User Guide

268 Chapter 12 Configuring ColdFusion Clusters
Server Load Thresholds
ClusterCATS makes certain that your Web applications remain available and running
at optimum performance by intelligently managing the amount of HTTP traffic
hitting your clustered servers. By setting load thresholds on each server in your
cluster, you can control and manage your site’s availability and performance. Many
of your threshold configuration decisions hinge on your site’s architecture and where
the bulk of your processing resources need to be allocated.
During an HTTP redirection, ClusterCATS evaluates the cluster’s state according to
HTTP server state first, and then ColdFusion server load. This policy is the same in
both centralized and distributed ClusterCATS configurations. In a centralized
ClusterCATS cluster with all Web servers at one site, ClusterCATS only redirects if the
server is busy or restricted.
For each cluster member, you configure two load thresholds:
• Peak load threshold The peak load threshold represents the maximum load the
server can handle before its performance degrades significantly or becomes
unavailable.
• Gradual redirection threshold The gradual redirection threshold represents the
point at which HTTP requests begin to be redirected to other less loaded
members in a cluster so that the server’s performance does not degrade or
become unavailable.
By default, the Peak load threshold is 90% and the gradual redirection threshold is
10%. These default settings adequately handle HTTP traffic going across most Web
sites. However, if your Web site is particularly processing intensive, you should lower
both threshold settings to better accommodate the increased load.
If you want the server to be able to handle as much load as possible, set both
threshold values close to one another. However, if you want redirection to occur well
in advance of the server nearing its peak threshold, set the values farther apart so
that there is a differential of at least 10% between the two threshold values.
This section shows you how to set the peak and gradual redirection load thresholds
for ClusterCATS servers in the following sections:
• “Configuring load thresholds in Windows” on page 268
• “Configuring load thresholds on UNIX” on page 272
Configuring load thresholds in Windows
To adjust load thresholds for a cluster member:
1 Open the ClusterCATS Explorer and select a server.
2Select Server > Properties. Alternatively, you can right-click the server and select
Properties.