DOCSP-34133 adding read preference info to connection strings (#213) (#219)

* empty commit

* DOCSP-34133 adding read preference info to atlas page

* DOCSP-34133 adding read preference info

* DOCSP-34133 adding read preference info

* DOCSP-34133 adding read preference info

* DOCSP-34133 adding read preference info

* DOCSP-34133 adding read preference info

* DOCSP-34133 copy edits

Author: ltran-mdb2

source/includes/fact-connection-strings-atlas.rst

@@ -28,3 +28,4 @@ hostnames of the :binary:`mongos` instances instead of the
 
    ``mongosync`` does not require the :urioption:`replicaSet` option.
 
+.. include:: /includes/read-preference-connection-string.rst

source/includes/fact-connection-strings.rst

@@ -24,3 +24,5 @@ hostnames of the :binary:`mongos` instances instead of the
 
    ``mongosync`` does not require the :urioption:`replicaSet` option.
 
+.. include:: /includes/read-preference-connection-string.rst
+

source/includes/read-preference-connection-string.rst

@@ -0,0 +1,5 @@
+You can also specify read preference on a per-connection basis in the
+connection string. By default, ``mongosync`` sets the source cluster
+read preference to :readmode:`nearest` to distribute reads evenly across
+nodes. For more information on setting read preference in connection
+strings, see :ref:`connections-read-preference`.

source/reference/mongosync.txt

@@ -301,6 +301,15 @@ the destination cluster, ``mongosync`` sets the write concern level to
 For more information on read and write concern configuration and
 behavior, see :ref:`read-concern` and :ref:`write-concern`. 
 
+Read Preference
+~~~~~~~~~~~~~~~
+
+By default, ``mongosync`` sets the source cluster read preference to
+:readmode:`nearest` to distribute reads evenly across nodes. To change
+the read preference of the source cluster, specify the read preference
+mode in the URI of the connection string. For details, see
+:ref:`connections-read-preference`. 
+
 .. _c2c-capped-collections:
 
 Capped Collections