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On Thu, Jan 26, 2006 at 04:21:43PM +0100, Branko F. Gračnar wrote:
> Hellow ;)
>
> I found a nasty bug in ldirectord code, which led our lvs setup to work
> improperly - some http "real" servers were not checked becouse of "check
> caching" feature in ldirectord.
>
> I think, that this is a critical bug, which should be fixed immediately.
>
> This bug shows up in the following scenario in ldirector.cf:
>
>
> --- snip ---
> virtual=T.Z.U.P:80
> real=a.b.c.d:80 masq 1
> real=e.f.g.h:80 masq 1
> service=http
> virtualhost="www.domain1.tld"
> request="/testme.php?q=test"
> receive="success string"
> scheduler=lc
> persistent=600
> protocol=tcp
> checktype=negotiate
>
> virtual=T.Z.U.A:80
> real=a.b.c.d:80 masq
> real=e.f.g.h:80 masq
> service=http
> virtualhost="www.domain2.tld"
> request="/testme.php?q=test"
> receive="success string"
> scheduler=lc
> persistent=600
> protocol=tcp
> checktype=negotiate
>
> virtual=T.Z.U.S:80
> real=a.b.c.d:80 masq
> real=e.f.g.h:80 masq
> service=http
> virtualhost="www.domain3.tld"
> request="/testme.php?q=test"
> receive="success string"
> scheduler=lc
> persistent=600
> protocol=tcp
> checktype=negotiate
>
> virtual=T.Z.U.D:80
> real=a.b.c.d:80 masq
> real=e.f.g.h:80 masq
> service=http
> virtualhost="www.domain4.tld"
> request="/testme.php?q=test"
> receive="success string"
> scheduler=lc
> persistent=600
> protocol=tcp
> checktype=negotiate
> --- snip ---
>
> How to reproduce:
>
> Well, the bug shows up, when some real servers serve several different
> virtualhosts (in case of http lvs), and LVS virtual servers are configured
> almost identically.
>
> Ofcourse, this bug would not trigger if each and every lvs virtual server
> would have different "request" parameter.
>
> Impact: all real servers are added to lvs virtual servers, but not all are
> actually checked for proper operation (Already checked: real server= debug3
> message).
Thanks.
I think that a better fix would be to make the id_string of the virtual
include the virtualhost parameter. This way the caching could be shared
between virtual services. Actually, I think that if you make the
caching per-virtual then it should be removed, because I don't think
it will ever get a hit.
> Patch:
> Trivial patch is attached.
>
> Tested versions: 1.77.2.1 2004/04/20 05:05:29, 1.129 2006/01/15 16:25:19
>
> Best regards, Brane
> --- ldirectord.orig 2006-01-26 01:16:09.000000000 +0100
> +++ ldirectord 2006-01-26 01:17:09.000000000 +0100
> @@ -1475,8 +1475,8 @@
> {
> # Main failover checking code
> while (1) {
> - my @real_checked;
> foreach my $v (@VIRTUAL) {
> + my @real_checked;
> my $real = $$v{real};
> my $virtual_id = get_virtual_id_str($v);
>
--
Horms
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