MongoDB sharding by collection

Question

I have an application which creates a collection in MongoDB for every user where a collection is expected to have at most 100,000 documents (a few "big" users are like this while many "small" users only have less than 10,000 documents). Now the number of users grows and I want to shard my database. Is it possible to say "put this collection (thus this user) on this shard and that collection on that shard, but do not shard documents inside a collection further", and is it possible to do this automatically?

Edit: I'm already aware of MongoDB's standard sharding design now, but my application was scaled up from a small application for single person's use, where a nedb datastore is created for the user. When the multi-user support was added, it was an obvious choice to create a nedb datastore for every user so many parts of my application could stay unchanged. When I migrated it to MongoDB, since one nedb datastore is the equivalent of a MongoDB collection, I was using one collection per user. Given the current situation, I wonder the quickest way (~= with the smallest change to my application and overall configurations) to solve the current performance issue.

Answer 1

Sharding is done on a collection and how the sharded collection is broken up is based on the shard key (where one or more object elements from your collection make up the key).

It might be better to rethink your document design. You could have all users in one collection and then use the user id as the shard key . That would shard each user as a whole and do it automatically.

See Mongodb's Sharding documentation for more information on sharding.