PYTHON-1156 - Note 3.0 MongoClient constructor change

Author: behackett

pymongo/mongo_client.py

@@ -125,6 +125,24 @@ def __init__(
 
  client = MongoClient('/tmp/mongodb-27017.sock')
 
+ .. note:: Starting with version 3.0 the :class:`MongoClient`
+ constructor no longer blocks while connecting to the server or
+ servers, and it no longer raises
+ :class:`~pymongo.errors.ConnectionFailure` if they are
+ unavailable, nor :class:`~pymongo.errors.ConfigurationError`
+ if the user's credentials are wrong. Instead, the constructor
+ returns immediately and launches the connection process on
+ background threads. You can check if the server is available
+ like this::
+
+ from pymongo.errors import ConnectionFailure
+ client = MongoClient()
+ try:
+ # The ismaster command is cheap and does not require auth.
+ client.admin.command('ismaster')
+ except ConnectionFailure:
+ print("Server not available")
+
  .. warning:: When using PyMongo in a multiprocessing context, please
  read :ref:`multiprocessing` first.