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HTTP Headers

If-Match: <etag_value>
If-Match: <etag_value>, <etag_value>, …

If-None-Match: "<etag_value>"
If-None-Match: "<etag_value>", "<etag_value>", …
If-None-Match: *

If-Modified-Since: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT

If-Range: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT
If-Range: <etag>

If-Unmodified-Since: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT

Last-Modified: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT

ETag: W/"<etag_value>"
ETag: "<etag_value>"
  • Cache-Control, Content-Location, Date, ETag, Expires, Vary
  • https://www.rfc-editor.org/rfc/rfc9110#field.etag
  • https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers
  • end-to-end header
    • 应该从客户端一路传到最终后端
    • User-Agent, Accept
  • hop-by-hop header
    • 只对当前这一跳连接有效，代理不应该继续转发
    • Connection, Keep-Alive, Proxy-Authenticate, Proxy-Authorization, TE, Trailer, Transfer-Encoding, Upgrade
    • Connection 可以指定额外的 hop-by-hop header
      • Connection: X-Foo
      • 代理转发到后端前应该删除它