Fixed the LDAP authentication issue for the simultaneous login attempts.

web/pgadmin/authenticate/__init__.py

@@ -12,6 +12,7 @@
 import config
 import copy
 import functools
+from threading import Lock
 
 from flask import current_app, flash, Response, request, url_for, \
     session, redirect, render_template
@@ -35,6 +36,19 @@ auth_obj = None
 _URL_WITH_NEXT_PARAM = "{0}?next={1}"
 
 
+class AuthLocker:
+    """Implementing lock while authentication."""
+    lock = Lock()
+
+    def __enter__(self):
+        self.lock.acquire()
+        return self
+
+    def __exit__(self, type, value, traceback):
+        if self.lock.locked():
+            self.lock.release()
+
+
 def get_logout_url() -> str:
     """
     Returns the logout url based on the current authentication method.
@@ -83,6 +97,14 @@ def login():
     Entry point for all the authentication sources.
     The user input will be validated and authenticated.
     """
+    with AuthLocker():
+        return _login()
+
+
+def _login():
+    """
+    Internal authentication process locked by a mutex.
+    """
     form = _security.forms.get('login_form').cls(request.form)
     if OAUTH2 in config.AUTHENTICATION_SOURCES \
             and 'oauth2_button' in request.form: