[Seaside] Re: [squeak-dev] Upgrading running servers?
andreas.raab at gmx.de
Thu Apr 3 20:56:57 UTC 2008
Avi Bryant wrote:
> On Thu, Apr 3, 2008 at 12:00 PM, Stephen Pair <stephen at pairhome.net> wrote:
>> If I understand what DabbleDB does, they essentially give each user their
>> own squeak process to run in. When a session is first established, they
>> start up a new image. Upgrading would be a matter of dropping a new image
>> somewhere and as old sessions expire and new ones created, users are
>> migrated over to the new code. With hydraVM, a scheme like that might be
>> doable with just a small bit of session management in the main image.
> That's more or less right, yes. I've used variations on that strategy
> before - in general, having multiple images going where old sessions
> go to the old image but new sessions get routed to the new image makes
> for very smooth upgrades.
Yes, that's what we're doing too. When we need to upgrade a server we
simply don't let any new sessions go onto it and once everyone is off
the server is up for grabs. Unfortunately, some of the sessions last
quite a while (sometimes for several days because our notion of
"session" spans multiple users which need to overlap only for a short
amount of time) which I guess is good business-wise and we're not
running a lot of servers (which I guess is good too, since we scale) but
it makes for some rather long delays which could be mitigated by a "hot"
(or maybe just "warm") upgrade.
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