HTTP notes

All about HTTP

Status code

204

• Status 204 代表的是「請求成功，但沒有 BODY」， 這個比較常用在 DELETE 操作

304 Not Modified

• There is no need to retransmit the requested resources.

This happens when:

1. the request method is a safe method, such as GET or HEAD
2. when the request is conditional and uses an If-None-Match or an If-Modified-Since header.

{
"header": {
  "If-None-Match": <e-tag>
  }
}

HTTP Header

X-HTTP-Method-Override

For some HTTP clients can only work with simple GET and POST requests. Use X-HTTP-Method-Override with a string value to contain PUT, PATCH, DELETE

X-Total-Count

• A count of the total number of Pagination count

E-tag

• The server gives client resources associated with E-tag

Next time, the client sends the same request with given E-tag, the server will use that E-tag to tell if it changes or not

• header: If-None-Match => if resource is not changed, status 304 not Modified => response quickly

Pros

• Fast response
• Less bandwidth
• Control consistency and concurrency

Cons

• Two servers behind load balancer may generate two E-tags (But it is configurable!)
• E-tag can be used to track users (e-tag is harder deleted than cookie)

References

1. HTTP Caching with E-Tags — (Explained by Example) — YouTube (2018)
2. 304 Not Modified HTTP Status (Explained with Code Example and Pros & Cons) — YouTube (2020)
3. https://chengr4.medium.com/restful-api-notes-3b3185391718
4. https://chengr4.medium.com/%E8%A8%88%E7%AE%97%E6%A9%9F%E7%B6%B2%E8%B7%AF%E5%92%8C%E7%B6%B2%E9%9A%9B%E7%B6%B2%E8%B7%AF-application-layer-7f77e3cdcdd1