Speed up tests for IssueCommand timeout handling.

test-requirements.txt

@@ -16,3 +16,4 @@ nose>=1.3
 nose-progressive>=1.5
 flake8>=2.1.0
 futures>=2.1.0
+psutil

tests/vm_util_test.py

@@ -14,7 +14,11 @@
 
 """Tests for perfkitbenchmarker.vm_util."""
 
+import os
+import psutil
 import subprocess
+import threading
+import time
 import unittest
 
 import mock
@@ -68,25 +72,76 @@ def testReachable_Unreachable(self):
         False, vm_util.IpAddressSubset.REACHABLE, False)
 
 
+def HaveSleepSubprocess():
+  """Checks if the current process has a sleep subprocess."""
+
+  for child in psutil.Process(os.getpid()).get_children(recursive=True):
+    if 'sleep' in child.cmdline:
+      return True
+  return False
+
+
+class WaitUntilSleepTimer(threading.Thread):
+  """Timer that waits for a sleep subprocess to appear.
+
+  This is intended for specific tests that want to trigger timer
+  expiry as soon as it detects that a subprocess is executing a
+  "sleep" command.
+
+  It assumes that the test driver is not parallelizing the tests using
+  this method since that may lead to inconsistent results.
+  TODO(klausw): If that's an issue, could add a unique fractional part
+  to the sleep command args to distinguish them.
+  """
+  def __init__(self, interval, function):
+    threading.Thread.__init__(self)
+    self.end_time = time.time() + interval
+    self.function = function
+    self.finished = threading.Event()
+    self.have_sleep = threading.Event()
+
+    def WaitForSleep():
+      while not self.finished.is_set():
+        if HaveSleepSubprocess():
+          self.have_sleep.set()
+          break
+        time.sleep(0)  # yield to other Python threads
+
+    threading.Thread(target=WaitForSleep).run()
+
+  def cancel(self):
+    self.finished.set()
+
+  def run(self):
+    while time.time() < self.end_time and not self.have_sleep.is_set():
+      time.sleep(0)  # yield to other Python threads
+    if not self.finished.is_set():
+      self.function()
+    self.finished.set()
+
+
 class IssueCommandTestCase(unittest.TestCase):
 
   def testTimeoutNotReached(self):
-    _, _, retcode = vm_util.IssueCommand(['sleep', '2s'])
+    _, _, retcode = vm_util.IssueCommand(['sleep', '0s'])
     self.assertEqual(retcode, 0)
 
+  @mock.patch('threading.Timer', new=WaitUntilSleepTimer)
   def testTimeoutReached(self):
     _, _, retcode = vm_util.IssueCommand(['sleep', '2s'], timeout=1)
     self.assertEqual(retcode, -9)
+    self.assertFalse(HaveSleepSubprocess())
 
   def testNoTimeout(self):
-    _, _, retcode = vm_util.IssueCommand(['sleep', '2s'], timeout=None)
+    _, _, retcode = vm_util.IssueCommand(['sleep', '0s'], timeout=None)
     self.assertEqual(retcode, 0)
 
   def testNoTimeout_ExceptionRaised(self):
     with mock.patch('subprocess.Popen', spec=subprocess.Popen) as mock_popen:
       mock_popen.return_value.communicate.side_effect = KeyboardInterrupt()
       with self.assertRaises(KeyboardInterrupt):
         vm_util.IssueCommand(['sleep', '2s'], timeout=None)
+    self.assertFalse(HaveSleepSubprocess())
 
 
 if __name__ == '__main__':