DOCSP-33760 Read Write Sync FAQ (#193) (#214)

* DOCSP-33760 Read Write Sync FAQ (#193)

* DOCSP-33760 Read Write Sync FAQ

* typos

* *

* JA feedback

* switch order

* *

* JA feedback

* external feedback

* final feedback

* underline too short

Author: ajhuh-mdb

source/faq.txt

@@ -17,6 +17,24 @@ This page provides answers to some frequently asked questions we have
 encountered. If you have additional questions please contact MongoDB
 Support.
 
+Can I perform reads or writes to my destination cluster while ``mongosync`` is syncing?
+---------------------------------------------------------------------------------------
+
+You can perform reads during synchronization if ``canCommit`` is ``true``. 
+However, the data that you read is 
+:term:`eventually consistent <eventual consistency>`, meaning that you might not 
+always read the latest writes.
+
+During an ongoing sync, you can write to any non-synced namespaces in the 
+destination cluster as long as the source cluster doesn’t include a namespace 
+with the same name. If you write to a synced namespace before issuing a 
+:ref:`commit <c2c-api-commit>` and while ``canWrite`` is ``false``, the behavior 
+is undefined. To avoid this undefined behavior, you can enable 
+:ref:`write blocking <c2c-dr-write-blocking>`.
+
+To check the value of ``canCommit`` or ``canWrite``, call the :ref:`progress 
+<c2c-api-progress>` API endpoint.
+
 Can ``mongosync`` run on its own hardware? 
 ------------------------------------------
 
@@ -116,7 +134,7 @@ source and destination clusters.  If the clusters are underprovisioned for your
 needs, consider upgrading the cluster hardware.
 
 Should I stop a migration if the logs contain the word "error" or "failure"?
---------------------------------------------------------------------------
+----------------------------------------------------------------------------
 
 No, logs that contain the word "error" or "failure" show non-fatal
 errors and do not signal that you need to stop ``mongosync`` early.

source/includes/fact-read-operations-check.rst

@@ -0,0 +1,2 @@
+When the :ref:`/progress <c2c-api-progress>` endpoint reports ``canWrite`` is 
+``true``, the data on the source and destination clusters is consistent.

source/includes/fact-read-operations-source.rst

@@ -0,0 +1 @@
+Read operations on the source cluster are always permitted.

source/includes/fact-write-blocking-requirement.rst

@@ -7,5 +7,3 @@ role that includes the :authaction:`setUserWriteBlockMode` and
    When using ``enableUserWriteBlocking``, writes are only blocked for users
    that do not have the :authaction:`bypassWriteBlockingMode` ActionType. Users
    who have this ActionType are able to perform writes.
-
-

source/reference/mongosync-states.txt

@@ -77,26 +77,3 @@ operations in that state.
    * - ``COMMITTED``
      - The cutover for the sync process is complete.
      - - ``GET`` :ref:`/progress <c2c-api-progress>`
-
-Read Operations
----------------
-
-Read operations on the source cluster are always permitted.
-
-When the ``/progress`` endpoint reports ``canWrite`` is ``true``, the
-data on the source and destination clusters is consistent.
-
-Write Operations
-----------------
-
-.. include:: /includes/fact-write-blocking-check.rst
-
-.. include:: /includes/fact-write-blocking-when.rst
-
-Write-blocking
-~~~~~~~~~~~~~~
-
-.. include:: /includes/fact-write-blocking-enable.rst
-
-.. include:: /includes/fact-write-blocking-requirement.rst
-

source/reference/mongosync.txt

@@ -218,6 +218,52 @@ User Permissions
 
 .. include:: /includes/fact-write-blocking-requirement.rst
 
+Permissible Reads
+`````````````````
+
+.. include:: /includes/fact-read-operations-source.rst
+
+.. include:: /includes/fact-read-operations-check.rst
+
+Permissible Writes
+``````````````````
+
+.. include:: /includes/fact-write-blocking-check.rst
+
+.. include:: /includes/fact-write-blocking-when.rst
+
+Commit
+~~~~~~
+
+To stop syncing, use the :ref:`commit <c2c-api-commit>` command on the
+destination cluster to convert indexes and finalize the changes. If you
+enable :ref:`write-blocking <c2c-write-blocking>`:
+
+
+- ``commit`` blocks writes on the source cluster. 
+- ``commit`` blocks writes on the destination cluster until
+  ``mongosync`` begins index validation.
+
+
+To monitor the ``commit`` process, use the :ref:`progress
+<c2c-api-progress>` command:
+
+- The destination cluster is writable when ``canWrite`` is true.
+- Index conversion is complete when ``mongosync`` enters the
+  ``COMMITTED`` state.
+
+User Permissions
+````````````````
+
+.. include:: /includes/fact-write-blocking-requirement.rst
+
+Permissible Reads
+`````````````````
+
+.. include:: /includes/fact-read-operations-source.rst
+
+.. include:: /includes/fact-read-operations-check.rst
+
 Permissible Writes
 ``````````````````