Connections
We may connect to MongoDB by utilizing the mongoose.connect()
method.
mongoose.connect('mongodb://localhost/myapp');
This is the minimum needed to connect the myapp
database running locally on the default port (27017). We may also specify several more parameters in the uri
depending on your environment:
mongoose.connect('mongodb://username:password@host:port/database');
Options
The connect
method also accepts an options
object which will be passed on to the underlying driver.
mongoose.connect(uri, options);
The following option keys are available:
db - passed to the connection db instance
server - passed to the connection server instance(s)
replset - passed to the connection ReplSet instance
user - username for authentication (if not specified in uri)
pass - password for authentication (if not specified in uri)
See the driver for more information about available options.
Note: The server option auto_reconnect
is defaulted to true.
Note: The db option forceServerObjectId
is set to false and cannot be overridden.
ReplicaSet Connections
The same method is used to connect to a replica set but instead of passing a single uri
we pass a comma delimited list of uri
s.
mongoose.connect('mongodb://username:password@host:port/database,mongodb://username:password@host:port,mongodb://username:password@host:port' [, options]);
NOTE: The database
need only be specified in one of the uri
s.
Multiple connections
So far we've seen how to connect to MongoDB using Mongoose's default connection. At times we may need multiple connections open to Mongo, each with different read/write settings, or maybe just to different databases for example. In these cases we can utilize mongoose.createConnection()
which accepts all the arguments already discussed and returns a fresh connection for you.
var conn = mongoose.createConnection('uri,uri,uri...', options);
Connection pools
Each connection
, whether created with mongoose.connect
or mongoose.createConnection
are all backed by an internal configurable connection pool defaulting to a size of 5. Adjust the pool size using your connection options:
mongoose.createConnection(uri, { server: { poolSize: 10 }});
Next Up
Now that we've covered connections
, let's take a look at how we can break pieces of our functionality out into reusable and shareable plugins.