Allow for configurable scheduler fallback period (#1759)

* Allow for configurable scheduler fallback period

This adds a parameter to the Scheduler called
`fallback_period`, which determines the period
before work fallsback to a new scheduler.

* Update defaults.py

Reduce Scheduler Fallback Period to 120 seconds.

* Update scheduler.py

Remove fallback period parameter.

rq/defaults.py

@@ -8,5 +8,6 @@ DEFAULT_JOB_MONITORING_INTERVAL = 30
 DEFAULT_RESULT_TTL = 500
 DEFAULT_FAILURE_TTL = 31536000  # 1 year in seconds
 DEFAULT_LOGGING_DATE_FORMAT = '%H:%M:%S'
+DEFAULT_SCHEDULER_FALLBACK_PERIOD = 120
 DEFAULT_LOGGING_FORMAT = '%(asctime)s %(message)s'
 CALLBACK_TIMEOUT = 60

rq/scheduler.py

@@ -9,7 +9,8 @@ from multiprocessing import Process
 
 from redis import SSLConnection, UnixDomainSocketConnection
 
-from .defaults import DEFAULT_LOGGING_DATE_FORMAT, DEFAULT_LOGGING_FORMAT
+from .defaults import (DEFAULT_LOGGING_DATE_FORMAT, DEFAULT_LOGGING_FORMAT,
+                       DEFAULT_SCHEDULER_FALLBACK_PERIOD)
 from .job import Job
 from .logutils import setup_loghandlers
 from .queue import Queue
@@ -98,7 +99,7 @@ class RQScheduler:
             return False
         if not self.lock_acquisition_time:
             return True
-        return (datetime.now() - self.lock_acquisition_time).total_seconds() > 600
+        return (datetime.now() - self.lock_acquisition_time).total_seconds() > DEFAULT_SCHEDULER_FALLBACK_PERIOD
 
     def acquire_locks(self, auto_start=False):
         """Returns names of queue it successfully acquires lock on"""