Improve the approach we use to determine Python 3 system lib path

CHANGELOG.rst

@@ -28,7 +28,7 @@ Fixed
   correctly.
 
   In such scenario, package / module was incorrectly loaded from Python 2 site-packages instead of
-  Python 3 standard library which broke such packs. (bug fix) #4658
+  Python 3 standard library which broke such packs. (bug fix) #4658 #4674
 
 3.0.0 - April 18, 2019
 ----------------------

conf/st2.conf.sample

@@ -14,16 +14,18 @@ actions_pool_size = 60
 python_runner_log_level = DEBUG
 # Internal pool size for dispatcher used by workflow actions.
 workflows_pool_size = 40
+# Prefix for Python 3 installation (e.g. /opt/python3.6). If not specified, it tries to find Python 3 libraries in /usr/lib and /usr/local/lib.
+python3_prefix = None
 # Virtualenv binary which should be used to create pack virtualenvs.
 virtualenv_binary = /usr/bin/virtualenv
-# Python 3 binary which will be used by Python actions for packs which use Python 3 virtual environment
+# Python 3 binary which will be used by Python actions for packs which use Python 3 virtual environment.
 python3_binary = /usr/bin/python3
-# location of the logging.conf file
-logging = /etc/st2/logging.actionrunner.conf
-# True to store and stream action output (stdout and stderr) in real-time.
-stream_output = True
 # List of virtualenv options to be passsed to "virtualenv" command that creates pack virtualenv.
 virtualenv_opts = --system-site-packages # comma separated list allowed here.
+# True to store and stream action output (stdout and stderr) in real-time.
+stream_output = True
+# location of the logging.conf file
+logging = /etc/st2/logging.actionrunner.conf
 # Python binary which will be used by Python actions.
 python_binary = /usr/bin/python
 

st2common/st2common/config.py

@@ -358,7 +358,11 @@ def register_opts(ignore_errors=False):
         cfg.StrOpt(
             'python3_binary', default=default_python3_bin_path,
             help='Python 3 binary which will be used by Python actions for packs which '
-                 'use Python 3 virtual environment'),
+                 'use Python 3 virtual environment.'),
+        cfg.StrOpt(
+            'python3_prefix', default=None,
+            help='Prefix for Python 3 installation (e.g. /opt/python3.6). If not specified, it '
+                 'tries to find Python 3 libraries in /usr/lib and /usr/local/lib.'),
         cfg.StrOpt(
             'virtualenv_binary', default=default_virtualenv_bin_path,
             help='Virtualenv binary which should be used to create pack virtualenvs.'),

st2common/st2common/util/sandboxing.py

@@ -162,20 +162,32 @@ def get_sandbox_python_path_for_python_action(pack, inherit_from_parent=True,
                                                        'site-packages')
 
         # Work around to make sure we also add system lib dir to PYTHONPATH and not just virtualenv
-        # one
-        # NOTE: abc.py is always available in base lib directory which is symlinked to virtualenv
-        # lib directory
-        abc_module_path = os.path.join(python3_lib_directory, 'abc.py')
-        link_path = os.path.realpath(abc_module_path)
-        python3_system_lib_directory = os.path.dirname(link_path)
-
-        if not os.path.exists(python3_system_lib_directory):
+        # one (e.g. /usr/lib/python3.6)
+        # NOTE: We can't simply use sys.prefix dir since it will be set to /opt/stackstorm/st2
+
+        system_prefix_dirs = []
+        # Take custom prefix into account (if specified)
+        if cfg.CONF.actionrunner.python3_prefix:
+            system_prefix_dirs.append(cfg.CONF.actionrunner.python3_prefix)
+
+        # By default, Python libs are installed either in /usr/lib/python3.x or
+        # /usr/local/lib/python3.x
+        system_prefix_dirs.extend(['/usr/lib', '/usr/local/lib'])
+
+        for system_prefix_dir in system_prefix_dirs:
+            python3_system_lib_directory = os.path.join(system_prefix_dir,
+                                                        virtualenv_directories[0])
+
+            if os.path.exists(python3_system_lib_directory):
+                break
+
+        if not python3_system_lib_directory or not os.path.exists(python3_system_lib_directory):
             python3_system_lib_directory = None
 
         full_sandbox_python_path = []
 
         # NOTE: Order here is very important for imports to function correctly
-        if python3_lib_directory:
+        if python3_system_lib_directory:
             full_sandbox_python_path.append(python3_system_lib_directory)
 
         full_sandbox_python_path.append(python3_lib_directory)

st2common/tests/unit/test_util_sandboxing.py

@@ -146,7 +146,6 @@ def test_get_sandbox_python_path_for_python_action_python2_used_for_venv(self,
     @mock.patch('os.path.exists', mock.Mock(return_value=True))
     @mock.patch('os.path.isdir', mock.Mock(return_value=True))
     @mock.patch('os.listdir', mock.Mock(return_value=['python3.6']))
-    @mock.patch('os.path.realpath', mock.Mock(return_value='/usr/lib/python3.6/abc.py'))
     @mock.patch('st2common.util.sandboxing.get_python_lib')
     @mock.patch('st2common.util.sandboxing.get_pack_base_path',
                 mock.Mock(return_value='/tmp/packs/dummy_pack'))
@@ -165,6 +164,8 @@ def test_get_sandbox_python_path_for_python_action_python3_used_for_venv(self,
         self.assertEqual(len(split), 4)
 
         # First entry should be system lib/python3 dir
+        self.assertTrue('/usr/lib/python3.6' in split[0])
+
         # Second entry should be lib/python3 dir from venv
         self.assertTrue('virtualenvs/dummy_pack/lib/python3.6' in split[1])
 
@@ -207,3 +208,27 @@ def test_get_sandbox_python_path_for_python_action_python3_used_for_venv(self,
                     '/tmp/packs/dummy_pack/actions/lib/::/data/test1:/data/test2:'
                     '%s/virtualenvtest' % (sys.prefix))
         self.assertEqual(python_path, expected)
+
+        # Custom prefix specified in the config
+        cfg.CONF.set_override(name='python3_prefix', override='/opt/lib',
+                              group='actionrunner')
+
+        # No inheritance
+        python_path = get_sandbox_python_path_for_python_action(pack='dummy_pack',
+                                                                inherit_from_parent=False,
+                                                                inherit_parent_virtualenv=False)
+
+        split = python_path.strip(':').split(':')
+        self.assertEqual(len(split), 4)
+
+        # First entry should be system lib/python3 dir
+        self.assertTrue('/opt/lib/python3.6' in split[0])
+
+        # Second entry should be lib/python3 dir from venv
+        self.assertTrue('virtualenvs/dummy_pack/lib/python3.6' in split[1])
+
+        # Third entry should be python3 site-packages dir from venv
+        self.assertTrue('virtualenvs/dummy_pack/lib/python3.6/site-packages' in split[2])
+
+        # Fourth entry should be actions/lib dir from pack root directory
+        self.assertTrue('packs/dummy_pack/actions/lib/' in split[3])