[GitHub] [airflow] XD-DENG commented on a change in pull request #12835: Don't emit first_task_scheduling_delay metric for only-once dags

[GitBox <gi...@apache.org>]

XD-DENG commented on a change in pull request #12835:
URL: https://github.com/apache/airflow/pull/12835#discussion_r536811076



##########
File path: airflow/models/dagrun.py
##########
@@ -573,23 +573,29 @@ def _emit_true_scheduling_delay_stats_for_finished_state(self, finished_tis):
         Note, the stat will only be emitted if the DagRun is a scheduler triggered one
         (i.e. external_trigger is False).
         """
+        if self.state == State.RUNNING:
+            return
+        if self.external_trigger:
+            return
+        if not finished_tis:
+            return
+
         try:
-            if self.state == State.RUNNING:
-                return
-            if self.external_trigger:
-                return
-            if not finished_tis:
-                return
             dag = self.get_dag()
+
+            if not self.dag.schedule_interval or self.dag.schedule_interval == "@once":
+                # We can't emit this metric if there is no following schedule to cacluate from!
+                return
+
             ordered_tis_by_start_date = [ti for ti in finished_tis if ti.start_date]
             ordered_tis_by_start_date.sort(key=lambda ti: ti.start_date, reverse=False)
             first_start_date = ordered_tis_by_start_date[0].start_date

Review comment:
       A question not relating to the changes made in this PR: why not we directly have something like
   
   `first_start_date = min(ti.start_date for ti in finished_tis)`




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