I think that conditional GETs could be really useful here. I just don't know how varnish works in this scenario. Maybe someone from the varnish development team can shed some light here :)
On Fri, Dec 17, 2010 at 12:42 PM, James A. Robinson < [email protected]> wrote: > On Thu, Dec 16, 2010 at 12:31, Paulo Paracatu <[email protected]> > wrote: > > If I understood it, the purging method isn't automatic, right? I'd need > to > > purge the content everytime it is modified. > > This is kinda stupid... I host more than 10k sites, modifying files > > everytime. If I set a high TTL, the backend will be happy and the > webmaster > > will be angry. If I set a low TTL, the webmaster will be happy, but the > > backend will die. Plus, there is no point using a cache if the TTL is > low. > > In a later post you ask about whether or not varnish could be > configured to send a conditional GET on every request > > Basically varnish would be looking up an item in its own cache, seeing > if it had a Last-Modified or ETag header from the backend, and sending > a conditional GET -- if it got an entity back it'd store that entity > as the new version, otherwise serve the old. I'd be curious if > anyone's put together VCL logic that is capable of that. It'd be good > to know how to do it. > > If it's possible to due, this technique might work well when you are > fronting a backend that is very fast at computing conditional GETs, > e.g., static files that can be examined to see if its inode, size, or > last modified time has changed. I imagine most people using varnish > have slower backend servers, ones that build dynamic content and > aren't able to respond to conditional GETs any more efficiently than > they could respond to an unqualified GET. > > One of the places we use varnish at my dept is fronting a large (half > terabyte of about six million files) static file server. Instead of > using some form of conditional GET, what we use are cache channels. > > http://tools.ietf.org/id/draft-nottingham-http-cache-channels-01.txt > > When various programs are updating the backend server static files > they POST the filepath to our cache channel server. We have another > program running that monitors the cache channel once a minute for > updates, and when it sees a new entry show up it turns around and > sends a PURGE request to varnish. > > Jim > > - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - > James A. Robinson [email protected] > Stanford University HighWire Press http://highwire.stanford.edu/ > +1 650 7237294 (Work) +1 650 7259335 (Fax) > > _______________________________________________ > varnish-misc mailing list > [email protected] > http://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc >
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