REPLICASETNAME="CMapsShard4"
MONGOS="ec2-54-228-106-184.eu-west-1.compute.amazonaws.com"
HOSTNAME=`/usr/bin/curl -s http://169.254.169.254/latest/meta-data/public-hostname`
PORT=27017

# This could be used to check if we are already member of a replicaset:
# echo "db.serverStatus().repl" | mongo
# Now we just assume we are not, and proceed to either intiate a new replicaset,
# or discover and join an existing one

for LOOPCOUNT in 1 2 3 4
do

# Find out if REPLICASETNAME is already registered with the mongos servers
FOUND=`echo "db.shards.find()" | mongo $MONGOS/config | grep $REPLICASETNAME | wc -l`

if [ $FOUND -gt 0 ]; then
  echo "Shard $REPLICASETNAME found. I will now proceed to add myself to it."
  # Find the first member of the replica set, then connect to it and add myself
  RSHOST=`echo "db.shards.find( { \"_id\" : \"$REPLICASETNAME\" }, { \"host\" : true, \"_id\" : false } )" | mongo $MONGOS/config | grep $REPLICASETNAME | awk -F":" '{ print $2}' | awk -F"/" '{print $2}'`  
  RSPORT=`echo "db.shards.find( { \"_id\" : \"$REPLICASETNAME\" }, { \"host\" : true, \"_id\" : false } )" | mongo $MONGOS/config | grep $REPLICASETNAME | awk -F":" '{ print $3}' | awk -F"," '{print $1}' | awk -F'"' '{print $1}'`
  echo "Found existing member of the shard: $RSHOST:$RSPORT. I will now connect to it."
  echo "rs.add('$HOSTNAME')" | mongo "$RSHOST:$RSPORT"
  exit 0
fi

# If the shard didn't exist yet, we are in for a ride. MongoDB sure doesn't make automated AWS deployment easy...
# Due to the way replicasets are initialized, we need to use our own locking mechanism
# to avoid race conditions with other nodes that might be doing this at the same time.
# (Basically, only one node can do the rs.initialize() and there's no easy way to undo
# it if 2 would do it at the same time.)
echo "Shard $REPLICASETNAME does not exist yet. I will now try to get the lock to initialize replica set."

# This will throw "norepl" error. This is ok, it's because we are writing to the config nodes
echo "db.deployment.locks.insert( { _id : \"$REPLICASETNAME\", locked: true, owner: \"$HOSTNAME:$PORT\" } )" | mongo $MONGOS/config
# Now check if we got the lock or not
# Note that if someone else already inserted the same lock, then our above insert failed
HAVE_LOCK=`echo "db.deployment.locks.find( { _id : \"$REPLICASETNAME\", locked : true, owner : \"$HOSTNAME:$PORT\" } ).count()" | mongo --quiet $MONGOS/config`



if [ $HAVE_LOCK -gt 0 ]; then
  echo "Got the lock. Now initializing replica set..."
  # We need to use this to use the public $HOSTNAME from above. By default rs.initiate() uses `hostname`
  cat <<EOF > /tmp/replicaSetConfigInit.js
config = {_id: "$REPLICASETNAME", members : [
  {_id : 0, host:"$HOSTNAME:$PORT"},
]};
rs.initiate(config);
EOF
  mongo /tmp/replicaSetConfigInit.js
  
  echo "The ReplicaSet is still configuring itself. Sleep 60 sec before proceeding"
  sleep 60
  # Add myself as the first member of this shard
  mongo --eval "sh.addShard('$REPLICASETNAME/$HOSTNAME')" $MONGOS
  
  # Release the lock (just cleanup, nobody should ever need it again
  echo "db.deployment.locks.remove( { _id : \"$REPLICASETNAME\" } )" | mongo $MONGOS/config

  exit 0
fi

# Someone else has the lock and is hopefully doing rs.initialize(). 
# All we can do is wait and start from the beginning.
echo "Someone else is holding the lock to do rs.initialize(). I will sleep 120 seconds and then retry to join the shard."
sleep 120

done