compat: darwin: fall back to default poll interval in lieu of sched_r…

…r_get_interval

resolves #13

src/fate/conf/types/task.py

@@ -9,7 +9,7 @@
 import jinja2
 from descriptors import classproperty
 
-from fate.util.compat.cpu import cpu_count
+from fate.util.compat.os import cpu_count
 from fate.util.format import Dumper, SLoader
 from fate.util.iteration import storeresult
 from fate.util.sentinel import Undefined

src/fate/sched/tiered_tenancy.py

@@ -1,9 +1,10 @@
 import collections
 import itertools
 import operator
-import os
 import time
 
+from fate.util.compat.os import get_interval
+
 from .base import TaskProcessPool, TaskScheduler
 
 
@@ -43,7 +44,7 @@ class TieredTenancyScheduler(TaskScheduler):
     """
     # Note: optimum time to wait before polling unclear.
     # For now, let's just wait a "slice":
-    poll_frequency = os.sched_rr_get_interval(0)
+    poll_frequency = get_interval()
 
     def exec_tasks(self, reset=False):
         count_completed = 0

src/fate/util/compat/cpu.py → src/fate/util/compat/os.py

@@ -2,6 +2,9 @@
 import os
 
 
+COMPAT_INTERVAL = 0.02
+
+
 def cpu_count():
     try:
         # glibc-only
@@ -11,3 +14,13 @@ def cpu_count():
         return multiprocessing.cpu_count()
     else:
         return len(sched_getaffinity(0))
+
+
+def get_interval(default=COMPAT_INTERVAL):
+    try:
+        sched_rr_get_interval = os.sched_rr_get_interval
+    except AttributeError:
+        # unsupported (e.g. darwin)
+        return default
+    else:
+        return sched_rr_get_interval(0)