On Thu, 2 Sep 2010, Graham Leggett wrote:
<snip>
Should however the cache implementation want to take a breath, it returns to
mod_cache with unconsumed bucket(s) still remaining in the "in" brigade.
mod_cache in turn sends the already-processed buckets in the "out" brigade
down the filter stack to the client, and then loops round, calling the
store_body() function again until the "in" brigade is empty.
In this way, the cache implementation has the option to swallow data in as
many smaller chunks as it sees fit, and in turn the client gets fed data
often enough to not get bored and time out if the file is very large.
Regards,
Graham
This could even go a bit further with providing the cache
implementation with a hint of when it would be polite of it to return.
I think it would probably be easier if the cache implementation knows
what's expected of it. Or?
Also, if the client hangs up, will the cache impl get the chance to
finish its job (ie. completing the caching of a file instead of
starting over later on)?
A side-step from this, how would it interact with the thundering herd
lock and slow client first to access large file while other fast
clients also wants to access it? Wouldn't this just be another variety
of the "client gets bored before reply" scenario?
Regarding the issue of the disk cache cramming the entire file into
memory/address space, an alternate solution could be that the cache
returns buckets pointing to the cached file, ie that the cache
consumed those pesky mmapped buckets. This way the cache could cache
the file rather quickly independent of the speed of the client, so
that the file caching is finished in a sane time so others can benefit
from it even though the cache-initiating request is running at
snail-speed...
/Nikke
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Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se | ni...@acc.umu.se
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"I'm going to hell. It's that simple. I am going straight to hell." - Veronica
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