Merge "NSXv3: Move away from locking in cert provider"

vmware_nsx/plugins/nsx_v3/utils.py

@@ -37,11 +37,13 @@ LOG = logging.getLogger(__name__)
 class DbCertProvider(client_cert.ClientCertProvider):
     """Write cert data from DB to file and delete after use
 
-       Since several connections may use same filename simultaneously,
-       this class maintains refcount to write/delete the file only once
+       New file with random filename is created for each thread. This
+       is not most efficient, but the safest way to avoid race conditions,
+       since backend connections can occur both before and after neutron
+       fork.
     """
     EXPIRATION_ALERT_DAYS = 30          # days prior to expiration
-    lock = threading.Lock()
+    _thread_local = threading.local()
 
     def __init__(self):
         # Note: we cannot initialize filename here, because this call
@@ -54,11 +56,6 @@ class DbCertProvider(client_cert.ClientCertProvider):
         super(DbCertProvider, self).__init__(None)
         random.seed()
 
-        with self.lock:
-            # Initialize refcount if other threads did not do it already
-            if not hasattr(self, 'refcount'):
-                self.refcount = 0
-
     def _check_expiration(self, expires_in_days):
         if expires_in_days > self.EXPIRATION_ALERT_DAYS:
             return
@@ -72,16 +69,10 @@ class DbCertProvider(client_cert.ClientCertProvider):
                         expires_in_days)
 
     def __enter__(self):
-        with self.lock:
-            self.refcount += 1
-
-            if self.refcount > 1:
-                # The file was already created and not yet deleted, use it
-                return self
-
             # No certificate file available - need to create one
             # Choose a random filename to contain the certificate
-            self._filename = '/tmp/.' + str(random.randint(1, 10000000))
+            self._thread_local._filename = '/tmp/.' + str(
+                random.randint(1, 10000000))
 
             try:
                 context = q_context.get_admin_context()
@@ -95,15 +86,15 @@ class DbCertProvider(client_cert.ClientCertProvider):
                         msg = _("Unable to load from nsx-db")
                         raise nsx_exc.ClientCertificateException(err_msg=msg)
 
-                    if not os.path.exists(os.path.dirname(self._filename)):
-                        if len(os.path.dirname(self._filename)) > 0:
-                            os.makedirs(os.path.dirname(self._filename))
-                    cert_manager.export_pem(self._filename)
+                    filename = self._thread_local._filename
+                    if not os.path.exists(os.path.dirname(filename)):
+                        if len(os.path.dirname(filename)) > 0:
+                            os.makedirs(os.path.dirname(filename))
+                    cert_manager.export_pem(filename)
 
                     expires_in_days = cert_manager.expires_in_days()
                     self._check_expiration(expires_in_days)
             except Exception as e:
-                # refcount has to be 1 here
                 self._on_exit()
                 raise e
 
@@ -111,23 +102,17 @@ class DbCertProvider(client_cert.ClientCertProvider):
             return self
 
     def _on_exit(self):
-        self.refcount -= 1
-
-        if self.refcount == 0:
-            # I am the last user of this file
-            if os.path.isfile(self._filename):
-                os.remove(self._filename)
+        if os.path.isfile(self._thread_local._filename):
+            os.remove(self._thread_local._filename)
             LOG.debug("Deleted client certificate file")
 
-            self._filename = None
+        self._thread_local._filename = None
 
     def __exit__(self, type, value, traceback):
-        with self.lock:
         self._on_exit()
 
     def filename(self):
-        with self.lock:
-            return self._filename
+        return self._thread_local._filename
 
 
 def get_client_cert_provider():