Cluster monitoring via multiple htop instances

For cluster-usage monitoring I've mostly been using Ganglia, as covered here. But while it provides a great overview, sometimes you need to drill down and quickly see who's running what, on which node.

For this, htop is a great tool with minimal overheads - console friendly interface, tiny footprint etc.

I've put together a little script that allows the user to fire up multiple instances of htop, by opening multiple terminals with a 'ssh-and-run' combo that works well for me, so I thought I'd post it:

#!/bin/bash
ALL_HOSTS=(node1 node2 node3)

if [ $# == 0 ]; then
    TARGETS=("${ALL_HOSTS[@]}")
else
    echo '$0:' $0
    TARGETS=("$@")
fi

for HOST in "${TARGETS[@]}"; do
    gnome-terminal -t $HOST -e "ssh $HOST -t htop" &
done

Run with no arguments, this will open up 3 child terminals and connect to the nodes listed as ALL_HOSTS. Alternatively the user may supply a list of ssh targets as arguments. The tricky bit is the population and expansion of bash variable arrays - see http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_10_02.html for details.