While this is a very nifty bit of code, I'd be very careful about using it for unit testing as there is a high likelihood of minor behavior differences verses a real mongod which can cause surprises in production.

Also, for anyone looking to embed MongoDB and who doesn't mind using C++ it is possible and rather easy. In fact some of our unit tests and all of our tools other than the shell already do this. See https://github.com/mongodb/mongo/blob/master/tools/tool.cpp#... for the details. The DBDirectClient class implements the full C++ driver interface but does all operations in-process. The downside is that unlike when using our drivers (which have no licensing impact on your code) when you embed mongodb within your application it becomes bound by AGPL.

PS- That is really impressive for a weekend project! You should get in touch with us at 10gen if you're looking for a new job.

> While this is a very nifty bit of code, I'd be very careful about using it for unit testing as there is a high likelihood of minor behavior differences verses a real mongod which can cause surprises in production.

Yep, that's a valid point. My plan is to run my tests most of the time with embedded-mongo, and run against real mongo on occasion (such as say, using embedded-mongo while developing locally and real mongo before pushing to production). I haven't benchmarked it yet, but my test suite seems to run a lot faster with embedded-mongo than real mongo. And it's definitely a lot less work to use than an ad-hoc mock layer.

> PS- That is really impressive for a weekend project! You should get in touch with us at 10gen if you're looking for a new job.

Thanks! If my current startup goes down in flames, I'll be sure to give you a call :).

One really nice part about the implementation was I could just reuse the Ruby Mongo driver's test suite.

Interesting. So now I can test my mongodb app, without needing to install mongodb server on my machine? Cool!

Looks great! But the stinger is in the tail : "I think the next thing to add is indexes. Currently everything works via a linear scan of the database."

It depends on what you use it for. Without indexes, it could be used for testing without setting up a local MongoDB server, as long as there aren't too many records.

Thanks. Re: indexes - patches welcome :). I don't expect them to be hard to build though. Since embedded-mongo is in memory, they're just a bunch of hash tables.

In that case, I would think that the indexing stuff (i.e. hash lookups) would be way better than linear already. Cool.

This seems really fun. I'd love to be able to use this almost like a version of SQLlite, but a JSON interface. I could see this in Android/iPhone, as well as Desktop apps.

CouchDB already has embeddable ports to Android and iOS, and it has the added benefit of a built in master-slave or multiple-master replication system, so you can have your app get and push up to date data from a server when a connection is available, but still be fully functional without it, for free!

Embedded MongoDB on Android would be awesome.