Run a command on all instances attached to an AWS ELB

elb.sh

#!/bin/bash


# Runs a command on all instances attached to a load balancer
# Elastic Load Balancer Tools from http://aws.amazon.com/developertools/2536

ELB=prod-axs-aeg
COMMAND='service varnish restart'
INSTANCES=$(elb-describe-instance-health $ELB | awk -F " " '{print $2}')

for INSTANCEID in ${INSTANCES} ; do
  INSTANCEURL=$(ec2-describe-instances $INSTANCEID | egrep '^INSTANCE' | awk -F " " '{print $4}')
  $SSH -l root $INSTANCEURL $COMMAND
done