MongoDB, Java: accessing cursor opens connection that cannot be closed

Question

I have problem to close a connection that is always created after accessing the MongoDB cursor.

I am gathering the information about the connections from the console of the running mongod instance. I am not using any mongodb replication nor sharding yet.

For example a sample code causing an opened connection (assume 'myQuery' is just some query, coll is mapped using setInternalClass to the class MyObject):

  DBCursor find = coll.find(myQuery);
  List<MyObject> myObjects = new ArrayList<MyObject>();
  while(find.hasNext()) { // this line opens the connection
        MyObject next = (MyObject) find.next();
        myObjects.add(next);
  }
  find.close(); // this line will not close the connection

Answer 1

You are calling close on your find object, which is a DBCursor. As mentioned in the API Documentation this will close only the cursor, not the underlying connection. To close the connections you should call close on the Mongo/MongoClient object, which either inherits or has a close function that will as per the API close all connections to the MongoDB server instance.