Re: ovf scheduler

To: Simon Horman <horms@xxxxxxxxxxxx>
Subject: Re: ovf scheduler
Cc: Julian Anastasov <ja@xxxxxx>, lvs-devel@xxxxxxxxxxxxxxx
From: "rhadoo.io88" <rhadoo.io88@xxxxxxxxx>
Date: Tue, 14 Jul 2015 17:29:15 +0300
Yes....adding thresholds support in ldirectord seems like a good ideea anyway...
But perhaps there would be benefit in merging my proposed OVF
scheduler with the existing FO, in essence they do the same thing but
matching the number of active connections supported by the node with
the node's weight whilst still keeping thresholds for the total number
of connections might give a bit more flexibility.

On Tue, Jul 14, 2015 at 4:36 AM, Simon Horman <horms@xxxxxxxxxxxx> wrote:
> Hi,
> On Tue, Jul 14, 2015 at 01:47:16AM +0300, rhadoo.io88 wrote:
>> Unfortunately i was not aware of the FO scheduler, i looked it up just
>> now...indeed you could get similar behavior with FO scheduler and
>> proper thresholds.
>> The only trouble with that is that i can't set the thresholds from
>> within ldirectord , so i won't be able to keep all the config in one
>> place,  and that upper threshold seems to take into account all
>> connections ( active and inactive) , that making the upper limit a bit
>> vague.
> Perhaps ldirectord could be enhanced in this regard?
>> i think this approach has the advantage of keeping all the config in
>> one place, having the weight set at the actual number of active
>> connections the node can handle whilst still allowing to have
>> thresholds on the total connections.
>> On Mon, Jul 13, 2015 at 11:35 PM, Julian Anastasov <ja@xxxxxx> wrote:
>> >
>> >         Hello,
>> >
>> > On Mon, 13 Jul 2015, rhadoo.io88 wrote:
>> >
>> >> Hi,
>> >> My name is Raducu Deaconu, i am a romanian syadmin/solution manager
>> >> and i have been working with lvs for some years now, great software!
>> >> I mainly use ldirectord on top of lvs and every now and then i do run
>> >> into customer tasks that would need new features.
>> >> One such feature is the need of a failover scheduler that would allow
>> >> a certain number of active connections to be served by a server and
>> >> only in case that is overloaded send some jobs to another/other
>> >> servers.
>> >> That would be needed say in the case you have let's say a galera
>> >> cluster and you want to make sure all writes go to one node, and only
>> >> one node,or in the case where you have some caching implemented in an
>> >> application and you want the virtual service to always go to that
>> >> server, unless there is a problem, case when another server can handle
>> >> the job, although without the caching.
>> >> These features are not possible now in ldirectord/lvs and i think they
>> >> would bring some benefits to many use cases like my own.
>> >
>> >         Can the same be achieved by setting --u-threshold
>> > and using the FO scheduler? ip_vs_bind_dest() sets the
>> > IP_VS_DEST_F_OVERLOAD flag if number of connections
>> > exceed upper threshold and then the FO scheduler can select
>> > another real server with lower weight.
>> >
>> > Regards
>> >
>> > --
>> > Julian Anastasov <ja@xxxxxx>
>> --
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