Hi Daan,
In my opinion the biggest issue is the fact that there are a lot of different
code paths: VPC versus non-VPC, VPC versus redundant-VPC, etc. That's why you
cannot simply switch from a single VPC to a redundant VPC for example.
For SBP, we mitigated that in Cosmic by converting all non-VPCs to a VPC with a
single tier and made sure all features are supported. Next we merged the single
and redundant VPC code paths. The idea here is that redundancy or not should
only be a difference in the number of routers. Code should be the same. A
single router, is also "master" but there just is no "backup".
That simplifies things A LOT, as keepalived is now the master of the whole
thing. No more assigning ip addresses in Python, but leave that to keepalived
instead. Lots of code deleted. Easier to maintain, way more stable. We just
released Cosmic 6 that has this feature and are now rolling it out in
production. Looking good so far. This change unlocks a lot of possibilities,
like live upgrading from a single VPC to a redundant one (and back). In the
end, if the redundant VPC is rock solid, you most likely don't even want single
VPCs any more. But that will come.
As I said, we're rolling this out as we speak. In a few weeks when everything
is upgraded I can share what we learned and how well it works. CloudStack could
use a similar approach.
Kind Regards,
Remi
On 05/02/2018, 16:44, "Daan Hoogland" <daan.hoogl...@gmail.com> wrote:
H devs,
I have recently (re-)submitted two PRs, one by Wei [1] and one by Remi [2],
that reduce downtime for redundant routers and redundant VPCs respectively.
(please review those)
Now from customers we hear that they also want to reduce downtime for
regular VRs so as we discussed this we came to two possible solutions that
we want to implement one of:
1. start and configure a new router before destroying the old one and then
as a last minute action stop the old one.
2. make all routers start up redundancy services but for regular routers
start only one until an upgrade is required at which time a new, second
router can be started before killing the old one.
obviously both solutions have their merits, so I want to have your input
to make the broadest supported implementation.
-1 means there will be an overlap or a small delay and interruption of
service.
+1 It can be argued, "they got what they payed for".
-2 means a overhead in memory usage by the router by the extra services
running on it.
+2 the number of router-varieties will be further reduced.
-1&-2 We have to deal with potentially large upgrade steps from way before
the cloudstack era even and might be stuck to 1 because of that, needing to
hack around it. Any dealing with older VRs, pre 4.5 and especially pre 4.0
will be hard.
I am not cross posting though this might be one of these occasions where it
is appropriate to include users@. Just my puristic inhibitions.
Of course I have preferences but can you share your thoughts, please?
And don't forget to review Wei's [1] and Remi's [2] work please.
[1] https://github.com/apache/cloudstack/pull/2435
[2] https://github.com/apache/cloudstack/pull/2436
--
Daan
