I think Jason is right in asking "why?". What do you want to achieve specifically with this behavior?
Varnish has streaming and request coalescing, meaning a request can be served as soon as data starts being available AND the backend doesn't suffer from simultaneous misses on the same object. I feel that should cover almost all your needs, so I'm curious about the use-case. On Dec 18, 2016 20:27, "Jason Price" <[email protected]> wrote: > It would be possible to do this with varnish... but I have to ask... why > bother? > > If the purpose is to offload the IO load, then varnish is good, but you > need to prime the cache... TBH, what I'd do first is put one or a pair of > varnish boxes really close to the overloaded box, and force all traffic to > that server through the close varnish boxes... using the do_stream feature, > you'll get stuff out there fairly quickly. > > After that is working nicely, I'd layer in the further out varnish boxes > which interact with the near-varnish boxes to get their data. > > This works well at scale since the local caches offer whatever's useful > local to them, and the 'near-varnish' boxes handle the 'global caching' > world. > > This was how I arranged it at $PreviousGig and the outer CDN was getting a > 85-90% cache hit ratio, and the inner tier was seeing 60% cache hit > ratio's. (The inner tier's ratio will depend heavily on how many outer > tier's there are...) > > On Sat, Dec 17, 2016 at 8:09 PM, Anton Berezhkov < > [email protected]> wrote: > >> This is how I semi-implemented: http://pastebin.com/drDP8JxP >> Now i need to use script which will run "curi -I -X PUT >> <url-to-put-into-cache>". >> >> >> > On Dec 18, 2016, at 3:58 AM, Mark Staudinger <[email protected]> >> wrote: >> > >> > Hi Anton, >> > >> > Have you looked into the "do_stream" feature of Varnish? This will >> begin serving the content to the visitor without waiting for the entire >> object to be downloaded and stored in cache. Set in vcl_backend_response. >> > >> > https://github.com/mattiasgeniar/varnish-4.0-configuration- >> templates/blob/master/default.vcl >> > >> > Cheers, >> > Mark >> > >> > On Sat, 17 Dec 2016 19:05:48 -0500, Anton Berezhkov < >> [email protected]> wrote: >> > >> >> Hello. >> >> >> >> Switched to Varnish from Nginx for additional functionality and better >> control of handling requests. >> >> But still can't implement what i want. And I want simple behaviour >> "Redirect on MISS/PASS". >> >> I want to use VC for deploying quick "cdn" servers for our >> mp4-video-servers (used for HTML5 players), without need to store all files >> on this quick (ssd, upto 2x480GB space, full database about 6TB). >> >> >> >> Currently we have 6 servers with SATA HDDs and hitting iowait like a >> trucks :) >> >> >> >> Examples: >> >> - Request -> Varnish -> HIT: serve it using Varnish. >> >> - Request -> Varnish -> MISS: start caching data from backend, and >> instantly reply to client: `Location: http://backend/$req.url"; >> >> - Request -> Varnish -> UPDATE: see `-> MISS` behaviour. >> >> >> >> From my perspective, i should do this "detach & reply redirect" >> somewhere in `vcl_miss` OR `vcl_backend_fetch`, because if i understood >> correctly https://www.varnish-cache.org/docs/4.1/reference/states.html, >> i need vcl_backend_response to keep run in background (as additional >> thread) while doing return(synth(...)) to redirect user. >> >> >> >> Similiar thing is "hitting stale content while object is updating". >> >> But in my case "replying redirect while object is updating". >> >> >> >> Also, i pray to implement this without writing additional scripts, >> why? I could do external php/ruby checker/cache-pusher with nginx & etc. >> But scared by performance downgrade :( >> >> _______________________________________________ >> >> varnish-misc mailing list >> >> [email protected] >> >> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc >> >> >> _______________________________________________ >> varnish-misc mailing list >> [email protected] >> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc >> > > > _______________________________________________ > varnish-misc mailing list > [email protected] > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc >
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