Hi, Ken.
Ken Brownfield wrote:
> You could have the hash backends each be individual round/random
> directors with your intended server having a very high weight
> and your intended backup backend a weight of 1. Awkward and
> somewhat lengthy, but it works. The only downside is that the
> fallback will get a non-zero amount of traffic.
> director server1d random {
> { .backend = server1; .weight = 10000000; }
> { .backend = fallback1; .weight = 1; }
> }
I'm not sure I got your idea correctly as "hash backend" is not something I'm
aware of. Are you suggesting I cut-up the distribution manually?
I guess what I'm really after is a CARP[1] implementation such as the one in
F5's BigIP [2]. In their implementation the sick servers are removed from the
pool and the hash algorithm does its thing, redistributing the URLs amongst the
healthy servers.
The other way I understood your suggestion was to do something like this:
director R_director random {
{ .backend = centre_rail_ausyd_fap01; .weight = 1; }
(...)
{ .backend = centre_rail_ausyd_fap08; .weight = 1; }
}
director H_director hash {
{ .backend = centre_rail_ausyd_fap01; }
(...)
{ .backend = centre_rail_ausyd_fap08; }
}
director example random {
{ .backend = H_centre_rails; .weight = 999999; }
{ .backend = R_centre_rails; .weight = 1; }
}
That could work but varnish 2.1 doesn't take directors in .backend.
I'm trying to avoid using our BigIP to do the job because Varnish is currently
responsible for figuring-out the correct backend based on the request. If I
use the BigIP for this I'll need to either get rid of Varnish altogether add
another BigIP VIP to select the backend based on CARP (BigIP-PublicVIP ->
Varnish -> BigIP-InternalVIP -> Backends).
[1] http://en.wikipedia.org/wiki/Cache_Array_Routing_Protocol
[2] http://support.f5.com/kb/en-us/solutions/public/11000/300/sol11362.html
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