Fix a possible receive timeout

This patch fixes a possible receive timeout caused by a slow response from the
driver agent. For example if the database is very slow.

Change-Id: I9079030a5fef9dc44da242adab3c568666777451

octavia_lib/api/drivers/driver_lib.py

@@ -58,11 +58,19 @@ class DriverLibrary():
 
     def _recv(self, sock):
         size_str = b''
-        char = sock.recv(1)
         begin = time.time()
-        while char != b'\n':
-            size_str += char
-            char = sock.recv(1)
+        while True:
+            try:
+                char = sock.recv(1)
+            except socket.timeout:
+                # We could have an overloaded DB and the query may take too
+                # long, so as long as DRIVER_AGENT_TIMEOUT hasn't expired,
+                # let's keep trying while not blocking everything.
+                pass
+            else:
+                if char == b'\n':
+                    break
+                size_str += char
             if time.time() - begin > DRIVER_AGENT_TIMEOUT:
                 raise driver_exceptions.DriverAgentTimeout(
                     fault_string=('The driver agent did not respond in {} '

octavia_lib/tests/unit/api/drivers/test_driver_lib.py

@@ -45,7 +45,7 @@ class TestDriverLib(base.TestCase):
     @mock.patch('builtins.memoryview')
     def test_recv(self, mock_memoryview):
         mock_socket = mock.MagicMock()
-        mock_socket.recv.side_effect = [b'1', b'\n', b'2', b'\n', b'3', b'\n']
+        mock_socket.recv.side_effect = [b'1', b'\n', b'2', b'3', b'\n']
         mock_socket.recv_into.return_value = 1
         mv_mock = mock.MagicMock()
         mock_memoryview.return_value = mv_mock

releasenotes/notes/Fix-possible-receive-timeout-error-f6d2454c48eb10cf.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed a possible receive timeout if the driver agent didn't respond inside
+    five seconds. For example if you have a very slow database.