Service Discovery for Docker to update PowerDNS MySQL

docker-powerdns-servicediscovery.sh

#!/bin/bash

# watch events until infinity
UNTIL=99999999999

# respect events 30sec in the past to not forget
# started containers AFTER "register running" but BEFORE event listener starts
SINCE=$(expr `date +%s` - 30)

DOMAIN=fubar
PDNS=powerdns

# clear oldrecords
docker exec $PDNS manage delrecord "$HOSTNAME-%"


# register all current running containers
docker ps -q \
| while read -r LINE
do
    CID=`docker inspect --format '{{ .Id }}' $LINE 2>/dev/null` || continue;
    NAME=`docker inspect --format '{{ .Name }}' $LINE 2>/dev/null` || continue;
    NAME=${NAME:1}
    IP=`docker inspect --format '{{ .NetworkSettings.IPAddress }}' $LINE`
    docker exec $PDNS manage addrecord $DOMAIN $NAME A $IP 60 $HOSTNAME-$CID
done


# start watching for events
docker events --since=$SINCE --until=$UNTIL \
| while read -r LINE
do
  if [[ ! $LINE =~ ^(.+)\ (.+):\ \(from\ (.+)\)\ (.+)$ ]] ; then
    echo no match: $LINE 
    continue;
  fi

  DATE="${BASH_REMATCH[1]}"
  CID="${BASH_REMATCH[2]}"
  EVENT="${BASH_REMATCH[4]}"


  # Container started
  if [ "$EVENT" = "start" ] ; then
    # be failor tolereant cause of --since
    NAME=`docker inspect --format '{{ .Name }}' $CID 2>/dev/null` || continue;
    NAME=${NAME:1}
    IP=`docker inspect --format '{{ .NetworkSettings.IPAddress }}' $CID`

    # skip container without name or ip
    if [ "$NAME" = "" ] || [ "$IP" = "" ] ; then
      continue;
    fi

    docker exec $PDNS manage addrecord $DOMAIN $NAME A $IP 60 $HOSTNAME-$CID
  fi


  # Container stopped
  if [ "$EVENT" = "die" ] ; then
    docker exec $PDNS manage delrecord $HOSTNAME-$CID
  fi

done