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From Roeland Kuipers <RKuip...@schubergphilis.com>
Subject RE: HA redundant virtual router
Date Fri, 23 Aug 2013 08:56:16 GMT
Hi Sheng,

So far our testing showed no big problems. I've marked a redundant set of routers to be ha_enabled
by setting ha_enabled bit in the vm_instance table. (This is our workaround ATM)
We tested HA icw RvR in the scenarios ,shutdown / force power off VM. In these scenarios HA
worked a treat and did restore the redundant pair as it should. And keepalived nicely negotiated
MASTER & BACKUP.
These are obviously basic tests, but we are happy to do some more testing.

I understand your concerns and am totally in favour of the KISS principle. What could be the
scenario to end up with 3 routers? 
Why is the situation complex to deal with? These are separate mechanisms. HA just making sure
the router is up and alive. And keepalived negotatiating MASTER-BACUP states according to
keepalived configuration, unless there a 3 routers with conflicting configs. But so far I
do not understand the scenario where we could end up with 3 routers, so I cannot judge end/or
test this.

We like to see the hardcoded denial of HA in a redundant router setup go for several reasons:
1. It's counter intuitive - we configured an HA service offering on purpose for the RvR's.
And found out by accident that it was not enabled at all. 
2. CS could implement a default offering without HA for this setup (to keep it simple by default
and keep currently forced behaviour), but if users, like us, deliberately like to have HA,
users can create a custom offering with HA enabled

This way it's configurable, doesn't change default behavior and is more intuitive.

Thanks & Cheers,
Roeland



-----Original Message-----
From: Sheng Yang [mailto:sheng@yasker.org] 
Sent: vrijdag 23 augustus 2013 3:03
To: <dev@cloudstack.apache.org>
Subject: Re: HA redundant virtual router

It's a design choice, the only reason is it would be a very complex situation to deal with.
In fact the redundant router itself's policy has already been very complex...

We didn't look into details at the time of implementing redundant router, but there are lots
of concerns e.g. a network glitch may result in 3 routers running in the network and potentially
two of them are in MASTER state.

Of course discussion is welcome. We just want to keep it as simple as possible at the time.

--Sheng


On Thu, Aug 22, 2013 at 3:31 AM, Daan Hoogland <DHoogland@schubergphilis.com
> wrote:

> LS,
>
> Schuberg Philis guarantees 100% functional uptime for their customers.
> Infrastructure is of course part of this promise and the easier factor 
> to provide strong levels of resiliency. For this reason we want to 
> make use of redundant virtual routers together with HA functionality.
>
> We see HA and redundant routers as to different methods to provide 
> higher levels of uptime.
>
>
> 1.      The redundant router setup takes care of seamless failover without
> lengthy hick-ups in the case of a single router failure.
>
> 2.      HA takes care of restarting a failed VM or router. Restoring
> connectivity in the case of single router or restoring 2n resiliency 
> in the case of a redundant router setup.
>
> The combination of these two methods will help us to meet our 100% 
> promise; .We need to restore 2N redundancy ASAP in the case of single 
> component failure e.g. a router. With these two methods combined the 
> system is more autonomous and doesn't need human intervention to 
> restore redundancy.
>
> In the current situation we need to send a page to an on call engineer 
> to restore redundancy asap, because of the tight SLA's. While if we 
> could use HA icw redundant routers. The on-call guy can enjoy his 
> sleep and will be a more happy guy :) The present code forces the HA 
> offering to off on redundant routers which seems odd.
>
> So my question is: Why is it forced to off; Is there a technical 
> restraint or is this a design choice we can discuss and maybe revise?
>
> Cheers,
>
>

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