Checks if cpu_count is implemented

On rare occasions, usually on win32, cpu_count will raise a NotImplemented error.  If psutil is installed we will use this to get the correct count, otherwise we default to 4

django_q/cluster.py

@@ -22,12 +22,6 @@ from multiprocessing import Queue, Event, Process, Value, current_process
 # external
 import arrow
 
-# optional
-try:
-    import psutil
-except ImportError:
-    psutil = None
-
 # Django
 from django.utils import timezone
 from django.utils.translation import ugettext_lazy as _
@@ -37,7 +31,7 @@ from django import db
 import signing
 import tasks
 
-from django_q.conf import Conf, redis_client, logger
+from django_q.conf import Conf, redis_client, logger, psutil
 from django_q.models import Task, Success, Schedule
 from django_q.monitor import Status, Stat
 

django_q/conf.py

@@ -2,10 +2,19 @@ import logging
 from signal import signal
 from multiprocessing import cpu_count, Queue
 
+# django
 from django.utils.translation import ugettext_lazy as _
 from django.conf import settings
+
+# external
 import redis
 
+# optional
+try:
+    import psutil
+except ImportError:
+    psutil = None
+
 
 class Conf(object):
     """
@@ -36,8 +45,19 @@ class Conf(object):
     # Maximum number of tasks that each cluster can work on
     QUEUE_LIMIT = conf.get('queue_limit', None)
 
-    # Number of workers in the pool. Default is cpu count. +2 for monitor and pusher
-    WORKERS = conf.get('workers', cpu_count())
+    # Number of workers in the pool. Default is cpu count if implemented, otherwise 4.
+    WORKERS = conf.get('workers', False)
+    if not WORKERS:
+        try:
+            WORKERS = cpu_count()
+            # in rare cases this might fail
+        except NotImplementedError:
+            # try psutil
+            if psutil:
+                WORKERS = psutil.cpu_count() or 4
+            else:
+                # sensible default
+                WORKERS = 4
 
     # Sets compression of redis packages
     COMPRESSED = conf.get('compress', False)