feat: minimum scheduler age before task-creation-check

charts/airflow/docs/faq/monitoring/scheduler-liveness-probe.md

@@ -12,14 +12,6 @@ for each airflow scheduler which regularly queries the Airflow Metadata Database
 A scheduler is "healthy" if it has had a "heartbeat" in the last `AIRFLOW__SCHEDULER__SCHEDULER_HEALTH_CHECK_THRESHOLD` seconds.
 Each scheduler will perform a "heartbeat" every `AIRFLOW__SCHEDULER__SCHEDULER_HEARTBEAT_SEC` seconds by updating the `latest_heartbeat` of its `SchedulerJob` in the Airflow Metadata `jobs` table.
 
-> 🟥 __Warning__ 🟥
->
-> A scheduler can have a "heartbeat" but be deadlocked such that it's unable to schedule new tasks,
-> we provide the [`scheduler.livenessProbe.taskCreationCheck.*`](#scheduler-task-creation-check) values to automatically restart the scheduler in these cases.
->
-> - https://github.com/apache/airflow/issues/7935 - patched in airflow `2.0.2`
-> - https://github.com/apache/airflow/issues/15938 - patched in airflow `2.1.1`
-
 By default, the chart runs a liveness probe every __30 seconds__ (`periodSeconds`), and will restart a scheduler if __5 probe failures__ (`failureThreshold`) occur in a row.
 This means a scheduler must be unhealthy for at least `30 x 5 = 150` seconds before Kubernetes will automatically restart a scheduler Pod.
 
@@ -49,6 +41,14 @@ scheduler:
     failureThreshold: 5
 ```
 
+> 🟥 __Warning__ 🟥
+>
+> A scheduler can have a "heartbeat" but be deadlocked such that it's unable to schedule new tasks,
+> the ["task creation check"](#scheduler-task-creation-check) should detect these situations and force a scheduler restart.
+> 
+> - https://github.com/apache/airflow/issues/7935 - patched in airflow `2.0.2`
+> - https://github.com/apache/airflow/issues/15938 - patched in airflow `2.1.1`
+
 ## Scheduler "Task Creation Check"
 
 The liveness probe can additionally check if the Scheduler is creating new [tasks](https://airflow.apache.org/docs/apache-airflow/stable/concepts/tasks.html) as an indication of its health.
@@ -73,6 +73,11 @@ scheduler:
       ## WARNING: must be AT LEAST equal to your shortest DAG schedule_interval
       ## WARNING: DummyOperator tasks will NOT be seen by this probe
       thresholdSeconds: 300
+
+      ## minimum number of seconds the scheduler must have run before the task creation check begins
+      ## WARNING: must be long enough for the scheduler to boot and create a task
+      ##
+      schedulerAgeBeforeCheck: 180
 ```
 
 > 🟦 __Tip__ 🟦

charts/airflow/examples/google-gke/custom-values.yaml

@@ -154,6 +154,7 @@ scheduler:
     taskCreationCheck:
       enabled: false
       thresholdSeconds: 300
+      schedulerAgeBeforeCheck: 180
 
 ###################################
 ## COMPONENT | Airflow Webserver

charts/airflow/examples/minikube/custom-values.yaml

@@ -118,6 +118,7 @@ scheduler:
     taskCreationCheck:
       enabled: false
       thresholdSeconds: 300
+      schedulerAgeBeforeCheck: 180
 
 ###################################
 ## COMPONENT | Airflow Webserver

charts/airflow/sample-values-CeleryExecutor.yaml

@@ -98,6 +98,7 @@ scheduler:
     taskCreationCheck:
       enabled: false
       thresholdSeconds: 300
+      schedulerAgeBeforeCheck: 180
 
 ###################################
 ## COMPONENT | Airflow Webserver

charts/airflow/sample-values-CeleryKubernetesExecutor.yaml

@@ -126,6 +126,7 @@ scheduler:
     taskCreationCheck:
       enabled: false
       thresholdSeconds: 300
+      schedulerAgeBeforeCheck: 180
 
 ###################################
 ## COMPONENT | Airflow Webserver

charts/airflow/sample-values-KubernetesExecutor.yaml

@@ -126,6 +126,7 @@ scheduler:
     taskCreationCheck:
       enabled: false
       thresholdSeconds: 300
+      schedulerAgeBeforeCheck: 180
 
 ###################################
 ## COMPONENT | Airflow Webserver

charts/airflow/templates/scheduler/scheduler-deployment.yaml

@@ -149,6 +149,9 @@ spec:
                   {{- end }}
 
                   with create_session() as session:
+                      ########################
+                      # heartbeat check
+                      ########################
                       # ensure the SchedulerJob with most recent heartbeat for this `hostname` is alive
                       hostname = get_hostname()
                       scheduler_job = session \
@@ -161,29 +164,37 @@ spec:
                           pass
                       else:
                           sys.exit(f"The SchedulerJob (id={scheduler_job.id}) for hostname '{hostname}' is not alive")
-
                       {{- if .Values.scheduler.livenessProbe.taskCreationCheck.enabled }}
+                      {{- $min_scheduler_age := .Values.scheduler.livenessProbe.taskCreationCheck.schedulerAgeBeforeCheck }}
+                      {{- if not (or (typeIs "float64" $min_scheduler_age) (typeIs "int64" $min_scheduler_age)) }}
+                      {{- /* the type of a number could be float64 or int64 depending on how it was set (values.yaml, or --set) */ -}}
+                      {{ required (printf "`scheduler.livenessProbe.taskCreationCheck.schedulerAgeBeforeCheck` must be int-type, but got %s!" (typeOf $min_scheduler_age)) nil }}
+                      {{- end }}
                       {{- $task_job_threshold := .Values.scheduler.livenessProbe.taskCreationCheck.thresholdSeconds }}
                       {{- if not (or (typeIs "float64" $task_job_threshold) (typeIs "int64" $task_job_threshold)) }}
                       {{- /* the type of a number could be float64 or int64 depending on how it was set (values.yaml, or --set) */ -}}
                       {{ required (printf "`scheduler.livenessProbe.taskCreationCheck.thresholdSeconds` must be int-type, but got %s!" (typeOf $task_job_threshold)) nil }}
                       {{- end }}
-
-                      # ensure the most recent LocalTaskJob had a start_date in the last `task_job_threshold` seconds
-                      task_job_threshold = {{ $task_job_threshold }}
-                      task_job = session \
-                          .query(LocalTaskJob) \
-                          .order_by(LocalTaskJob.id.desc()) \
-                          .limit(1) \
-                          .first()
-                      if task_job is not None:
-                          if (timezone.utcnow() - task_job.start_date).total_seconds() < task_job_threshold:
-                              pass
-                          else:
-                              sys.exit(
-                                  f"The most recent LocalTaskJob (id={task_job.id}, dag_id={task_job.dag_id}) "
-                                  f"started over {task_job_threshold} seconds ago"
-                              )
+                      ########################
+                      # task creation check
+                      ########################
+                      min_scheduler_age = {{ $min_scheduler_age }}
+                      if (timezone.utcnow() - scheduler_job.start_date).total_seconds() > min_scheduler_age:
+                          # ensure the most recent LocalTaskJob had a start_date in the last `task_job_threshold` seconds
+                          task_job_threshold = {{ $task_job_threshold }}
+                          task_job = session \
+                              .query(LocalTaskJob) \
+                              .order_by(LocalTaskJob.id.desc()) \
+                              .limit(1) \
+                              .first()
+                          if task_job is not None:
+                              if (timezone.utcnow() - task_job.start_date).total_seconds() < task_job_threshold:
+                                  pass
+                              else:
+                                  sys.exit(
+                                      f"The most recent LocalTaskJob (id={task_job.id}, dag_id={task_job.dag_id}) "
+                                      f"started over {task_job_threshold} seconds ago"
+                                  )
                       {{- end }}
           {{- end }}
           {{- if or ($volumeMounts) (include "airflow.executor.kubernetes_like" .) }}

charts/airflow/values.yaml

@@ -618,6 +618,11 @@ scheduler:
       ##
       thresholdSeconds: 300
 
+      ## minimum number of seconds the scheduler must have run before the task creation check begins
+      ## - [WARNING] must be long enough for the scheduler to boot and create a task
+      ##
+      schedulerAgeBeforeCheck: 180
+
   ## extra pip packages to install in the scheduler Pods
   ##
   ## ____ EXAMPLE _______________