Add Missing Statsd Metrics in Docs (apache#13708)

closes apache#10091

docs/apache-airflow/logging-monitoring/metrics.rst

@@ -77,32 +77,40 @@ See :doc:`../modules_management` for details on how Python and Airflow manage mo
 Counters
 --------
 
-======================================= ================================================================
-Name                                    Description
-======================================= ================================================================
-``<job_name>_start``                    Number of started ``<job_name>`` job, ex. ``SchedulerJob``, ``LocalTaskJob``
-``<job_name>_end``                      Number of ended ``<job_name>`` job, ex. ``SchedulerJob``, ``LocalTaskJob``
-``operator_failures_<operator_name>``   Operator ``<operator_name>`` failures
-``operator_successes_<operator_name>``  Operator ``<operator_name>`` successes
-``ti_failures``                         Overall task instances failures
-``ti_successes``                        Overall task instances successes
-``zombies_killed``                      Zombie tasks killed
-``scheduler_heartbeat``                 Scheduler heartbeats
-``dag_processing.processes``            Number of currently running DAG parsing processes
-``scheduler.tasks.killed_externally``   Number of tasks killed externally
-``scheduler.tasks.running``             Number of tasks running in executor
-``scheduler.tasks.starving``            Number of tasks that cannot be scheduled because of no open slot in pool
-``scheduler.orphaned_tasks.cleared``    Number of Orphaned tasks cleared by the Scheduler
-``scheduler.orphaned_tasks.adopted``    Number of Orphaned tasks adopted by the Scheduler
-``scheduler.critical_section_busy``     Count of times a scheduler process tried to get a lock on the critical
-                                        section (needed to send tasks to the executor) and found it locked by
-                                        another process.
-``sla_email_notification_failure``      Number of failed SLA miss email notification attempts
-``ti.start.<dagid>.<taskid>``           Number of started task in a given dag. Similar to <job_name>_start but for task
-``ti.finish.<dagid>.<taskid>.<state>``  Number of completed task in a given dag. Similar to <job_name>_end but for task
-``dag.callback_exceptions``             Number of exceptions raised from DAG callbacks. When this happens, it means DAG callback is not working.
-``celery.task_timeout_error``           Number of ``AirflowTaskTimeout`` errors raised when publishing Task to Celery Broker.
-======================================= ================================================================
+=========================================== ================================================================
+Name                                        Description
+=========================================== ================================================================
+``<job_name>_start``                        Number of started ``<job_name>`` job, ex. ``SchedulerJob``, ``LocalTaskJob``
+``<job_name>_end``                          Number of ended ``<job_name>`` job, ex. ``SchedulerJob``, ``LocalTaskJob``
+``<job_name>_heartbeat_failure``            Number of failed Heartbeats for a ``<job_name>`` job, ex. ``SchedulerJob``,
+                                            ``LocalTaskJob``
+``operator_failures_<operator_name>``       Operator ``<operator_name>`` failures
+``operator_successes_<operator_name>``      Operator ``<operator_name>`` successes
+``ti_failures``                             Overall task instances failures
+``ti_successes``                            Overall task instances successes
+``previously_succeeded``                    Number of previously succeeded task instances
+``zombies_killed``                          Zombie tasks killed
+``scheduler_heartbeat``                     Scheduler heartbeats
+``dag_processing.processes``                Number of currently running DAG parsing processes
+``dag_processing.manager_stalls``           Number of stalled ``DagFileProcessorManager``
+``dag_file_refresh_error``                  Number of failures loading any DAG files
+``scheduler.tasks.killed_externally``       Number of tasks killed externally
+``scheduler.orphaned_tasks.cleared``        Number of Orphaned tasks cleared by the Scheduler
+``scheduler.orphaned_tasks.adopted``        Number of Orphaned tasks adopted by the Scheduler
+``scheduler.critical_section_busy``         Count of times a scheduler process tried to get a lock on the critical
+                                            section (needed to send tasks to the executor) and found it locked by
+                                            another process.
+``sla_email_notification_failure``          Number of failed SLA miss email notification attempts
+``ti.start.<dagid>.<taskid>``               Number of started task in a given dag. Similar to <job_name>_start but for task
+``ti.finish.<dagid>.<taskid>.<state>``      Number of completed task in a given dag. Similar to <job_name>_end but for task
+``dag.callback_exceptions``                 Number of exceptions raised from DAG callbacks. When this happens, it
+                                            means DAG callback is not working.
+``celery.task_timeout_error``               Number of ``AirflowTaskTimeout`` errors raised when publishing Task to Celery Broker.
+``task_removed_from_dag.<dagid>``           Number of tasks removed for a given dag (i.e. task no longer exists in DAG)
+``task_restored_to_dag.<dagid>``            Number of tasks restored for a given dag (i.e. task instance which was
+                                            previously in REMOVED state in the DB is added to DAG file)
+``task_instance_created-<operator_name>``   Number of tasks instances created for a given Operator
+=========================================== ================================================================
 
 Gauges
 ------
@@ -116,6 +124,12 @@ Name                                                Description
 ``dag_processing.last_runtime.<dag_file>``          Seconds spent processing ``<dag_file>`` (in most recent iteration)
 ``dag_processing.last_run.seconds_ago.<dag_file>``  Seconds since ``<dag_file>`` was last processed
 ``dag_processing.processor_timeouts``               Number of file processors that have been killed due to taking too long
+``scheduler.tasks.without_dagrun``                  Number of tasks without DagRuns or with DagRuns not in Running state
+``scheduler.tasks.running``                         Number of tasks running in executor
+``scheduler.tasks.starving``                        Number of tasks that cannot be scheduled because of no open slot in pool
+``scheduler.tasks.executable``                      Number of tasks that are ready for execution (set to queued)
+                                                    with respect to pool limits, dag concurrency, executor state,
+                                                    and priority.
 ``executor.open_slots``                             Number of open slots on executor
 ``executor.queued_tasks``                           Number of queued tasks on executor
 ``executor.running_tasks``                          Number of running tasks on executor
@@ -146,4 +160,5 @@ Name                                                Description
 ``scheduler.critical_section_duration``             Milliseconds spent in the critical section of scheduler loop --
                                                     only a single scheduler can enter this loop at a time
 ``dagrun.<dag_id>.first_task_scheduling_delay``     Milliseconds elapsed between first task start_date and dagrun expected start
+``collect_db_dags``                                 Milliseconds taken for fetching all Serialized Dags from DB
 =================================================== ========================================================================