84
Chapter 4 Configuring Clusters
Using JRun probes
ClusterCATS provides load-balancing and failover support for your web applications in
two ways. First, it automatically interprets and reacts to the load metric that the JRun
servers generate. Second, ClusterCATS lets you create web application monitors. These
monitors can have multiple probes that periodically test the health and operation of the
websites that the JRun servers process.
Note:
Multiple JRun probes are allowed per web server, and JRun web applications can be
restarted individually. However, each web application should have only one probe that
restarts on a failure.
The probe is a high-availability feature that verifies that JRun servers are running
properly on clustered servers. It periodically tests specific JRun URLs at specified
intervals and verifies their validity against user-defined strings contained in the returned
pages.
If the validation test succeeds, inbound HTTP requests continue to be sent to the server
for which the probe exists. However, if a test fails (the URL fails, times out, or does not
return the user-specified string in the page accessed), ClusterCATS restricts that server
and redirects requests to other available servers in the cluster. ClusterCATS continues to
test the restricted server; when he probe returns a valid value, the server is considered
available.
If the JRun server hangs or fails, ClusterCATS attempts to recover the failed service.
When the JRun service is recovered, the probe can restart the JRun server and begin
sending HTTP traffic to it again.
This section describes the following:
•
“Configuring JRun probes in Windows” on page 84
•
“Configuring JRun probes in UNIX” on page 88
Configuring JRun probes in Windows
This section describes the following:
•
“Adding JRun probes” on page 84
•
“Removing JRun probes” on page 88
Adding JRun probes
ClusterCATS lets you set up one probe monitor for each server in a cluster. Each monitor
can have multiple probes associated with it. As a result, clusters typically have multiple
probe monitors (one for each server), and each monitor may have one or more probes.
The procedure for adding a new monitor and probe is different from adding a probe to a
server that already has a probe monitor. This section describes how to perform both
activities.
Note:
The JRun service must be running on your server to add a probe.
Summary of Contents for COLDFUSION MX-CLUSTERCATS
Page 1: ...macromedia Using ClusterCATS...
Page 56: ...46 Chapter 3 Installing ClusterCATS...
Page 118: ...108 Chapter 4 Configuring Clusters...
Page 156: ...146 Index...
