fix(utils): report free port search exhaustion

swift/utils/utils.py

@@ -295,15 +295,20 @@ def find_node_ip() -> Optional[str]:
 def find_free_port(start_port: Optional[int] = None, retry: int = 100) -> int:
     if start_port is None:
         start_port = 0
-    for port in range(start_port, start_port + retry):
+    if not 0 <= start_port <= 65535:
+        raise ValueError(f'Invalid start_port: {start_port}')
+    if retry < 1:
+        raise ValueError(f'Invalid retry: {retry}')
+
+    stop_port = min(start_port + retry, 65536)
+    for port in range(start_port, stop_port):
         with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
             try:
                 sock.bind(('', port))
-                port = sock.getsockname()[1]
-                break
             except OSError:
-                pass
-    return port
+                continue
+            return sock.getsockname()[1]
+    raise OSError(f'No free port found in range [{start_port}, {stop_port})')
 
 
 def copy_files_by_pattern(source_dir, dest_dir, patterns, exclude_patterns=None):

tests/utils/test_port_utils.py

@@ -0,0 +1,42 @@
+import unittest
+from unittest.mock import call, patch
+
+from swift.utils import find_free_port
+
+
+class TestFindFreePort(unittest.TestCase):
+
+    @patch('swift.utils.utils.socket.socket')
+    def test_returns_next_available_port(self, socket_cls):
+        sock = socket_cls.return_value.__enter__.return_value
+        sock.bind.side_effect = [OSError('occupied'), None]
+        sock.getsockname.return_value = ('0.0.0.0', 30001)
+
+        port = find_free_port(30000, retry=2)
+
+        self.assertEqual(port, 30001)
+        self.assertEqual(sock.bind.call_args_list, [call(('', 30000)), call(('', 30001))])
+
+    @patch('swift.utils.utils.socket.socket')
+    def test_raises_when_candidate_range_is_exhausted(self, socket_cls):
+        sock = socket_cls.return_value.__enter__.return_value
+        sock.bind.side_effect = OSError('occupied')
+
+        with self.assertRaisesRegex(OSError, r'\[30000, 30003\)'):
+            find_free_port(30000, retry=3)
+
+        self.assertEqual(sock.bind.call_count, 3)
+
+    @patch('swift.utils.utils.socket.socket')
+    def test_does_not_scan_past_max_port(self, socket_cls):
+        sock = socket_cls.return_value.__enter__.return_value
+        sock.bind.side_effect = OSError('occupied')
+
+        with self.assertRaisesRegex(OSError, r'\[65535, 65536\)'):
+            find_free_port(65535, retry=2)
+
+        sock.bind.assert_called_once_with(('', 65535))
+
+
+if __name__ == '__main__':
+    unittest.main()