End user command caching

In a large system, users may tend to place excessive load on the system by manual or automated use of resource manager end user client commands. A simple way of reducing this load is through the use of client command wrappers which cache data. The example script below will cache the output of the command 'qstat -f' for 60 seconds and report this info to end users.

#!/bin/sh

# USAGE: qstat $@

CMDPATH=/usr/local/bin/qstat

CACHETIME=60

TMPFILE=/tmp/qstat.f.tmp

if [ "$1" != "-f" ] ; then

#echo "direct check (arg1=$1) "

$CMDPATH $1 $2 $3 $4

exit $?

if [ -n "$2" ] ; then

#echo "direct check (arg2=$2)"

$CMDPATH $1 $2 $3 $4

exit $?

if [ -f $TMPFILE ] ; then

TMPFILEMTIME=`stat -c %Z $TMPFILE`

else

TMPFILEMTIME=0

NOW=`date +%s`

AGE=$(($NOW - $TMPFILEMTIME))

#echo AGE=$AGE

for i in 1 2 3;do

if [ "$AGE" -gt $CACHETIME ] ; then

#echo "cache is stale "

if [ -f $TMPFILE.1 ] ; then

#echo someone else is updating cache

sleep 5

NOW=`date +%s`

TMPFILEMTIME=`stat -c %Z $TMPFILE`

AGE=$(($NOW - $TMPFILEMTIME))

else

break;

done

if [ -f $TMPFILE.1 ] ; then

#echo someone else is hung

rm $TMPFILE.1

if [ "$AGE" -gt $CACHETIME ] ; then

#echo updating cache

$CMDPATH -f > $TMPFILE.1

mv $TMPFILE.1 $TMPFILE

#echo "using cache"

cat $TMPFILE

exit 0

The above script can easily be modified to cache any command and any combination of arguments by changing one or more of the following attributes:

F.2 End user command caching