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From Mauro Vanetti <ma...@funambol.com>
Subject [users@httpd] Load balancing: nothing gets logged for a few seconds when a machine is rebooted
Date Wed, 12 May 2010 11:00:43 GMT
Hello!
I'm testing load balancing between four nodes placed in two distinct 
machines (2 + 2). The load balancer is on the first machine, where nodes 
11 and 12 are. Nodes 21 and 22 are on the second machine.
When I reboot the second machine, the load balancer detects the error 
and redirects all new requests to nodes 11 and 12 only, until the nodes 
on the second machine are up again.
This is all very good, the only problem is what happens in the critical 
seconds. Clearly, a few sessions will fail (those already started but 
not yet finished on nodes 21 and 22 when the second machine is 
rebooted). When this happens, the log shows that for 1-2 seconds no 
requests are managed (including those on the first machine!).
This goes to the point that even if I launch an automated ping (10x a 
second) on the first machine, the pinging is not logged during the 
critical seconds.

Real example (requests per second logged in access_log):
100
112
102
92
32 <-- CRISIS
0 <-- PEAK OF THE CRISIS
3 <-- CRISIS
25 <-- CRISIS
55 <-- RECOVERY
98
93
101

What can be the reason for this behaviour?
Thank you very much for your help. Best regards!
-- 
_____________ ________ _____ ___ __ _ _

Mauro Vanetti :: Pavia
_____________ ________ _____ ___ __ _ _

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