Ensure all phases are stopped

If a phase is started successfully, it needs to be stopped as well. In
most cases when `stop` is called immediately after `start`, this is not
a problem.

Only when something else happens while a phase is runnning and this
something fails, Pungi will deadlock and never exit. This something
could be another phase or just main thread raising an exception.

Fixes: #625
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

bin/pungi-koji

@@ -354,25 +354,25 @@ def run_compose(compose, create_latest_link=True, latest_link_status=None):
     pkgset_phase.start()
     pkgset_phase.stop()
 
-    # BUILDINSTALL phase - start
+    # BUILDINSTALL phase - start, we can run gathering, extra files and
+    # createrepo while buildinstall is in progress.
     buildinstall_phase.start()
 
-    # GATHER phase
+    # If any of the following three phases fail, we must ensure that
+    # buildinstall is stopped. Otherwise the whole process will hang.
+    try:
         gather_phase.start()
         gather_phase.stop()
 
-    # EXTRA_FILES phase
         extrafiles_phase.start()
         extrafiles_phase.stop()
 
-    # CREATEREPO phase
         createrepo_phase.start()
         createrepo_phase.stop()
 
-    # BUILDINSTALL phase
-    # must finish before PRODUCTIMG
-    # must finish before CREATEISO
+    finally:
         buildinstall_phase.stop()
+
     if not buildinstall_phase.skip():
         buildinstall_phase.copy_files()
 
@@ -396,20 +396,12 @@ def run_compose(compose, create_latest_link=True, latest_link_status=None):
             timestamp = pungi.metadata.write_discinfo(compose, arch, variant)
             pungi.metadata.write_media_repo(compose, arch, variant, timestamp)
 
-    # CREATEISO and LIVEIMAGES phases
-    createiso_phase.start()
-    liveimages_phase.start()
-    image_build_phase.start()
-    livemedia_phase.start()
-    ostree_installer_phase.start()
-    osbs_phase.start()
-
-    createiso_phase.stop()
-    liveimages_phase.stop()
-    image_build_phase.stop()
-    livemedia_phase.stop()
-    ostree_installer_phase.stop()
-    osbs_phase.stop()
+    # Start all phases for image artifacts
+    pungi.phases.run_all([createiso_phase,
+                          liveimages_phase,
+                          image_build_phase,
+                          ostree_installer_phase,
+                          osbs_phase])
 
     image_checksum_phase.start()
     image_checksum_phase.stop()

pungi/phases/__init__.py

@@ -31,3 +31,21 @@ from .livemedia_phase import LiveMediaPhase  # noqa
 from .ostree import OSTreePhase  # noqa
 from .ostree_installer import OstreeInstallerPhase  # noqa
 from .osbs import OSBSPhase  # noqa
+
+
+def run_all(phases):
+    """Start and stop all given phases and make them run in parallel.
+
+    This function makes sure that even if one of the phases fails and raises an
+    exception, all the phases will still be correctly stopped.
+
+    If multiple phases fail, a exception from one of them will be raised, but
+    there are no guarantees which one it will be.
+    """
+    if not phases:
+        return
+    phases[0].start()
+    try:
+        run_all(phases[1:])
+    finally:
+        phases[0].stop()

tests/test_phase_base.py

@@ -8,8 +8,8 @@ import sys
 
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
 
-from pungi.phases import base
-from tests.helpers import DummyCompose, PungiTestCase
+from pungi.phases import run_all, base
+from tests.helpers import DummyCompose, PungiTestCase, boom
 
 
 class Phase1(base.ImageConfigMixin, base.PhaseBase):
@@ -69,5 +69,50 @@ class ImageConfigMixinTestCase(PungiTestCase):
         self.assertEqual(resolve_git_url.num, 3, 'Resolver was not called three times')
 
 
+class TestRunAll(unittest.TestCase):
+    def assertFinalized(self, p):
+        self.assertEqual(p.mock_calls, [mock.call.start(), mock.call.stop()])
+
+    def test_calls_stop(self):
+        p1 = mock.Mock()
+        p2 = mock.Mock()
+
+        run_all([p1, p2])
+
+        self.assertFinalized(p1)
+        self.assertFinalized(p2)
+
+    def test_calls_stop_on_failure(self):
+        p1 = mock.Mock()
+        p2 = mock.Mock()
+        p3 = mock.Mock()
+
+        p2.stop.side_effect = boom
+
+        with self.assertRaises(Exception) as ctx:
+            run_all([p1, p2, p3])
+
+        self.assertEqual('BOOM', str(ctx.exception))
+        self.assertFinalized(p1)
+        self.assertFinalized(p2)
+        self.assertFinalized(p3)
+
+    def test_multiple_fail(self):
+        p1 = mock.Mock(name='p1')
+        p2 = mock.Mock(name='p2')
+        p3 = mock.Mock(name='p3')
+
+        p2.stop.side_effect = boom
+        p3.stop.side_effect = boom
+
+        with self.assertRaises(Exception) as ctx:
+            run_all([p1, p2, p3])
+
+        self.assertEqual('BOOM', str(ctx.exception))
+        self.assertFinalized(p1)
+        self.assertFinalized(p2)
+        self.assertFinalized(p3)
+
+
 if __name__ == "__main__":
     unittest.main()