fix: add threading lock to AuthManager config mutations (#1226)

tests/test_auth_config_lock_concurrency.py

@@ -0,0 +1,198 @@
+"""Concurrency stress tests for AuthManager._config_lock.
+
+Verifies that concurrent create/delete/rename operations don't lose data
+or corrupt auth.json. If someone removes the lock, these tests should fail
+with missing users or assertion errors.
+"""
+
+import json
+import sys
+import threading
+import time
+from concurrent.futures import ThreadPoolExecutor, as_completed
+
+import pytest
+
+
+def _fresh_auth_manager(tmp_path):
+    sys.modules.pop("core.auth", None)
+    if "core" in sys.modules and hasattr(sys.modules["core"], "auth"):
+        delattr(sys.modules["core"], "auth")
+    from core.auth import AuthManager
+
+    return AuthManager(str(tmp_path / "auth.json"))
+
+
+class TestConcurrentCreateUser:
+    """Concurrent create_user calls must not lose accounts."""
+
+    def test_parallel_creates_no_lost_users(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        num_users = 50
+
+        def create(i):
+            return mgr.create_user(f"user{i}", f"password{i}")
+
+        with ThreadPoolExecutor(max_workers=10) as pool:
+            futures = [pool.submit(create, i) for i in range(num_users)]
+            results = [f.result() for f in as_completed(futures)]
+
+        assert all(results), "Some create_user calls returned False unexpectedly"
+        assert len(mgr.users) == num_users
+
+        mgr2 = _fresh_auth_manager(tmp_path)
+        mgr2.auth_path = mgr.auth_path
+        mgr2._load()
+        assert len(mgr2.users) == num_users
+
+    def test_parallel_creates_same_username_only_one_wins(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        num_attempts = 20
+
+        def create(_):
+            return mgr.create_user("contested", "password123")
+
+        with ThreadPoolExecutor(max_workers=10) as pool:
+            futures = [pool.submit(create, i) for i in range(num_attempts)]
+            results = [f.result() for f in as_completed(futures)]
+
+        assert results.count(True) == 1
+        assert results.count(False) == num_attempts - 1
+        assert len(mgr.users) == 1
+
+
+class TestConcurrentDeleteUser:
+    """Concurrent deletes must not corrupt state."""
+
+    def test_parallel_deletes_no_corruption(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        mgr.create_user("admin", "adminpw", is_admin=True)
+        num_users = 30
+        for i in range(num_users):
+            mgr.create_user(f"target{i}", f"pw{i}")
+
+        assert len(mgr.users) == num_users + 1
+
+        def delete(i):
+            return mgr.delete_user(f"target{i}", "admin")
+
+        with ThreadPoolExecutor(max_workers=10) as pool:
+            futures = [pool.submit(delete, i) for i in range(num_users)]
+            results = [f.result() for f in as_completed(futures)]
+
+        assert all(results)
+        assert len(mgr.users) == 1
+        with open(mgr.auth_path, "r") as f:
+            data = json.load(f)
+        assert len(data["users"]) == 1
+        assert "admin" in data["users"]
+
+
+class TestConcurrentRenameUser:
+    """Concurrent renames must not lose or duplicate users."""
+
+    def test_parallel_renames_no_lost_users(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        mgr.create_user("admin", "adminpw", is_admin=True)
+        num_users = 20
+        for i in range(num_users):
+            mgr.create_user(f"old{i}", f"pw{i}")
+
+        def rename(i):
+            return mgr.rename_user(f"old{i}", f"new{i}", "admin")
+
+        with ThreadPoolExecutor(max_workers=10) as pool:
+            futures = [pool.submit(rename, i) for i in range(num_users)]
+            results = [f.result() for f in as_completed(futures)]
+
+        assert all(results)
+        for i in range(num_users):
+            assert f"new{i}" in mgr.users
+            assert f"old{i}" not in mgr.users
+
+        assert len(mgr.users) == num_users + 1
+
+
+class TestConcurrentMixedOperations:
+    """Mixed create/delete/rename at the same time."""
+
+    def test_mixed_operations_no_corruption(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        mgr.create_user("admin", "adminpw", is_admin=True)
+
+        for i in range(20):
+            mgr.create_user(f"existing{i}", f"pw{i}")
+
+        def create_batch():
+            for i in range(20):
+                mgr.create_user(f"newuser{i}", f"pw{i}")
+
+        def delete_batch():
+            for i in range(10):
+                mgr.delete_user(f"existing{i}", "admin")
+
+        def rename_batch():
+            for i in range(10, 20):
+                mgr.rename_user(f"existing{i}", f"renamed{i}", "admin")
+
+        threads = [
+            threading.Thread(target=create_batch),
+            threading.Thread(target=delete_batch),
+            threading.Thread(target=rename_batch),
+        ]
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+
+        assert "admin" in mgr.users
+        for i in range(10):
+            assert f"existing{i}" not in mgr.users
+        for i in range(10, 20):
+            assert f"renamed{i}" in mgr.users
+            assert f"existing{i}" not in mgr.users
+        for i in range(20):
+            assert f"newuser{i}" in mgr.users
+
+        with open(mgr.auth_path, "r") as f:
+            data = json.load(f)
+        assert set(data["users"].keys()) == set(mgr.users.keys())
+
+
+class TestDiskConsistency:
+    """Verify auth.json is never in a corrupt state during concurrent writes."""
+
+    def test_file_always_valid_json_during_concurrent_ops(self, tmp_path):
+        mgr = _fresh_auth_manager(tmp_path)
+        mgr.create_user("admin", "adminpw", is_admin=True)
+
+        stop_event = threading.Event()
+        corruption_found = []
+
+        def reader():
+            while not stop_event.is_set():
+                try:
+                    with open(mgr.auth_path, "r") as f:
+                        content = f.read()
+                    json.loads(content)
+                except json.JSONDecodeError as e:
+                    corruption_found.append(str(e))
+                    break
+                except FileNotFoundError:
+                    pass
+                time.sleep(0.001)
+
+        def writer():
+            for i in range(50):
+                mgr.create_user(f"stress{i}", f"pw{i}")
+
+        reader_thread = threading.Thread(target=reader)
+        writer_thread = threading.Thread(target=writer)
+
+        reader_thread.start()
+        writer_thread.start()
+        writer_thread.join()
+        stop_event.set()
+        reader_thread.join()
+
+        assert not corruption_found, f"Corrupt JSON detected: {corruption_found[0]}"