add docs for bc_sessions_poll_delay (#1023)

source/reference/files/ondemand-d-ymls.rst

@@ -964,8 +964,28 @@ Configuration Properties
       novnc_default_quality: 2
 
   Example
-    Increas the default quality setting to 9.
+    Increase the default quality setting to 9.
 
     .. code-block:: yaml
 
       novnc_default_quality: 9
+
+.. _bc_sessions_poll_delay:
+.. describe:: bc_sessions_poll_delay (Integer, 10000)
+
+  How long the client browser should wait, in milliseconds,
+  to update the batch connect sessions page.
+
+  Default
+    The default poll delay of 10000 (10 seconds).
+
+    .. code-block:: yaml
+
+      bc_sessions_poll_delay: 10000
+
+  Example
+    Increase the poll delay to 30000 (30 seconds).
+
+    .. code-block:: yaml
+
+      bc_sessions_poll_delay: 30000

source/release-notes/v4.0-release-notes.rst

@@ -79,6 +79,16 @@ id of the form item will be lowercase as shown below.
 
   id="batch_connect_session_context_my_cool_form_item"
 
+Deprecations
+............
+
+POLL_DELAY is deprecated
+************************
+
+``POLL_DELAY`` is deprecated in 4.0 and being replaced
+by documented configurations. See `Batch connect sessions poll delay`_
+for more details.
+
 Dependency updates
 ..................
 
@@ -112,3 +122,17 @@ Sites can now set the default compression and quality values
 for noVNC batch connect applications through the two ``ondemand.d``
 properties :ref:`novnc_default_compression <novnc_default_compression>`
 and :ref:`novnc_default_quality <novnc_default_quality>`.
+
+Batch connect sessions poll delay
+.................................
+
+When a user lands on ``My Interactive Sessions`` page,
+the client browswer will request updates by default
+every 10 seconds.
+
+Sites wanting to change this had do use the hidden environment
+variable ``POLL_DELAY``.
+
+In 4.0 this is a documented configuration with ``POLL_DELAY`` being
+deprecated. See :ref:`the bc_sessions_poll_delay documentation <bc_sessions_poll_delay>`
+for more details.