How to have eve write to different databases based on various URL parameters and request values?

Question

I'm attempting to create a REST API that selects the appropriate mongo database to write to along with the correct collection. How do I have eve select the database with the same name as a parameter as well as the collection?

Answer 1

With upcoming v0.6 Eve will natively support multiple Mongo instances.

New: Support for multiple MongoDB databases and/or servers.

You can have individual API endpoints served by different Mongo instances:

mongo_prefix resource setting allows overriding of the default MONGO prefix used when retrieving MongoDB settings from configuration. For example, set a resource mongo_prefix to MONGO2 to read/write from the database configured with that prefix in your settings file (MONGO2_HOST, MONGO2_DBNAME, etc.)

And/or you can use a different Mongo instance depending on the user hitting the database:

set_mongo_prefix() and get_mongo_prefix() have been added to BasicAuth class and derivates. These can be used to arbitrarily set the target database depending on the token/client performing the request.

A (very) naive implementation of user instances, taken from the docs:

from eve.auth import BasicAuth

class MyBasicAuth(BasicAuth):
    def check_auth(self, username, password, allowed_roles, resource, method):
        if username == 'user1':
            self.set_mongo_prefix('MONGO1')
        elif username == 'user2':
            self.set_mongo_prefix('MONGO2')
        else:
            # serve all other users from the default db.
            self.set_mongo_prefix(None)
        return username is not None and password == 'secret'

app = Eve(auth=MyBasicAuth)
app.run()

Also:

Database connections are cached in order to not to loose performance. Also, this change only affects the MongoDB engine, so extensions currently targeting other databases should not need updates (they will not inherit this feature however.)

Hope this will cover your needs. It's currently on the development branch so you can already experiment/play with it.

Answer 2

Say you have parameters "dbname" and "collectionname", and a global MongoClient instance named "client":

collection = client[dbname][collectionname]

PyMongo's client supports the "[]" syntax for getting a database with a given name, and PyMongo's database supports "[]" for getting a collection.

Here's a more complete example with Flask:

client = MongoClient()

@app.route('/<dbname>/<collection_name>')
def find_something(dbname, collection_name):
    return client[dbname][collection_name].find_one()

The good thing about my example is it reuses one MongoClient throughout, so you get optimal performance and connection pooling. The bad thing, of course, is you allow your users to access any database and any collection, so you'd want to secure that somehow.