Question about proxy cache when it expires
jerome at loyet.net
Wed May 20 16:32:39 MSD 2009
I'll try to look into the code to see what I can do. Do you have any
lead to guide me on this quest ? :)
2009/5/20 Igor Sysoev <is at rambler-co.ru>:
> On Tue, May 19, 2009 at 05:14:11PM +0200, J?r?me Loyet wrote:
>> > On Tue, May 12, 2009 at 10:38:04AM +0200, J?r?me Loyet wrote:
>> >> Hello igor,
>> >> I have a question about the cache behaviour in proxy mode.
>> >> I have nginx in front head which redirect to an apache back end. Nginx
>> >> caches eveything for M minutes.
>> >> If I have a large number of requests for the same page and this page
>> >> is cached : nginx returns the cached page ... no problems
>> >> After M minutes, the cached page expires
>> >> The first request coming after the expiration makes nginx to ask the
>> >> backend for refresh
>> >> When nginx receives the backend fresh response, it's saved to cache
>> >> and then nginx serves the fresh cached page
>> >> But what happen between the start of the request to the backend and
>> >> the end of the response from the backend ? (let's assume that the
>> >> backend serves the page in 5s ... and in 5s I can have a lot of
>> >> request to this page).:
>> >> - Are the request queued waiting for the backend response ?
>> >> - Every request makes try to refresh the cache from the backend ? (in
>> >> this case, I have multiple request for the same page to the backend
>> >> ... I can have a burst of request and my apache can be overflowed by
>> >> request -- that's why I'm using nignx with cache).
>> >> - Do the requests serve the cached page even if it's expired until the
>> >> backend response has been received ?
>> >> - Maybe something else :)
>> > Currently all requests which found that a cached response expired
>> > are proxied to backend. I plan to implement busy locks to pass the single
>> > request and leave others to wait the response up to specified time.
>> Hi igor,
>> about this feature. Do you know when you plan do implement it ? I
>> really need this feature. If you don't have enough time, I can look
>> into it if you explain to me briefly how you want to do it.
> This is complex thing that I plan to implement in 0.8.
> Igor Sysoev
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