Load object formats

This section discusses XML and non-XML custom load objects.

A custom load object file is an XML or plain text file that provides real-time information about the load of each resource.

Resources can constrain multiple properties only if you are using XML load objects.

When you configure Global Traffic Management to use load feedback based on an XML or non-XML load object, GTM periodically fetches a fresh load object using HTTP or HTTPS. By default, GTM fetches the load object every 30 seconds.

The load object must be accurate, timely, and available. If it is inaccurate, GTM cannot correctly balance the load. If it is untimely, that is, if the load data it reports is not up to date, load oscillations can occur because GTM is not able to detect the results of load balancing decisions it makes soon enough.

If for some reason the load object is unavailable, GTM continues to use the most recent load data it was able to fetch successfully. Examples of reasons why the load object is unavailable include HTTP GET failures, the script throwing an error, or the server refusing connections.

You must configure GTM to fetch a load object for each data center from a server you define. Use Control Center to configure one or more load servers for each data center by specifying the following information:
  • The name or IP address of the load server(s)
  • The relative URL of the load object
  • Whether to use HTTP or HTTPS to fetch a load object
It's acceptable if the load object contains load information for other data centers, as the extra information is ignored.