From e93a95d0cb92d91225bdf30abb8e661503fde6c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20W=C3=B3jcik?= <wojcikstefan@gmail.com>
Date: Sat, 25 Feb 2017 14:09:10 -0500
Subject: [PATCH] Test and document controlling the size of the connection pool
 (#1489)

---
 mongoengine/connection.py |  9 +++++++--
 tests/test_connection.py  | 29 +++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/mongoengine/connection.py b/mongoengine/connection.py
index c7c16ca3..7eae810f 100644
--- a/mongoengine/connection.py
+++ b/mongoengine/connection.py
@@ -51,7 +51,9 @@ def register_connection(alias, name=None, host=None, port=None,
         MONGODB-CR (MongoDB Challenge Response protocol) for older servers.
     :param is_mock: explicitly use mongomock for this connection
         (can also be done by using `mongomock://` as db host prefix)
-    :param kwargs: allow ad-hoc parameters to be passed into the pymongo driver
+    :param kwargs: ad-hoc parameters to be passed into the pymongo driver,
+        for example maxpoolsize, tz_aware, etc. See the documentation
+        for pymongo's `MongoClient` for a full list.
 
     .. versionchanged:: 0.10.6 - added mongomock support
     """
@@ -241,9 +243,12 @@ def connect(db=None, alias=DEFAULT_CONNECTION_NAME, **kwargs):
     running on the default port on localhost. If authentication is needed,
     provide username and password arguments as well.
 
-    Multiple databases are supported by using aliases.  Provide a separate
+    Multiple databases are supported by using aliases. Provide a separate
     `alias` to connect to a different instance of :program:`mongod`.
 
+    See the docstring for `register_connection` for more details about all
+    supported kwargs.
+
     .. versionchanged:: 0.6 - added multiple database support.
     """
     if alias not in _connections:
diff --git a/tests/test_connection.py b/tests/test_connection.py
index cc75f1e7..a1d3bfb6 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -285,8 +285,7 @@ class ConnectionTest(unittest.TestCase):
         self.assertTrue(isinstance(conn, pymongo.mongo_client.MongoClient))
 
     def test_connection_kwargs(self):
-        """Ensure that connection kwargs get passed to pymongo.
-        """
+        """Ensure that connection kwargs get passed to pymongo."""
         connect('mongoenginetest', alias='t1', tz_aware=True)
         conn = get_connection('t1')
 
@@ -296,6 +295,32 @@ class ConnectionTest(unittest.TestCase):
         conn = get_connection('t2')
         self.assertFalse(get_tz_awareness(conn))
 
+    def test_connection_pool_via_kwarg(self):
+        """Ensure we can specify a max connection pool size using
+        a connection kwarg.
+        """
+        # Use "max_pool_size" or "maxpoolsize" depending on PyMongo version
+        # (former was changed to the latter as described in
+        # https://jira.mongodb.org/browse/PYTHON-854).
+        # TODO remove once PyMongo < 3.0 support is dropped
+        if pymongo.version_tuple[0] >= 3:
+            pool_size_kwargs = {'maxpoolsize': 100}
+        else:
+            pool_size_kwargs = {'max_pool_size': 100}
+
+        conn = connect('mongoenginetest', alias='max_pool_size_via_kwarg', **pool_size_kwargs)
+        self.assertEqual(conn.max_pool_size, 100)
+
+    def test_connection_pool_via_uri(self):
+        """Ensure we can specify a max connection pool size using
+        an option in a connection URI.
+        """
+        if pymongo.version_tuple[0] == 2 and pymongo.version_tuple[1] < 9:
+            raise SkipTest('maxpoolsize as a URI option is only supported in PyMongo v2.9+')
+
+        conn = connect(host='mongodb://localhost/test?maxpoolsize=100', alias='max_pool_size_via_uri')
+        self.assertEqual(conn.max_pool_size, 100)
+
     def test_write_concern(self):
         """Ensure write concern can be specified in connect() via
         a kwarg or as part of the connection URI.