[GitHub] [airflow] milton0825 commented on a change in pull request #5127: [AIRFLOW-4343] Show warning in UI if scheduler is not running

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

milton0825 commented on a change in pull request #5127: [AIRFLOW-4343] Show warning in UI if scheduler is not running
URL: https://github.com/apache/airflow/pull/5127#discussion_r277123855
 
 

 ##########
 File path: airflow/jobs.py
 ##########
 @@ -98,25 +98,48 @@ class BaseJob(Base, LoggingMixin):
         Index('idx_job_state_heartbeat', state, latest_heartbeat),
     )
 
+    heartrate = conf.getfloat('scheduler', 'JOB_HEARTBEAT_SEC'),
+
     def __init__(
             self,
             executor=executors.get_default_executor(),
-            heartrate=conf.getfloat('scheduler', 'JOB_HEARTBEAT_SEC'),
+            heartrate=None,
             *args, **kwargs):
         self.hostname = get_hostname()
         self.executor = executor
         self.executor_class = executor.__class__.__name__
         self.start_date = timezone.utcnow()
         self.latest_heartbeat = timezone.utcnow()
-        self.heartrate = heartrate
+        if heartrate is not None:
+            self.heartrate = heartrate
         self.unixname = getpass.getuser()
         self.max_tis_per_query = conf.getint('scheduler', 'max_tis_per_query')
         super(BaseJob, self).__init__(*args, **kwargs)
 
-    def is_alive(self):
+    @classmethod
+    @provide_session
+    def most_recent_job(cls, session):  # type: (Session) -> Optional[BaseJob]
+        """
+        Return the most recent job of this type, if any, based on last
+        heartbeat received.
+
+        This method should be called on a subclass (i.e. on SchedulerJob) to
+        return jobs of that type.
+
+        :rtype: BaseJob or None
+        """
+        return session.query(cls).order_by(cls.latest_heartbeat.desc()).limit(1).first()
+
+    def is_alive(self, grace_multiplier=2.1):
+        """
+        Is this job currently alive.
+
+        We define alive as in a state of RUNNING, and within a multiple of the
+        heartrate (default of 2.1)
 
 Review comment:
   +1 on an explanation on why `2.1` is chosen as default

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