check_computer_memory: be more consistent with getFreeMemory return value

avoid to return exit code (int) or mem (object)
better return a tuple (mem, error_message) (object, str)

slapos/promise/check_computer_memory/__init__.py

@@ -23,8 +23,7 @@ def getFreeMemory(database, time, date):
     query_result = database.select("computer", date, "memory_size", limit=1) 
     result = zip(*query_result)
     if not result or not result[0][0]:
-      print "couldn't fetch total memory, collectordb is empty?"
-      return 0
+      return (None, "couldn't fetch total memory, collectordb is empty?")
     mem['total'] = result[0][0]
 
     # fetch free and used memory 
@@ -32,17 +31,15 @@ def getFreeMemory(database, time, date):
     query_result = database.select("system", date, "memory_free, memory_used", where=where_query)
     result = zip(*query_result)
     if not result or not result[0][0]: 
-      print "couldn't fetch free memory"
-      return 0
+      return (None, "couldn't fetch free memory")
     mem['free'] = result[0][0]
     if not result or not result[1][0]: 
-      print "couldn't fetch used memory"
-      return 0
+      return (None, "couldn't fetch used memory")
     mem['used'] = result[1][0]
   finally:
     database.close()
 
-  return mem
+  return (mem, "")
 
 def main():
   parser = argparse.ArgumentParser()
@@ -58,11 +55,12 @@ def main():
   db_path = args.collectordb
 
   if db_path.endswith("collector.db"):db_path=db_path[:-len("collector.db")]
-  memory = getFreeMemory(db_path, currenttime, currentdate)
+  memory, error = getFreeMemory(db_path, currenttime, currentdate)
+  if error:
+    print error
+    return 0
   threshold = float(memory['total']) * 0.2
 
-  if memory is 0:
-    return 0
   if memory['used'] <= threshold:
     print "OK - memory used: {:d}% ({}B of {}B)".format(memory["used"] * 100 / memory["total"], memory["used"], memory["total"])
     return 0

slapos/test/promise/test_check_computer_memory.py

@@ -32,6 +32,8 @@ import sqlite3
 from slapos.test.promise import data
 from slapos.promise.check_computer_memory import getFreeMemory
 
+total_memory_fetch_failure_message = "couldn't fetch total memory, collectordb is empty?"
+
 class TestComputerMemory(unittest.TestCase):
 
   def setUp(self):
@@ -47,11 +49,14 @@ class TestComputerMemory(unittest.TestCase):
     self.conn.close() 
 
   def test_check_memory(self):
-    self.assertEquals({'total': 33705312256.0, 'used': 33139023872.0, 'free': 566288384.0},
+    self.assertEquals(({'total': 33705312256.0, 'used': 33139023872.0, 'free': 566288384.0}, ""),
       getFreeMemory('/tmp', '00:02', '2017-09-15'))
 
   def test_check_memory_with_unavailable_dates(self):
-    self.assertEquals(0, getFreeMemory('/tmp', '18:00', '2017-09-14'))
+    self.assertEquals(
+      (None, total_memory_fetch_failure_message),
+      getFreeMemory('/tmp', '18:00', '2017-09-14'),
+    )
 
   def tearDown(self):
     if os.path.exists(self.db_file):