Hi Tariq
Am 18.05.2006 um 12:28 schrieb Tariq Rashid:
So we could place the IMAP proxies closer to the webmail servers -
before the load balancers. This means that each webmail server must
be preconfigured to talk to a single IMAP proxy. This way the
persisted sessions survive through the load-balancers and only one
session is maintained to the backend real IMAP servers. However,
the problem with this is that there is reduced resilience - if the
proxy fails then no users can use that particular webmail server.
(user) ----- [webmail] -- -- -- [IMAP Proxy] -------- <lb> ------
[IMAP server]
What are people's opinions here? Are there any magic load-balancing
mechanisms that can be used to good effect here? The load-balancers
are Foundry ServerIron machines.
We are using exactly this design. Webmail and IMAP Proxy are on the
same physical maschine. Our experience is that it works quite well
and fast. But as you mentioned, there arise problems if the IMAP
Server is not reachable (when the loadbalancer has errors or IMAP
server is down). Then imapproxy startup will fail and therefore also
no webmail login is possible. So we coded a shell script as
workaround which checks if imapproxy is running. If not, startup the
proxy. The same problem arise if you got a power outage and the imap
proxy server are starting faster than the loadbalancers or imap servers.
Kind regards, Norbert
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