On 26/08/17 00:37, Alexander Lazarev wrote:
Hello guys!
I'm using squid as a reverse-proxy. And I can't understand how squid
decides when to check for fresh version of file from origin server.
It looks like for some documents it sends 'If-Modified-Since' or similar
headers and if it gets 304, it serves file from cache. And for some
documents it doesn't check for fresh version and always serves from cache. > I was testing that with curl without any additional headers.
Can some explain how that works or where I can read about that in
detail?
The HTTP specification RFC 723x series was re-written to be a lot more
easily understood, so those are probably the best place to read up about it.
The features you are asking about are covered in:
Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
<https://tools.ietf.org/html/rfc7232>
Hypertext Transfer Protocol (HTTP/1.1): Caching
<https://tools.ietf.org/html/rfc7234>
And is it possible to make squid always check for fresh version
before serving from cache?
It does when needed. The situation may be clearer after reading the above.
Amos
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