On Fri, May 19, 2006 at 12:22:02PM +0100, Tariq Rashid wrote:
> (user) ----- [webmail] -- -- -- <lb> -- -- -- [IMAP Proxy] -------- [IMAP
> server]
> \-- -- -- [IMAP Proxy] -------- [IMAP
> server]
> \-- -- -- [IMAP Proxy] -------- [IMAP
> server
>
> That is - load-balancers will spray start-do-stop sessions generated by each
> IMAP webmail page click. This means a single end user will have sessions
> across many backend IMAP servers unecessarily. The solution to this problem
> is to only push persisted long-term IMAP sessions over a load-balancer.
>
> (user) ----- [webmail] -- -- -- [IMAP Proxy] -------- <lb> ------ [IMAP
> server]
>
> \- no resilience -/
Alternatively:
(user) ------ <lb> ----- [webmail] - [IMAP Proxy] ---- <lb> ---- [IMAP server]
\---- [webmail] - [IMAP Proxy] -/ \--- [IMAP server]
\---- [webmail] - [IMAP Proxy] -/ \--- [IMAP server]
That is, use 'sticky' loadbalancing to ensure a particular user's HTTP
requests always hit the same webmail frontend. Each webmail frontend has its
own IMAP proxy (running on the same box).
Regards,
Brian.
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