HP WebQoS Peak for HP-UX Concepts and Operation Guide

46 Chapter4
HP WebQoS Peak for the Zeus Web Server
Configuring HP WebQoS for Zeus
Each web server in a cluster listens for these broadcast messages. Based
on the messages received or not received, it will mark each system as up
or down.
The web server marks a system as up when it receives the appropriate
broadcast message from that system. The web server marks a system as
down when it receives the appropriate message or it fails to receive a
message after a specified number of broadcast intervals.
In the HP WebQoS
$ZEUSHOME /ns-config/https- server_name /config/hpac/config.ac
configuration file, you can configure how often messages are sent
(broadcast interval) and how many messages can be missed before the
system is marked as down. The parameters are:
cluster.keepalive.interval 60
cluster.keepalive.misses 3
where the interval is measured in seconds. The values given are the
default values.
If you configure these parameters, the web server must be restarted.
Also, all systems in the cluster should use the same values for these
parameters.
Decreasing the broadcast interval decreases the time it takes to detect a
failure. However, it also increases broadcast traffic.
Sometimes, not all broadcast messages are received. Therefore, the
number of misses should be set to a value greater than one. However, in
a large cluster, removing a machine falsely does not severely impact the
cluster’s capacity and improves the responsiveness to failures.
The maximum time to detect a failure can be determined by multiplying
the broadcast interval by the number of misses. For the default values,
the maximum failure detection time is three minutes.