Cron Offset Tasks

allianceauth/crontab/utils.py

@@ -0,0 +1,41 @@
+from celery.schedules import crontab
+import logging
+from allianceauth.crontab.models import CronOffset
+from django.db import ProgrammingError
+
+
+logger = logging.getLogger(__name__)
+
+
+def offset_cron(schedule: crontab) -> crontab:
+    """Take a crontab and apply a series of precalculated offsets to spread out tasks execution on remote resources
+
+    Args:
+        schedule (crontab): celery.schedules.crontab()
+
+    Returns:
+        crontab: A crontab with offsetted Minute and Hour fields
+    """
+
+    try:
+        cron_offset = CronOffset.get_solo()
+        new_minute = [(m + (round(60 * cron_offset.minute))) % 60 for m in schedule.minute]
+        new_hour = [(m + (round(24 * cron_offset.hour))) % 24 for m in schedule.hour]
+
+        return crontab(
+            minute=",".join(str(m) for m in sorted(new_minute)),
+            hour=",".join(str(h) for h in sorted(new_hour)),
+            day_of_month=schedule._orig_day_of_month,
+            month_of_year=schedule._orig_month_of_year,
+            day_of_week=schedule._orig_day_of_week)
+
+    except ProgrammingError as e:
+        # If this is called before migrations are run hand back the default schedule
+        # These offsets are stored in a Singleton Model,
+        logger.error(e)
+        return schedule
+
+    except Exception as e:
+        # We absolutely cant fail to hand back a schedule
+        logger.error(e)
+        return schedule