Connecting to multiple mongodb instances from djan

Question

I am using mongoengine with Django and within my project need to connect to two instances of MongoDB while serving single request. It works just fine if I use:

connect("mdb1")
#do stuff with mdb1
...
connect("mdb2")
#do stuff with mdb2

but I am wondering if that's a proper way of doing it.

Answer 1

I think there is no a proper way to do this. The example of Matt turns obligatory use an connection by Document type. If I want to use one document with many connections the example doesn't fit.

Answer 2

Multiple database support was added in MongoEngine 0.6

Demo using register_connection.

alias_lists = ['users-books-db', 'user-db', 'book-db'] # list of aliases
dbs = ['author-book-pairs', 'users', 'books'] # list of databases
for alias, db in zip(alias_lists, dbs):
    register_connection(alias, db)

class User(Document):
    name = StringField()
    meta = {"db_alias": "user-db"}

class Book(Document):
    name = StringField()
    meta = {"db_alias": "book-db"}

class AuthorBooks(Document):
    author = ReferenceField(User)
    book = ReferenceField(Book)
    meta = {"db_alias": "users-books-db"}

Answer 3

@Ricardo at the official documentation theres a section explaining context management (i.e switching databases using the same document: http://mongoengine-odm.readthedocs.org/en/latest/guide/connecting.html#context-managers). The following code will switch the class User, originally stored in users-db to the new database archive-user-db

from mongoengine.context_managers import switch_db

class User(Document):
     name = StringField()

     meta = {"db_alias": "user-db"}

with switch_db(User, 'archive-user-db') as User:
     User(name="Ross").save()  # Saves the 'archive-user-db'