Hard to think of a reason why MongoDB doesn't create /data/db for us automatically?

Question

I installed MongoDB both on Win 7 and on Mac OS X, and both places, I got mongod (the server) and mongo (the client).

But at both places, running mongod will fail if I double click on the file, and the error message was gone too quickly before I can see anything. (was better on Mac because Terminal didn't exit automatically and showed the error message).

Turned out it was due to /data/db not exist and the QuickStart guide says: By default MongoDB will store data in /data/db, but it won't automatically create that directory

I just have a big question that MongoDB seems to want a lot of people using it (as do many other products), but why would it not automatically create the folder for you? If it didn't exist... creating it can do not much harm... especially you can state so in the user agreement. The question is why. I can think of one strange reason, but the reason may be too strange to list here...

Answer 1

One good reason would be that you do not want it in /data/db. In this case, you want it to fail with an error when you forgot to specify the correct directory on the command line. The same goes for mis-spelled directory names. If MongoDB just created a new directory and started to serve from there, that would not be very helpful. It would be quite confusing, because databases and collections are auto-created, so there would not even be errors when you try to access them.