bash script to start N docker containers, stop old versions, and update confd

gophercon.sh

#!/bin/bash
if [ -z "$1" ]
  then
    echo "usage : gophercon.sh 3 -- start three new instances"
	exit -1
fi

echo "Getting currently running gophercon containers"
OLDPORTS=( `docker ps | grep gophercon | awk '{print $1}'` )

echo "starting new containers"
for i in `seq 1 $1` ; do
echo "inside loop $1"
	JOB=`docker run -d -p 80 quay.io/bketelsen/gophercon | cut -c1-12`
	echo $JOB
	PORT=`docker inspect $JOB | grep HostPort | cut -d '"' -f 4 | head -1`
	curl http://127.0.0.1:4001/v2/keys/gophercon/upstream/$JOB -XPUT -d value="127.0.0.1:$PORT"
done

echo "removing old containers"
for i in ${OLDPORTS[@]}
do
	etcdctl rm /gophercon/upstream/$i
	confd -onetime
	docker kill $i
done

http://brianketelsen.com/2014/02/25/using-nginx-confd-and-docker-for-zero-downtime-web-updates/