PYTHON-2121 add directConnection URI option

Author: prashantmital

doc/changelog.rst

@@ -12,6 +12,8 @@ Version 3.11 adds support for MongoDB 4.4. Highlights include:
   support. It will also be installed when using the "tls" extra if the
   version of Python in use is older than 2.7.9.
 - Support for the :ref:`MONGODB-AWS` authentication mechanism.
+- Support for the ``directConnection`` URI option and kwarg to
+  :class:`~pymongo.mongo_client.MongoClient`.
 - Added index hinting support to the
   :meth:`~pymongo.collection.Collection.replace_one`,
   :meth:`~pymongo.collection.Collection.update_one`,

pymongo/client_options.py

@@ -151,6 +151,7 @@ def __init__(self, username, password, database, options):
         self.__codec_options = _parse_codec_options(options)
         self.__credentials = _parse_credentials(
             username, password, database, options)
+        self.__direct_connection = options.get('directconnection')
         self.__local_threshold_ms = options.get(
             'localthresholdms', common.LOCAL_THRESHOLD_MS)
         # self.__server_selection_timeout is in seconds. Must use full name for
@@ -191,6 +192,11 @@ def credentials(self):
         """A :class:`~pymongo.auth.MongoCredentials` instance or None."""
         return self.__credentials
 
+    @property
+    def direct_connection(self):
+        """Whether to connect to the deployment in 'Single' topology."""
+        return self.__direct_connection
+
     @property
     def local_threshold_ms(self):
         """The local threshold for this instance."""

pymongo/common.py

@@ -594,6 +594,7 @@ def validate_tzinfo(dummy, value):
     'authsource': validate_string,
     'compressors': validate_compressors,
     'connecttimeoutms': validate_timeout_or_none,
+    'directconnection': validate_boolean_or_string,
     'heartbeatfrequencyms': validate_timeout_or_none,
     'journal': validate_boolean_or_string,
     'localthresholdms': validate_positive_float_or_zero,

pymongo/mongo_client.py

@@ -205,6 +205,12 @@ def __init__(
           - `connect` (optional): if ``True`` (the default), immediately
             begin connecting to MongoDB in the background. Otherwise connect
             on the first operation.
+          - `directConnection` (optional): if ``True``, forces this client to
+             connect directly to the specified MongoDB host as a standalone.
+             If ``false``, the client connects to the entire replica set of
+             which the given MongoDB host(s) is a part. If this is ``True``
+             and a mongodb+srv:// URI or a URI containing multiple seeds is
+             provided, an exception will be raised.
 
           | **Other optional parameters can be passed as keyword arguments:**
 
@@ -492,8 +498,10 @@ def __init__(
         .. mongodoc:: connections
 
         .. versionchanged:: 3.11
-           Added the ``tlsDisableOCSPEndpointCheck`` keyword argument and
-           URI option.
+           Added the following keyword arguments and URI options:
+
+             - ``tlsDisableOCSPEndpointCheck``
+             - ``directConnection``
 
         .. versionchanged:: 3.9
            Added the ``retryReads`` keyword argument and URI option.
@@ -707,7 +715,8 @@ def __init__(
             server_selection_timeout=options.server_selection_timeout,
             server_selector=options.server_selector,
             heartbeat_frequency=options.heartbeat_frequency,
-            fqdn=fqdn)
+            fqdn=fqdn,
+            direct_connection=options.direct_connection)
 
         self._topology = Topology(self._topology_settings)
         if connect:

pymongo/server_description.py

@@ -216,8 +216,8 @@ def retryable_reads_supported(self):
     def topology_version(self):
         return self._topology_version
 
-    def to_unknown(self):
-        unknown = ServerDescription(self.address)
+    def to_unknown(self, error=None):
+        unknown = ServerDescription(self.address, error=error)
         unknown._topology_version = self.topology_version
         return unknown
 

pymongo/settings.py

@@ -38,7 +38,8 @@ def __init__(self,
                  server_selection_timeout=SERVER_SELECTION_TIMEOUT,
                  heartbeat_frequency=common.HEARTBEAT_FREQUENCY,
                  server_selector=None,
-                 fqdn=None):
+                 fqdn=None,
+                 direct_connection=None):
         """Represent MongoClient's configuration.
 
         Take a list of (host, port) pairs and optional replica set name.
@@ -59,7 +60,12 @@ def __init__(self,
         self._server_selector = server_selector
         self._fqdn = fqdn
         self._heartbeat_frequency = heartbeat_frequency
-        self._direct = (len(self._seeds) == 1 and not replica_set_name)
+
+        if direct_connection is None:
+            self._direct = (len(self._seeds) == 1 and not self.replica_set_name)
+        else:
+            self._direct = direct_connection
+
         self._topology_id = ObjectId()
         # Store the allocation traceback to catch unclosed clients in the
         # test suite.

pymongo/topology_description.py

@@ -337,6 +337,14 @@ def updated_topology_description(topology_description, server_description):
     sds[address] = server_description
 
     if topology_type == TOPOLOGY_TYPE.Single:
+        # Set server type to Unknown if replica set name does not match.
+        if (set_name is not None and
+                set_name != server_description.replica_set_name):
+            error = ConfigurationError(
+                "client is configured to connect to a replica set named "
+                "'%s' but this node belongs to a set named '%s'" % (
+                    set_name, server_description.replica_set_name))
+            sds[address] = server_description.to_unknown(error=error)
         # Single type never changes.
         return TopologyDescription(
             TOPOLOGY_TYPE.Single,
@@ -348,8 +356,11 @@ def updated_topology_description(topology_description, server_description):
 
     if topology_type == TOPOLOGY_TYPE.Unknown:
         if server_type == SERVER_TYPE.Standalone:
-            sds.pop(address)
-
+            if len(topology_description._topology_settings.seeds) == 1:
+                topology_type = TOPOLOGY_TYPE.Single
+            else:
+                # Remove standalone from Topology when given multiple seeds.
+                sds.pop(address)
         elif server_type not in (SERVER_TYPE.Unknown, SERVER_TYPE.RSGhost):
             topology_type = _SERVER_TYPE_TO_TOPOLOGY_TYPE[server_type]
 

pymongo/uri_parser.py

@@ -479,6 +479,10 @@ def parse_uri(uri, default_port=DEFAULT_PORT, validate=True, warn=False,
     fqdn = None
 
     if is_srv:
+        if options.get('directConnection'):
+            raise ConfigurationError(
+                "Cannot specify directConnection=true with "
+                "%s URIs" % (SRV_SCHEME,))
         nodes = split_hosts(hosts, default_port=None)
         if len(nodes) != 1:
             raise InvalidURI(
@@ -508,6 +512,9 @@ def parse_uri(uri, default_port=DEFAULT_PORT, validate=True, warn=False,
             options["ssl"] = True if validate else 'true'
     else:
         nodes = split_hosts(hosts, default_port=default_port)
+        if len(nodes) > 1 and options.get('directConnection'):
+            raise ConfigurationError(
+                "Cannot specify multiple hosts with directConnection=true")
 
     return {
         'nodelist': nodes,

test/discovery_and_monitoring/rs/discover_arbiters.json

@@ -1,6 +1,6 @@
 {
-  "description": "Discover arbiters",
-  "uri": "mongodb://a/?replicaSet=rs",
+  "description": "Discover arbiters with directConnection URI option",
+  "uri": "mongodb://a/?directConnection=false",
   "phases": [
     {
       "responses": [

test/discovery_and_monitoring/rs/discover_arbiters_replicaset.json

@@ -0,0 +1,41 @@
+{
+  "description": "Discover arbiters with replicaSet URI option",
+  "uri": "mongodb://a/?replicaSet=rs",
+  "phases": [
+    {
+      "responses": [
+        [
+          "a:27017",
+          {
+            "ok": 1,
+            "ismaster": true,
+            "hosts": [
+              "a:27017"
+            ],
+            "arbiters": [
+              "b:27017"
+            ],
+            "setName": "rs",
+            "minWireVersion": 0,
+            "maxWireVersion": 6
+          }
+        ]
+      ],
+      "outcome": {
+        "servers": {
+          "a:27017": {
+            "type": "RSPrimary",
+            "setName": "rs"
+          },
+          "b:27017": {
+            "type": "Unknown",
+            "setName": null
+          }
+        },
+        "topologyType": "ReplicaSetWithPrimary",
+        "logicalSessionTimeoutMinutes": null,
+        "setName": "rs"
+      }
+    }
+  ]
+}