> For the complete documentation index, see [llms.txt](https://go.sai.show/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://go.sai.show/part07.middleware/7.04-middlewareopentelemetry-zong-jie.md).

# 7.04 Middleware-OpenTelemetry总结

## PART1. 关联上游

![关联上游](/files/vf6pgXHdFOIYIrPkLap2)

记录span的Context要关联上请求中的span(`Context.Req.Context()`).

**如果你不知道该在span中记录什么标签,那你就去抄Kratos或go-zero或ego中的**

## PART2. 获取响应状态码

![获取响应状态码](https://github.com/step-by-step-wiki/GoBook/blob/main/img/16.Middleware-OpenTelemetry总结/获取响应状态码.png)

这里额外提一点,我们在span中记录的是请求命中的路由,而非请求的路径.这是因为路径中可能携带有多个路径参数,使得整个URL变得较为复杂

另外这里是因为我们无法从`http.ResponseWriter`直接获取响应状态码,只能是通过**将响应数据和响应码分别写入到`Context`的两个成员属性上,在执行完所有对响应码和响应数据的读写操作后(即返回相应之前),将响应数据和响应码刷到响应中**的方式,来获取响应数据和响应码.**相当于缓存了响应数据和响应码.等到所有的中间件都操作完了这份缓存的响应数据和响应码之后,返回响应之前,将它们刷到响应中**

![flashResp的执行时机](/files/19NLwkmw4TAS3tosmAB2)

TODO:可能我在AOP那一章节里对于中间件的组装顺序和执行顺序的解释是有误的,这个我需要确认


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