DOCS-13423: 4.2.2 waitingForLatches currentOp

Author: kay-kim

source/includes/currentOp-output-example.rst

@@ -62,6 +62,10 @@
                          },
                          "killPending" : <boolean>,
                          "numYields" : <number>,
+                         "waitingForLatch" : {                   // Starting in MongoDB 4.2.2
+                             "timestamp" : <ISODate()>,
+                             "captureName" : <string>
+                         },
                          "locks" : {
                              "ParallelBatchWriterMode" : <string>,
                              "ReplicationStateTransition" : <string>,
@@ -195,6 +199,10 @@
                         },
                         "killPending" : <boolean>,
                         "numYields" : <number>,
+                         "waitingForLatch" : {                   // Starting in MongoDB 4.2.2
+                             "timestamp" : <ISODate()>,
+                             "captureName" : <string>
+                         },
                         "locks" : {
                             "ParallelBatchWriterMode" : <string>,
                             "ReplicationStateTransition" : <string>,
@@ -353,6 +361,10 @@
                          },
                          "killPending" : <boolean>,
                          "numYields" : <number>,
+                         "waitingForLatch" : {                   // Starting in MongoDB 4.2.2
+                             "timestamp" : <ISODate()>,
+                             "captureName" : <string>
+                         },
                          "locks" : {
                              "ParallelBatchWriterMode" : <string>,
                              "ReplicationStateTransition" : <string>,

source/reference/command/currentOp.txt

@@ -896,6 +896,38 @@ Output Fields
 
    .. include:: /includes/fact-client-appname.rst
 
+.. data:: currentOp.waitingForLatch
+
+   The :data:`~currentOp.waitingForLatch` document is only
+   available if the operation is waiting to acquire an internal locking
+   primitive (a.k.a. a latch) or for an internal condition to be met.
+
+   For example,
+   
+   .. code-block:: javascript
+
+      "waitingForLatch" : {
+         "timestamp" : ISODate("2020-03-19T23:25:58.412Z"),
+         "captureName" : "FutureResolution",
+      },
+
+   .. list-table::
+      :header-rows: 1
+      :widths: 20 80
+
+      * - Output Field
+        - Description
+
+      * - timestamp
+
+        - The date and time at which the operation started to wait.
+
+      * - captureName
+
+        - The internal name of the section where the operation is currently blocked.
+
+   .. versionadded:: 4.2.2
+
 .. data:: currentOp.locks
 
    The :data:`~currentOp.locks` document reports the type and mode of

source/reference/operator/aggregation/currentOp.txt

@@ -165,6 +165,26 @@ Syntax
 
        .. versionadded:: 4.0
 
+   * - :ref:`backtrace <currentOp-stage-backtrace>`
+
+     - .. _currentOp-stage-backtrace:
+
+       Boolean. Determines whether callstack information is returned as
+       part of the :data:`~$currentOp.waitingForLatch` output field.
+
+       - If set to ``true``, :pipeline:`$currentOp` includes
+         :data:`waitingForLatch.backtrace <$currentOp.waitingForLatch>`
+         field that contains the callstack information, if available.
+         If unavailable, the field contains an empty array.
+
+       - If set to ``false``, :pipeline:`$currentOp` omits the
+         :data:`waitingForLatch.backtrace <$currentOp.waitingForLatch>`
+         field.
+
+       Defaults to ``false``.
+
+       .. versionadded:: 4.2.2
+
 Omitting any of the above parameters will cause $currentOp to use
 that parameter's default value. Specify an empty document, as shown
 below, to use the default values of all parameters.
@@ -1361,6 +1381,45 @@ relevant for the operation:
    other operations that have data in memory to complete quickly
    while MongoDB reads in data for the yielding operation.
 
+
+.. data:: $currentOp.waitingForLatch
+
+   The :data:`~$currentOp.waitingForLatch` document is only
+   available if the operation is waiting to acquire an internal locking
+   primitive (a.k.a. a latch) or for an internal condition to be met.
+
+   For example,
+   
+   .. code-block:: javascript
+
+      "waitingForLatch" : {
+         "timestamp" : ISODate("2020-03-19T23:25:58.412Z"),
+         "captureName" : "FutureResolution",
+         "backtrace" : [ ]   // Only if backtrace: true
+      },
+
+   .. list-table::
+      :header-rows: 1
+      :widths: 20 80
+
+      * - Output Field
+        - Description
+
+      * - timestamp
+
+        - The date and time at which the operation started to wait.
+
+      * - captureName
+
+        - The internal name of the section where the operation is currently blocked.
+
+      * - backtrace
+
+        - The callstack, if available. The field is only included if
+          :ref:`backtrace: true <currentOp-stage-backtrace>`.
+
+   .. versionadded:: 4.2.2
+
 .. data:: $currentOp.locks
 
    The :data:`~$currentOp.locks` document reports the type and mode of