Possible via a Perlbal plugin?

André Cruz andre.cruz at segula.pt
Wed Apr 18 14:55:43 UTC 2007

On Apr 18, 2007, at 3:44 PM, Brad Fitzpatrick wrote:

> Bot both uri hashing and sticky sessions come down to the basic  
> problem
> of:  what to do in subsequent requests when that old node is out of  
> the
> pool or down?  What are all the tunables for this policy/timeouts/etc?

In my situation, if the intended backend is not available then tough  
luck, ignore the preference and use the best available one. In the  
applications I have here the sticky sessions are needed purely for  
efficiency (a cache that is not replicated across all nodes).

I would like to be able to configure the sticky session trigger and  
timeout. Some applications require sticky sessions just to do some  
auth checks and don't need them afterwards...
A small configurable timeout to wait for the backend to come up would  
be nice, but not a must-have. If it's not up, what can you do?

> And in your case, how do requests waiting for a specific backend  
> compete
> for requests waiting for any backend?  Imagine 3*(n+1) queues, n per
> backend (high+normal+low priorities), then then high+normal+low  
> priorities
> for ANY backend.

Well... I guess clients that specify a backend should have precedence  
over others with the same priority but for any backend (since some  
kind of flow is already active), but I would be satisfied if they  
just received the same treatment as all the other requests.. But I  
don't prioritize requests here so I'm biased.

Hope this helps,
André Cruz

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