Docs 10980

source/includes/options-mongo.yaml

@@ -73,6 +73,23 @@ description: |
   the CN or SAN of the {{instance}}'s ``--sslPEMKeyFile`` certificate.
   If the hostname does not match the CN/SAN, {{program}} will fail to
   connect.
+
+  For `DNS seedlist connections <https://docs.mongodb.com/manual/reference/connection-string/#dns-seedlist-connection-format/>`_, specify the connection protocol as
+  ``mongodb+srv``, followed by the DNS SRV hostname record and any
+  options. The  ``authSource`` and ``replicaSet`` options, if included in
+  the connection string, will override any corresponding DNS-configured options 
+  set in the TXT record. Use of the ``mongodb+srv:`` connection string implicitly
+  enables SSL (normally set with ``ssl=true``) for the client connection. The
+  SSL option can be turned off by setting ``ssl=false`` in the query string.
+
+  Example:
+
+  .. code-block:: none
+
+     mongodb+srv://server.example.com/?connectionTimeout=3000ms
+
+  .. versionadded:: 3.6
+
 optional: true
 replacement:
   instance: ":program:`mongod` or :program:`mongos`"

source/reference/connection-string.txt

@@ -131,6 +131,92 @@ The components of this string are:
 
       mongodb://r1.example.net:27017,r2.example.net:27017/
 
+.. index:: connections; dns-seedlist
+.. _connections-dns-seedlist:
+
+
+DNS Seedlist Connection Format
+------------------------------
+
+.. versionadded:: 3.6
+
+In addition to the standard connection format, MongoDB supports a DNS-constructed
+seedlist. Using DNS to construct the available servers list allows more flexibility
+of deployment and the ability to change the servers in rotation without reconfiguring
+clients.
+
+In order to leverage the DNS seedlist, use a connection string prefix of ``mongodb+srv:`` 
+in place of the ``mongodb:`` string above.
+
+The ``+srv`` indicates to the mongo client that the hostname that follows corresponds to a 
+DNS SRV record. The client driver will then query the DNS for the record to determine the hosts that
+are running the mongod instances.
+
+For example, to connect to a DNS-listed hostname:
+
+    .. code-block:: none
+
+       mongodb+srv://server.example.com/
+
+A typical DNS configuration for the connection string above might look something
+like this:
+
+    .. code-block:: none
+
+       Record                            TTL   Class    Priority Weight Port  Target
+       _mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27317 mongodb1.example.com.
+       _mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27017 mongodb2.example.com.
+
+.. note::
+  The hostnames returned in SRV records must share the same parent domain (in this example,``example.com``)
+  as the given hostname.
+
+The DNS seedlist connection string can also provide options as a query string, with a trailing "/?" as in
+the standard connection string above. However, the ``+srv`` appended to the standard connection string 
+signals the driver to query the DNS for options as a configured TXT record. 
+
+Only two options are available for configuration via a TXT record -- 
+``replicaSet`` and ``authSource``, and only one TXT record
+is allowed per server. If multiple TXT records appear in the DNS and/or if the TXT record contains
+an option other than ``replicaSet`` or ``authSource``, an error will be thrown by the
+driver.
+
+An example of a properly configured TXT record:
+
+    .. code-block:: none
+
+       Record              TTL   Class    Text
+       server.example.com. 86400 IN TXT   "replicaSet=mySet&authSource=authDB"
+
+In this case, taking into account both
+the DNS SRV records and the options retrieved from the TXT records, the parsed string will look like:
+
+    .. code-block:: none
+
+       mongodb://mongodb1.example.com:27317,mongodb2.example.com:27107/?replicaSet=mySet&authSource=authDB
+
+Options set in a TXT record can be overridden by passing in a query string with the URI. In the example below,
+the query string has provided an override for the ``authSource`` option configured in the TXT record of the DNS
+entry above.
+
+    .. code-block:: none
+
+       mongodb+srv://server.example.com/?connectTimeoutMS=300000&authSource=aDifferentAuthDB
+
+The rest of the option string will remain, and we can expect that the resulting URI 
+would look like this (after parse).
+
+    .. code-block:: none
+
+       mongodb://mongodb1.example.com:27317,mongodb2.example.com:27107/?connectTimeoutMS=300000&replicaSet=mySet&authSource=aDifferentAuthDB
+
+.. note::
+   The ``mongodb+srv`` option will fail if there is no available DNS with records that correspond to the
+   hostname identified in the connection string. In addition, use of the ``+srv`` connection string modifier
+   sets the ``ssl`` option to ``true`` automatically for the connection. This can be overridden by explicitly setting
+   the ``ssl`` option to ``false`` with ``ssl=false`` in the query string.
+
+
 .. index:: connections; options
 .. _connections-connection-options: