avocado.job: Run avocado tests isolated in sub processes

In order to ensure avocado tests won't mess with the
main avocado process' environment, execute them in
forked subprocesses. If the test params have a
'timeout' attribute, use it as the timeout param
of the .join() multiprocess method, allowing the
subprocesses to be killed after timeout seconds if
they did not complete.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/job.py

@@ -19,7 +19,9 @@ Module that describes a sequence of automated test operations.
 
 import imp
 import logging
+import multiprocessing
 import os
+import signal
 import sys
 import traceback
 import uuid
@@ -85,6 +87,25 @@ class TestRunner(object):
                                            job=self.job)
         return test_instance
 
+    def run_test(self, instance, queue):
+        """
+        Run a test instance in a subprocess.
+
+        :param instance: Test instance.
+        :type instance: :class:`avocado.test.Test` instance.
+        :param queue: Multiprocess queue.
+        :type queue: :class`multiprocessing.Queue` instance.
+        """
+        def timeout_handler(signum, frame):
+            e_msg = "Timeout reached waiting for %s to end" % instance
+            raise exceptions.TestTimeoutError(e_msg)
+
+        signal.signal(signal.SIGTERM, timeout_handler)
+        try:
+            instance.run_avocado()
+        finally:
+            queue.put(instance)
+
     def run(self, params_list):
         """
         Run one or more tests and report with test result.
@@ -95,10 +116,29 @@ class TestRunner(object):
         """
         failures = []
         self.result.start_tests()
+        q = multiprocessing.Queue()
         for params in params_list:
             test_instance = self.load_test(params)
             self.result.start_test(test_instance)
-            test_instance.run_avocado()
+            p = multiprocessing.Process(target=self.run_test,
+                                        args=(test_instance, q,))
+            p.start()
+            # The test timeout can come from:
+            # 1) Test params dict (params)
+            # 2) Test default params dict (test_instance.params.timeout)
+            timeout = params.get('timeout')
+            if timeout is None:
+                if hasattr(test_instance.params, 'timeout'):
+                    timeout = test_instance.params.timeout
+            if timeout is not None:
+                timeout = float(timeout)
+            # Wait for the test to end for [timeout] s
+            p.join(timeout)
+            # If there's no exit code, the test is still running.
+            # It must be terminated.
+            if p.exitcode is None:
+                p.terminate()
+            test_instance = q.get()
             self.result.check_test(test_instance)
             if not status.mapping[test_instance.status]:
                 failures.append(test_instance.name)