深入SpringBoot:自定义Endpoint

Endpoint

SpringBoot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，MetricsEndpoint则会监控内存和gc的状况。
Endpoint的接口如下，其中invoke()是主要的方法，用于返回监控的内容，isSensitive()用于权限控制。


    public interface Endpoint<T> {String getId();boolean isEnabled();boolean isSensitive();T invoke();}

Endpoint的加载还是依靠spring.factories实现的。spring-boot-actuator包下的META-INF/spring.factories配置了EndpointAutoConfiguration。

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
...
org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration,\
...

EndpointAutoConfiguration就会注入必要的Endpoint。有些Endpoint需要外部的收集类，比如TraceEndpoint。

    @Bean@ConditionalOnMissingBeanpublic TraceEndpoint traceEndpoint() {return new TraceEndpoint(this.traceRepository);}

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。

TraceRepository用于保存和获取Request和Response的状态。

 public interface TraceRepository {List<Trace> findAll();void add(Map<String, Object> traceInfo);}

WebRequestTraceFilter用于嵌入web request，收集请求的状态并保存在TraceRepository中。

TraceEndpoint，invoke()方法直接调用TraceRepository保存的数据。

 public class TraceEndpoint extends AbstractEndpoint<List<Trace>> {private final TraceRepository repository;public TraceEndpoint(TraceRepository repository) {super("trace");Assert.notNull(repository, "Repository must not be null");this.repository = repository;}public List<Trace> invoke() {return this.repository.findAll();}}

Endpoint的Mvc接口主要是通过EndpointWebMvcManagementContextConfiguration实现的，这个类的配置也放在spring.factories中。

...
org.springframework.boot.actuate.autoconfigure.ManagementContextConfiguration=\
org.springframework.boot.actuate.autoconfigure.EndpointWebMvcManagementContextConfiguration,\
org.springframework.boot.actuate.autoconfigure.EndpointWebMvcHypermediaManagementContextConfiguration

EndpointWebMvcManagementContextConfiguration注入EndpointHandlerMapping来实现Endpoint的Mvc接口。

    @Bean@ConditionalOnMissingBeanpublic EndpointHandlerMapping endpointHandlerMapping() {Set<? extends MvcEndpoint> endpoints = mvcEndpoints().getEndpoints();CorsConfiguration corsConfiguration = getCorsConfiguration(this.corsProperties);EndpointHandlerMapping mapping = new EndpointHandlerMapping(endpoints,corsConfiguration);boolean disabled = this.managementServerProperties.getPort() != null && this.managementServerProperties.getPort() == -1;mapping.setDisabled(disabled);if (!disabled) {mapping.setPrefix(this.managementServerProperties.getContextPath());}if (this.mappingCustomizers != null) {for (EndpointHandlerMappingCustomizer customizer : this.mappingCustomizers) {customizer.customize(mapping);}}return mapping;}

自定义Endpoint

自定义Endpoint也是类似的原理。这里自定义Endpoint实现应用内存的定时收集。完整的代码放在Github上了。

收集内存，MemStatus是内存的存储结构，MemCollector是内存的收集类，使用Spring内置的定时功能，每5秒收集当前内存。

 public static class MemStatus {public MemStatus(Date date, Map<String, Object> status) {this.date = date;this.status = status;}private Date date;private Map<String, Object> status;public Date getDate() {return date;}public Map<String, Object> getStatus() {return status;}}

 public static class MemCollector {private int maxSize = 5;private List<MemStatus> status;public MemCollector(List<MemStatus> status) {this.status = status;}@Scheduled(cron = "0/5 * *  * * ? ")public void collect() {Runtime runtime = Runtime.getRuntime();Long maxMemory = runtime.maxMemory();Long totalMemory = runtime.totalMemory();Map<String, Object> memoryMap = new HashMap<String, Object>(2, 1);Date date = Calendar.getInstance().getTime();memoryMap.put("maxMemory", maxMemory);memoryMap.put("totalMemory", totalMemory);if (status.size() > maxSize) {status.remove(0);status.add(new MemStatus(date, memoryMap));} else {status.add(new MemStatus(date, memoryMap));}}}

自定义Endpoint，getId是EndPoint的唯一标识，也是Mvc接口对外暴露的路径。invoke方法，取出maxMemory和totalMemory和对应的时间。

 public static class MyEndPoint implements Endpoint {private List<MemStatus> status;public MyEndPoint(List<MemStatus> status) {this.status = status;}public String getId() {return "my";}public boolean isEnabled() {return true;}public boolean isSensitive() {return false;}public Object invoke() {if (status == null || status.isEmpty()) {return "hello world";}Map<String, List<Map<String, Object>>> result = new HashMap<String, List<Map<String, Object>>>();for (MemStatus memStatus : status) {for (Map.Entry<String, Object> entry : memStatus.status.entrySet()) {List<Map<String, Object>> collectList = result.get(entry.getKey());if (collectList == null) {collectList = new LinkedList<Map<String, Object>>();result.put(entry.getKey(), collectList);}Map<String, Object> soloCollect = new HashMap<String, Object>();soloCollect.put("date", memStatus.getDate());soloCollect.put(entry.getKey(), entry.getValue());collectList.add(soloCollect);}}return result;}}

AutoConfig，注入了MyEndPoint，和MemCollector。


 public static class EndPointAutoConfig {private List<MemStatus> status = new ArrayList<MemStatus>();@Beanpublic MyEndPoint myEndPoint() {return new MyEndPoint(status);}@Beanpublic MemCollector memCollector() {return new MemCollector(status);}}

程序入口，运行后访问http://localhost:8080/my 就可以看到了。

 @Configuration@EnableAutoConfigurationpublic class CustomizeEndPoint {public static void main(String[] args) {SpringApplication application = new SpringApplication(CustomizeEndPoint.class);application.run(args);}}

结语

Endpoint也是通过spring.factories实现扩展功能，注入了对应的Bean来实现应用监控的功能。