clean up sys.exc_info calls to drop circular refs

gunicorn/_compat.py

@@ -107,11 +107,8 @@ def _wrap_error(exc, mapping, key):
     new_err = new_err_cls(*exc.args)
 
     # raise a new exception with the original traceback
-    if hasattr(exc, '__traceback__'):
-        traceback = exc.__traceback__
-    else:
-        traceback = sys.exc_info()[2]
-    six.reraise(new_err_cls, new_err, traceback)
+    six.reraise(new_err_cls, new_err,
+                exc.__traceback__ if hasattr(exc, '__traceback__') else sys.exc_info()[2])
 
 if PY33:
     import builtins

gunicorn/workers/async.py

@@ -55,13 +55,11 @@ def handle(self, listener, client, addr):
             except StopIteration as e:
                 self.log.debug("Closing connection. %s", e)
             except ssl.SSLError:
-                exc_info = sys.exc_info()
                 # pass to next try-except level
-                six.reraise(exc_info[0], exc_info[1], exc_info[2])
+                six.reraise(*sys.exc_info())
             except EnvironmentError:
-                exc_info = sys.exc_info()
                 # pass to next try-except level
-                six.reraise(exc_info[0], exc_info[1], exc_info[2])
+                six.reraise(*sys.exc_info())
             except Exception as e:
                 self.handle_error(req, client, addr, e)
         except ssl.SSLError as e:

gunicorn/workers/base.py

@@ -134,11 +134,18 @@ def load_wsgi(self):
 
             self.log.exception(e)
 
-            exc_type, exc_val, exc_tb = sys.exc_info()
-            self.reloader.add_extra_file(exc_val.filename)
-
-            tb_string = traceback.format_exc(exc_tb)
-            self.wsgi = util.make_fail_app(tb_string)
+            # fix from PR #1228
+            # storing the traceback into exc_tb will create a circular reference.
+            # per https://docs.python.org/2/library/sys.html#sys.exc_info warning,
+            # delete the traceback after use.
+            try:
+                exc_type, exc_val, exc_tb = sys.exc_info()
+                self.reloader.add_extra_file(exc_val.filename)
+
+                tb_string = traceback.format_exc(exc_tb)
+                self.wsgi = util.make_fail_app(tb_string)
+            finally:
+                del exc_tb
 
     def init_signals(self):
         # reset signaling

gunicorn/workers/gthread.py

@@ -339,9 +339,8 @@ def handle_request(self, req, conn):
                 self.log.debug("Closing connection.")
                 return False
         except EnvironmentError:
-            exc_info = sys.exc_info()
             # pass to next try-except level
-            six.reraise(exc_info[0], exc_info[1], exc_info[2])
+            six.reraise(*sys.exc_info())
         except Exception:
             if resp and resp.headers_sent:
                 # If the requests have already been sent, we should close the

gunicorn/workers/sync.py

@@ -182,9 +182,8 @@ def handle_request(self, listener, req, client, addr):
                 if hasattr(respiter, "close"):
                     respiter.close()
         except EnvironmentError:
-            exc_info = sys.exc_info()
             # pass to next try-except level
-            six.reraise(exc_info[0], exc_info[1], exc_info[2])
+            six.reraise(*sys.exc_info())
         except Exception:
             if resp and resp.headers_sent:
                 # If the requests have already been sent, we should close the