.List;
import org.springframework.boot.actuate.trace.Trace;
import org.springframework.boot.actuate.trace.TraceRepository;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.util.Assert;
/**
* {@link Endpoint} to expose {@link Trace} information.
*
* @author Dave Syer
*/
@ConfigurationProperties(prefix = "endpoints.trace")
public class TraceEndpoint extends AbstractEndpoint<List<Trace>> {
private final TraceRepository repository;
/**
* Create a new {@link TraceEndpoint} instance.
* @param repository the trace repository
*/
public TraceEndpoint(TraceRepository repository) {
super("trace");
Assert.notNull(repository, "Repository must not be null");
this.repository = repository;
}
@Override
public List<Trace> invoke() {
return this.repository.findAll();
}
}
3. 总结
很多spring-starter都是基于是spring.factories的配置实现，可以完美的提高复用性，模块化开发。可以利用好endpoint实现不少的监控统计功能
