As I hinted yesterday I've tried to automate the deployment of a sharded MongoDB cluster in Amazon. It's unnecessarily difficult (rumor has it 10gen is doing something about it in the future) but it's doable with appropriate amount of persistence.

I occasionally post so called "one liners", shell commands that can be used to filter out some data I need. The main reason I do this is that I can later find this when I try to google for it. This will be my first one liner for MongoDB. Ok, so it is actually 3 related one liners.

If you need to find out if a shard is already part of your MongoDB cluster, try this:


MONGOS="ec2-54-228-106-184.eu-west-1.compute.amazonaws.com"
echo "db.shards.find()" | mongo $MONGOS/config | grep Shard4 | wc -l


The result will be either 1 or 0.

Now, if the shard exists, you might want to know a hostname and port number of one of the members of that replicaset: