API for Agent Based Adaptive Balancing

1 API for Agent Based Adaptive Balancing

For adaptive scheduling, the LoadMaster periodically checks the system load on all servers in the farm. Each server machine has to provide a file that contains a numeric value in the range between 0 and 102 representing the actual load on this server (0 = idle, 99 = overload, 101 = server down, 102 = administratively disabled). The LoadMaster retrieves this file via an HTTP GET operation. It is the servers’ job to provide the actual load in the ASCII file. There are no prerequisites, though, to how the servers evaluate this information.

There are some conditions that must hold:

An ASCII file must exist with a number between 0 and 99 in the first line

The file must be accessible to an HTTP GET operation from the LoadMaster

The URL must be the same on all servers

The URL must match the Adaptive URL as set in Rules & Checking > Check Parameters

For further information on the Agent Based Adaptive Balancing, please refer to the link for MS Windows Adaptive Agent at http://kemptechnologies.com/documentation.

The lmperfagent file needs to be translated to the same language as the host operating system.

The following is an example script to determine and present the load information on a LINUX server:

Technical_Note-API_for_Agent_Based_Adaptive_Balancing_1_1.png

Here is an example of a C program to determine and present the load information on a MS Windows NT or 2000 server:

Technical_Note-API_for_Agent_Based_Adaptive_Balancing_1_2.png

This example code is a program that obtains the CPU load counter from Windows 2000. It uses the Performance Data Helper (PDH) API, and must be linked to the pdh.lib.

The PDH Dynamic Link Library (DLL) pdh.dll must also be installed on the system.

The counter paths for Windows 2000 must be modified dependent on the installed language.

References

Unless otherwise specified, the following documents can be found at http://kemptechnologies.com/documentation.

Web User Interface (WUI), Configuration Guide
Technical Note, Install Adaptive Agent - Windows
KEMP LoadMaster, Product Overview

Last Updated Date

This document was last updated on 12 October 2017.

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