Endpoint

SpringBoot的Endpoint主要是用來監控應用服務的運行狀況，并集成在Mvc中提供查看接口。內置的Endpoint比如HealthEndpoint會監控dist和db的狀況，MetricsEndpoint則會監控內存和gc的狀況。
Endpoint的接口如下，其中invoke()是主要的方法，用于返回監控的內容，isSensitive()用于權限控制。

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

Endpoint的加載還是依靠spring.factories實現的。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就會注入必要的Endpoint。有些Endpoint需要外部的收集類，比如TraceEndpoint。

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

TraceEndpoint會記錄每次請求的Request和Response的狀態，需要嵌入到Request的流程中，這里就主要用到了3個類。

TraceRepository用于保存和獲取Request和Response的狀態。 public interface TraceRepository {List<Trace> findAll();void add(Map<String, Object> traceInfo);}

WebRequestTraceFilter用于嵌入web request，收集請求的狀態并保存在TraceRepository中。

TraceEndpoint，invoke()方法直接調用TraceRepository保存的數據。 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接口主要是通過EndpointWebMvcManagementContextConfiguration實現的，這個類的配置也放在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來實現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;}

自定義Endpoint

自定義Endpoint也是類似的原理。這里自定義Endpoint實現應用內存的定時收集。完整的代碼放在Github上了。

收集內存，MemStatus是內存的存儲結構，MemCollector是內存的收集類，使用Spring內置的定時功能，每5秒收集當前內存。 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));}}}

自定義Endpoint，getId是EndPoint的唯一標識，也是Mvc接口對外暴露的路徑。invoke方法，取出maxMemory和totalMemory和對應的時間。 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，運行后訪問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);}}

結語

Endpoint也是通過spring.factories實現擴展功能，注入了對應的Bean來實現應用監控的功能。

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