Merge pull request #1 from redshiftzero/multithread-singleton

synchronize singleton creation using threading.Lock() in __call__
freedomofpress · Dec 2, 2019 · 667e8f1 · 667e8f1
2 parents 5c81deb + 096a57d
commit 667e8f1
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/oqubeslogging.py b/oqubeslogging.py
@@ -1,13 +1,16 @@
 from logging import StreamHandler
 from subprocess import Popen, PIPE
+import threading
 
 
 class Singleton(type):
     _ins = {}
+    _lock = threading.Lock()
 
     def __call__(cls, *args, **kwargs):
-        if cls not in cls._ins:
-            cls._ins[cls] = (super(Singleton, cls).__call__(*args, **kwargs), args)
+        with cls._lock:  # First thread that gets here creates the instance
+            if cls not in cls._ins:
+                cls._ins[cls] = (super(Singleton, cls).__call__(*args, **kwargs), args)
 
         if len(args) > 1:
             if args != cls._ins[cls][1]: