DOCS-15960 Add duration of how long an oplog slot is kept open (#4153) (#6845)

* DOCSP-15960 Add duration of how long an oplog slot is kept open

* DOCS-15960 updates for CR feedback

* DOCSP-15960 include filename correction

* Update source/tutorial/troubleshoot-replica-sets.txt



* DOCS-15960 moved example to includes file

---------

Co-authored-by: Ashley Brown <[email protected]>

Author: kanchana-mongodb

source/includes/fact-totalOplogSlotDurationMicros.rst

@@ -0,0 +1,5 @@
+Starting in MongoDB 7.0, the ``totalOplogSlotDurationMicros`` in the
+slow query log message shows the time between a write operation getting
+a commit timestamp to commit the storage engine writes and actually
+committing. ``mongod`` supports parallel writes. However, it commits
+write operations with commit timestamps in any order. 

source/includes/fact-totalOplogSlotDurationMicrosExample.rst

@@ -0,0 +1,10 @@
+Consider the following writes with commit timestamps:
+
+- writeA with Timestamp1
+- writeB with Timestamp2
+- writeC with Timestamp3
+
+Suppose writeB commits first at Timestamp2. Replication is paused
+until writeA commits because writeA's oplog entry with Timestamp1 is
+required for replication to copy the oplog to secondary replica set
+members. 

source/reference/log-messages.txt

@@ -1023,9 +1023,14 @@ a slow :doc:`aggregation </aggregation>` operation:
 
    {"t":{"$date":"2020-05-20T20:10:08.731+00:00"},"s":"I",  "c":"COMMAND",  "id":51803,   "ctx":"conn281","msg":"Slow query","attr":{"type":"command","ns":"stocks.trades","appName":"MongoDB Shell","command":{"aggregate":"trades","pipeline":[{"$project":{"ticker":1.0,"price":1.0,"priceGTE110":{"$gte":["$price",110.0]},"_id":0.0}},{"$sort":{"price":-1.0}}],"allowDiskUse":true,"cursor":{},"lsid":{"id":{"$uuid":"fa658f9e-9cd6-42d4-b1c8-c9160fabf2a2"}},"$clusterTime":{"clusterTime":{"$timestamp":{"t":1590005405,"i":1}},"signature":{"hash":{"$binary":{"base64":"AAAAAAAAAAAAAAAAAAAAAAAAAAA=","subType":"0"}},"keyId":0}},"$db":"test"},"planSummary":"COLLSCAN","cursorid":1912190691485054730,"keysExamined":0,"docsExamined":1000001,"hasSortStage":true,"usedDisk":true,"numYields":1002,"nreturned":101,"reslen":17738,"locks":{"ReplicationStateTransition":{"acquireCount":{"w":1119}},"Global":{"acquireCount":{"r":1119}},"Database":{"acquireCount":{"r":1119}},"Collection":{"acquireCount":{"r":1119}},"Mutex":{"acquireCount":{"r":117}}},"storage":{"data":{"bytesRead":232899899,"timeReadingMicros":186017},"timeWaitingMicros":{"cache":849}},"remote": "192.168.14.15:37666","protocol":"op_msg","durationMillis":22427}}
 
-See the :ref:`examples section <log-message-json-examples>` for a
-:ref:`pretty-printed <log-message-pretty-printing>` version of this log
-entry.
+.. include:: /includes/fact-totalOplogSlotDurationMicros.rst 
+
+.. example:: 
+
+   .. include:: /includes/fact-totalOplogSlotDurationMicrosExample.rst
+
+For a :ref:`pretty-printed <log-message-pretty-printing>` example of a
+slow operation log entry, see :ref:`log-message-json-examples`.
 
 .. _log-messages-remoteOpWaitMillis:
 

source/tutorial/troubleshoot-replica-sets.txt

@@ -70,6 +70,12 @@ To check the current length of replication lag:
      The :method:`rs.status()` method is a wrapper around the
      :dbcommand:`replSetGetStatus` database command.
 
+  .. include:: /includes/fact-totalOplogSlotDurationMicros.rst
+
+  .. example::
+  
+     .. include:: /includes/fact-totalOplogSlotDurationMicrosExample.rst
+
 - Monitor the rate of replication by checking for non-zero or increasing
   oplog time values in the :guilabel:`Replication Lag` graph available in 
   `Cloud Manager <https://docs.cloudmanager.mongodb.com/reference/alerts/replication-lag/>`_