Use the new simple lock decorator to simplify a job processor task

apps/job_processor/tasks.py

@@ -1,55 +1,47 @@
 from __future__ import absolute_import
 
-from datetime import timedelta, datetime
-import platform
 import logging
-import psutil
 
 from lock_manager import Lock, LockError
+from lock_manager.decorators import simple_locking
 
 from .models import Node, JobQueue
 from .exceptions import JobQueueNoPendingJobs
 
 LOCK_EXPIRE = 10
 # TODO: Tie LOCK_EXPIRATION with hard task timeout
+MAX_CPU_LOAD = 90
+MAX_MEMORY_USAGE = 90
 
 logger = logging.getLogger(__name__)
 
 
+@simple_locking('refresh_node', 10)
 def refresh_node():
     logger.debug('starting')
-
-    lock_id = u'refresh_node'
-    try:
-        logger.debug('trying to acquire lock: %s' % lock_id)
-        lock = Lock.acquire_lock(lock_id, LOCK_EXPIRE)
-        logger.debug('acquired lock: %s' % lock_id)
-        node = Node.objects.myself()  # Automatically calls the refresh() method too
-        lock.release()
-    except LockError:
-        logger.debug('unable to obtain lock')
-    except Exception:
-        lock.release()
-        raise
+    node = Node.objects.myself()  # Automatically calls the refresh() method too
 
 
 def job_queue_poll():
     logger.debug('starting')
 
-    lock_id = u'job_queue_poll'
-    try:
-        logger.debug('trying to acquire lock: %s' % lock_id)
-        lock = Lock.acquire_lock(lock_id, LOCK_EXPIRE)
-        logger.debug('acquired lock: %s' % lock_id)
-        for job_queue in JobQueue.objects.all():
-            try:
-                job_item = job_queue.get_oldest_pending_job()
-                job_item.run()
-            except JobQueueNoPendingJobs:
-                logger.debug('no pending jobs for job queue: %s' % job_queue)
-        lock.release()
-    except LockError:
-        logger.debug('unable to obtain lock')
-    except Exception:
-        lock.release()
-        raise
+    node = Node.objects.myself()  # Automatically calls the refresh() method too
+    if node.cpuload < MAX_CPU_LOAD and node.memory_usage < MAX_MEMORY_USAGE:
+        # Poll job queues is node is not overloaded
+        lock_id = u'job_queue_poll'
+        try:
+            lock = Lock.acquire_lock(lock_id, LOCK_EXPIRE)
+        except LockError:
+            pass
+        except Exception:
+            lock.release()
+            raise
+        else:
+            for job_queue in JobQueue.objects.all():
+                try:
+                    job_item = job_queue.get_oldest_pending_job()
+                    job_item.run()
+                except JobQueueNoPendingJobs:
+                    logger.debug('no pending jobs for job queue: %s' % job_queue)
+            lock.release()
+