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Posted to dev@hc.apache.org by GitBox <gi...@apache.org> on 2020/08/18 10:27:41 UTC
[GitHub] [httpcomponents-client] dirkhenselin opened a new pull request #250: Avoid updating Content-Length header in a 304 response.
dirkhenselin opened a new pull request #250:
URL: https://github.com/apache/httpcomponents-client/pull/250
I observed the following problem: `Transfer-Encoding` and
`Content-Length` headers should be mutually exclusive and because I use
chunked transfer, the `Transfer-Encoding` header is set in the response
while the `Content-Length` header is not. In case of a 304 during a
revalidation, the header contains Content-Length=0. Probably a proxy is
responsible for this, just like the comment "Some well-known proxies
respond with Content-Length=0, when returning 304" in the method
CachedHttpResponseGenerator::addMissingContentLengthHeader is saying. In
CacheEntryUpdater::mergeHeaders the Content-Length=0 is merged into the
cached entry, but the cached entry contains also a `Transfer-Encoding`
header, so in the cached entry these headers aren't mutually exclusive
anymore. Because of the `Transfer-Encoding` header the method
CachedHttpResponseGenerator::addMissingContentLengthHeader isn't fixing
the `Content-Length` header and Content-Length=0 causes returning null
instead of the cached content. IMHO the `Content-Length` header should
not be merged into the cached response in case of a 304, at least if the
cached entry contains a `Transfer-Encoding` header.
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[GitHub] [httpcomponents-client] ok2c merged pull request #250: Avoid updating Content-Length header in a 304 response.
Posted by GitBox <gi...@apache.org>.
ok2c merged pull request #250:
URL: https://github.com/apache/httpcomponents-client/pull/250
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[GitHub] [httpcomponents-client] michael-o commented on pull request #250: Avoid updating Content-Length header in a 304 response.
Posted by GitBox <gi...@apache.org>.
michael-o commented on pull request #250:
URL: https://github.com/apache/httpcomponents-client/pull/250#issuecomment-675405532
Both headers seem to be pointless, RFC says:
```
The server generating a 304 response MUST generate any of the
following header fields that would have been sent in a 200 (OK)
response to the same request: Cache-Control, Content-Location, Date,
ETag, Expires, and Vary.
Since the goal of a 304 response is to minimize information transfer
when the recipient already has one or more cached representations, a
sender SHOULD NOT generate representation metadata other than the
above listed fields unless said metadata exists for the purpose of
guiding cache updates (e.g., Last-Modified might be useful if the
response does not have an ETag field).
```
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