Lock global vars during initialization for thread safety

Acquire a lock before initializing global vars to ensure thread safety. Otherwise, it is possible race can occur between multiple threads when initializing the vars.

Author: m4dcoder

CHANGELOG.rst

@@ -1,6 +1,15 @@
 Changelog
 =========
 
+In Progress
+-----------
+
+Fixed
+~~~~~
+
+* Warn users when there is a loop and no start task identified. (bug fix)
+* Lock global variables during initialization to make them thread safe. (bug fix)
+
 1.1.1
 -----
 

orquesta/expressions/base.py

@@ -17,6 +17,7 @@
 import logging
 import re
 import six
+import threading
 
 from stevedore import extension
 
@@ -27,6 +28,7 @@
 LOG = logging.getLogger(__name__)
 
 _EXP_EVALUATORS = None
+_EXP_EVALUATORS_LOCK = threading.Lock()
 _EXP_EVALUATOR_NAMESPACE = "orquesta.expressions.evaluators"
 
 
@@ -73,14 +75,18 @@ def get_evaluator(language):
 
 def get_evaluators():
     global _EXP_EVALUATORS
+    global _EXP_EVALUATORS_LOCK
 
-    if _EXP_EVALUATORS is None:
-        _EXP_EVALUATORS = {}
+    with _EXP_EVALUATORS_LOCK:
+        if _EXP_EVALUATORS is None:
+            _EXP_EVALUATORS = {}
 
-        mgr = extension.ExtensionManager(namespace=_EXP_EVALUATOR_NAMESPACE, invoke_on_load=False)
+            mgr = extension.ExtensionManager(
+                namespace=_EXP_EVALUATOR_NAMESPACE, invoke_on_load=False
+            )
 
-        for name in mgr.names():
-            _EXP_EVALUATORS[name] = get_evaluator(name)
+            for name in mgr.names():
+                _EXP_EVALUATORS[name] = get_evaluator(name)
 
     return _EXP_EVALUATORS
 

orquesta/expressions/functions/base.py

@@ -12,23 +12,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import threading
+
 from stevedore import extension
 
 
 _EXP_FUNC_CATALOG = None
+_EXP_FUNC_CATALOG_LOCK = threading.Lock()
 
 
 def load():
     global _EXP_FUNC_CATALOG
+    global _EXP_FUNC_CATALOG_LOCK
 
-    if _EXP_FUNC_CATALOG is None:
-        _EXP_FUNC_CATALOG = {}
+    with _EXP_FUNC_CATALOG_LOCK:
+        if _EXP_FUNC_CATALOG is None:
+            _EXP_FUNC_CATALOG = {}
 
-        mgr = extension.ExtensionManager(
-            namespace="orquesta.expressions.functions", invoke_on_load=False
-        )
+            mgr = extension.ExtensionManager(
+                namespace="orquesta.expressions.functions", invoke_on_load=False
+            )
 
-        for name in mgr.names():
-            _EXP_FUNC_CATALOG[name] = mgr[name].plugin
+            for name in mgr.names():
+                _EXP_FUNC_CATALOG[name] = mgr[name].plugin
 
     return _EXP_FUNC_CATALOG