[Seaside] Re: Load balancing with one session per image
yanni at rogers.com
Tue Jun 23 05:25:24 UTC 2009
Bob Nemec wrote:
> How can we load balance across a number of VW Seaside images where we limit
> each image to one Seaside session? So, once a Seaside session is affiliated
> with a VW image, no other Seaside session can be serviced by that image.
> The image is only available when the session expires or the user logs out.
Here is an untested idea. If a request comes in without a session key,
then redirect the request to an assigner image that can assign a session
key and an affiliated worker image. Then another redirect would get the
load balancer to send the request to the right worker image.
If you're using GemStone (or even a relational DB), then a list of
available worker images could be kept. Each image would
register/unregister it's availability, by adding/removing itself to/from
the collection. Initially, the image's status would be session-is-free.
The assigner application would chose an available worker image, which
has image status: session-is-free. The assigner would change the status
to: session-is-assigned. Then the redirect is done to the assigned
When the session terminates, the worker image would update it's status
to: session-is-free - thus returning itself to the worker image pool.
Maybe you could have the assigner functionality run in every worker
image, instead of only in a single designated image. In this case, the
assigner code would need to test for session-is-free and set
session-is-assigned in a single transaction.
Hope this helps.
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