feat: Add comprehensive documentation for integration layer, API design, config governance, observability, build/deploy, and testing strategies

- Introduced integration layer design with Resilience4j for external vendor calls.
- Established API design standards with unified response structures and global exception handling.
- Defined configuration and service governance using Kubernetes native solutions.
- Implemented observability practices including trace ID propagation and structured logging.
- Outlined build and multi-environment deployment strategies using Gradle and GitLab CI/CD.
- Specified testing strategies across different layers, utilizing JUnit, MockK, Testcontainers, and WireMock.
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Guangfei.Zhao
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# 08. 可观测性
## 决策
统一 Trace ID + 结构化(JSON)日志 + Micrometer 指标,对应架构图 `Cross-Cutting` 里的 `Observability` 要求;关键行为单独走审计日志通道,对应 `Audit / Security`
## 结构约定
```
platform-observability/
TraceIdFilter # 入口生成/透传 traceId,写入 MDC
logback-spring.xml # 结构化日志格式配置
MetricsConfig # Micrometer 基础配置,暴露 /actuator/prometheus
AuditLogAspect # AOP 切面,标注 @Audited 的方法自动记录审计日志
```
## `TraceIdFilter` 示例
```kotlin
// platform-observability/.../TraceIdFilter.kt
class TraceIdFilter : OncePerRequestFilter() {
override fun doFilterInternal(request: HttpServletRequest, response: HttpServletResponse, chain: FilterChain) {
val traceId = request.getHeader("X-Trace-Id") ?: UUID.randomUUID().toString()
MDC.put("traceId", traceId)
response.setHeader("X-Trace-Id", traceId)
try {
chain.doFilter(request, response)
} finally {
MDC.clear() // 必须清理,否则线程池复用线程会带出上一个请求的 traceId
}
}
}
object TraceIdHolder {
fun current(): String = MDC.get("traceId") ?: "unknown"
}
```
调用 F6/Mini 域时,把当前 `traceId` 透传到下游请求头,方便跨系统关联日志:
```kotlin
webClient.get()
.uri("/f6/procurement/list")
.header("X-Trace-Id", TraceIdHolder.current())
.retrieve()
// ...
```
## 结构化日志配置示例
```xml
<!-- logback-spring.xml -->
<configuration>
<appender name="JSON" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="net.logstash.logback.encoder.LogstashEncoder">
<includeMdcKeyName>traceId</includeMdcKeyName>
<customFields>{"app":"conti-backend"}</customFields>
</encoder>
</appender>
<root level="INFO">
<appender-ref ref="JSON" />
</root>
</configuration>
```
```groovy
// build.gradle
implementation 'net.logstash.logback:logstash-logback-encoder:7.4'
```
输出的每条日志会带上 `traceId` 字段,直接对接现有 ELK 方案(见 `Architecture-Diagram/ODP ELK Logging Solution Project - Overview.pdf`)时可以直接按 `traceId` 过滤出一次请求的完整链路日志。
## Micrometer / Actuator 配置
```yaml
# application.yml
management:
endpoints:
web:
exposure:
include: health, prometheus, info
endpoint:
health:
probes:
enabled: true # 暴露 /actuator/health/liveness、/readiness,供 K8s 探针使用
```
```groovy
implementation 'org.springframework.boot:spring-boot-starter-actuator'
implementation 'io.micrometer:micrometer-registry-prometheus'
```
## 审计日志示例
```kotlin
// platform-observability/.../Audited.kt
@Target(AnnotationTarget.FUNCTION)
@Retention(AnnotationRetention.RUNTIME)
annotation class Audited(val action: String)
// platform-observability/.../AuditLogAspect.kt
@Aspect
@Component
class AuditLogAspect(private val storeContextHolder: StoreContextHolder) {
private val auditLog = LoggerFactory.getLogger("AUDIT")
@Around("@annotation(audited)")
fun logAudit(joinPoint: ProceedingJoinPoint, audited: Audited): Any? {
val result = runCatching { joinPoint.proceed() }
auditLog.info(
"action={} userId={} storeId={} traceId={} success={}",
audited.action, storeContextHolder.userId, storeContextHolder.storeId,
TraceIdHolder.current(), result.isSuccess,
)
return result.getOrThrow()
}
}
// 使用方式
@Audited(action = "WEBVIEW_TICKET_ISSUE")
fun issueTicket(userId: Long, storeId: Long): WebviewTicket { ... }
```
审计日志走独立 logger`AUDIT`),在 `logback-spring.xml` 里单独配置一个 appender 写到专门的审计日志文件/索引,不和普通业务日志混在一起,方便设置更长的保留期和更严格的访问权限。
## 关键规则
- `traceId` 从入口 filter 生成,贯穿到 `f6-integration` / `mini-clients` 调用外部系统,失败时把 `traceId` 一起返回给前端(已经在 [06-api-design.md](./06-api-design.md) 的 `ApiResult` 里),方便排障(对应架构图 Flow 2 的"失败可支持排障"要求)。
- 审计相关的关键行为(登录、换票、供应商调用失败)走单独的审计日志通道,不和普通业务日志混在一起。
- 日志/指标最终对接现有 ELK 方案,具体接入方式(Filebeat 采集 stdout,还是直接推 Logstash)待确认。
## 附录:为什么要在 MDC 里放 traceId,而不是每条日志手动传参
不用 `MDC` 的话,每个方法打日志都要显式传 `traceId` 参数:`log.info("traceId={} 门店切换成功", traceId)`,深层调用链里每一层都要多加一个参数,代码侵入性很强,还容易漏传。`MDC`Mapped Diagnostic Context)是日志框架提供的"线程内隐式上下文",在 filter 里设置一次,同一线程内后续所有日志调用(不管调用链多深)都会自动带上这个字段,日志格式配置里声明 `includeMdcKeyName` 即可,业务代码完全不需要感知 `traceId` 的传递。
代价和 [04-security-auth.md](./04-security-auth.md) 里提到的 `ThreadLocal` 类似:`MDC` 底层也是 `ThreadLocal` 实现的,异步线程池、协程切换线程的场景需要手动透传(`MDC.getCopyOfContextMap()` 传给子线程),我们当前同步 Servlet 栈下不需要特殊处理,但如果某个模块引入异步处理要注意这一点。
## 待补充
- 具体接入现有 ELK / APM 的方式和字段规范。
- 审计日志的存储和保留策略。
## 参考链接
- [SLF4J MDC 官方文档](https://www.slf4j.org/manual.html#mdc)
- [Micrometer 官方文档](https://docs.micrometer.io/micrometer/reference/)
- [Spring Boot Actuator 官方文档](https://docs.spring.io/spring-boot/reference/actuator/index.html)