To feed sge_execd with additional load information, you must supply a load sensor. The load sensor can be a script or a binary executable. In either case, the load sensor's handling of the standard input and standard output streams and its control flow must comply with the following rules:
The load sensor must be written as an infinite loop that waits at a certain point for input from STDIN.
If the string quit is read from STDIN, the load sensor is supposed to exit.
As soon as an end-of-line is read from STDIN, a retrieval cycle for loading data is supposed to start.
The load sensor then performs whatever operation is necessary to compute the desired load figures. At the end of the cycle, the load sensor writes the result to STDOUT.
If load retrieval takes a long time, the load measurement process can be started immediately after sending a load report. When quit is received, the load values are then available to be sent.
The format for the load sensor rules is as follows:
A load value report starts with a line that contains nothing but the word begin.
Individual load values are separated by newlines.
Each load value consists of three parts separated by colons (:) and contains no blanks.
The first part of a load value is either the name of the host for which load is reported or the special name global.
The second part of the load sensor is the symbolic name of the load value, as defined in the complex. See the complex(5) man page for details. If a load value is reported for which no entry in the complex exists, the reported load value is not used.
The third part of the load sensor is the measured load value. A load value report ends with a line that contains the word end.
The following example shows a load sensor. The load sensor is a Bourne shell script.
#!/bin/sh myhost=`uname -n` while [ 1 ]; do # wait for input read input result=$? if [ $result != 0 ]; then exit 1 fi if [ $input = quit ]; then exit 0 fi #send users logged in logins=`who | cut -f1 -d" " | sort | uniq | wc -l | sed "s/^ *//"` echo begin echo "$myhost:logins:$logins" echo end done # we never get here exit 0
Save this script to the file load.sh. Assign executable permission to the file with the chmod command. To test the script interactively from the command line, type load.sh and repeatedly press the Return key.
As soon as the procedure works, you can install it for any execution host. To install the procedure, configure the load sensor path as the load_sensor parameter for the cluster configuration, global configuration, or the host-specific configuration. See Basic Cluster Configuration or the sge_conf(5) man page for more information.
The corresponding QMON window might look like the following figure:
The reported load parameter logins is usable as soon as a corresponding attribute is added to the complex. The required definition might look like the last table entry shown in the following figure.