[lvs-users] Persistent connections not persisting after failover

Christian Balzer chibi at gol.com
Wed Aug 20 07:46:34 BST 2008


On Wed, 20 Aug 2008 11:28:52 +1000 Simon Horman wrote:
> More precisely, the destinations are stored in a linked list.
> Insertions are always made at the end of the link list.
> Removals are done in place. The list is never reordered,
> other than through the effects of insertions and removals.
> It is the order of entries in the link list that determines
> what the hash table used like -SH looks like.
> So if the list is the same, the hash will be the same.
> Otherwise it won't be.
> If you are using something like ldirectord to monitor real-servers
> and add and remove them (not quiesce them), then its entirely
> likely that the order of the list will become inconsistent between
> two linux directors over time.
I suppose the majority of people are using ldirectord.
> If on the other hand you just run ipvsadm once on boot to set
> up the real servers, or your ldirectord-tool quiesces dead real servers,
> then the order of the list shouldn't change and should be consistent
> between two linux directors.
That would be sage advice if you actually COULD quiesce real servers with
SH. And I really hate to keep quoting myself here, but maybe one of these
days somebody with something resembling a clue might actually deem to
look at this and answer/fix it. ^_-

On the other hand (and I seriously don't want to come across as a fountain
of negative vibes, but I do realize I probably am) this problem is likely
to "fix" itself within the next 18 months when I will be forced to support
IPV6 and thus having to look for some other load balancing solution (and I
really really like IPVS, I seriously do).


Christian Balzer        Network/Systems Engineer                NOC
chibi at gol.com   	Global OnLine Japan/Fusion Network Services

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