Using low-bandwidth content during extreme load

ZXTM can automatically adapt what content is presented to users based on reaction to environmental conditions such as how busy a site is. In this example, ZXTM’s service level monitoring would be used to trigger off a change, without human intervention, to serve low-bandwidth versions of the content during periods of extreme load, to get more from the available resources.

A Service Level Monitoring Class monitors the response time for connections associated with the class, and can raise alerts if the service level falls below a configured response time and tolerance.

Select the "Classes" menu for the appropriate Virtual Server and then selecting Service Level Monitoring. Click "Create New Service Level Monitoring Class" and choose a name for your monitor.

Now set appropriate values for the following settings: -

Create a TrafficScript rule that uses the service level monitor and checks if the monitor is conforming. If the percentage of conforming responses is within tolerance, the default pool will be used. If the percentage of conforming responses drops below the tolerance level set, the low-bandwidth content pool will be used.

Add the following TrafficScript rule, as a request rule, to the appropriate virtual servers.

# Set the service level class to be used
connection.setServiceLevelClass( "LowResSLM" );

# Check if the service level class is conforming and
# select the appropriate pool to use based on the result
if( slm.isOK("LowResSLM") ) {
pool.use( "Web Site");
} else {
pool.use( "Low Res Pool" );
}

Graham Moore [Zeus Systems Engineering] 18 May 2006