Speed up Varnish miss

AD straightflush at gmail.com
Tue Aug 30 13:56:33 CEST 2011


Does the browser need to support this explicitly?

On Tue, Aug 30, 2011 at 4:24 AM, Kristian Lyngstol <
kristian at varnish-software.com> wrote:

> On Mon, Aug 29, 2011 at 12:52:05PM -0400, Drew wrote:
> > A Varnish fetch to the back-end takes longer than not having varnish
> > at all. Is this normal and if so is there a way to speed up cache
> > misses?
>
> Like the others have pointed out, a bit of overhead is natural.
>
> However, there is one big factor here so far left unmentioned.
>
> Varnish, by default, will fetch an entire object before it starts
> sending it to the client. For a slow object (a large object fetched from
> a slow web server, for instance), this will add a significant delay.
>
> However, with Varnish 3.0.0, Varnish can stream these objects when there
> is a cache miss or a pass. That means Varnish will start sending the
> data to the client as the data arrives from the web server. This is not
> enabled by default, and requires beresp.do_stream = true;.
>
> Note that this doesn't apply to busy objects. In other words: if a
> client is already fetching an object, and an other client requests the
> same object, the first client will get the data on-the-fly, while the
> second client has to wait.
>
> Support for full streaming is work in progress and a working
> implementation exists, though it is not yet merged with the master
> branch.
>
> - Kristian
>
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