PYTHON-2596 Include host in error message when connection is closed (mongodb#575)

Use raise from syntax when re-raising exceptions in the pool.

Author: ShaneHarvey

pymongo/network.py

@@ -26,8 +26,7 @@
 from pymongo import helpers, message
 from pymongo.common import MAX_MESSAGE_SIZE
 from pymongo.compression_support import decompress, _NO_COMPRESSION
-from pymongo.errors import (AutoReconnect,
-                            NotMasterError,
+from pymongo.errors import (NotMasterError,
                             OperationFailure,
                             ProtocolError,
                             _OperationCancelled)
@@ -261,7 +260,7 @@ def _receive_data_on_socket(sock_info, length, deadline):
                 continue
             raise
         if chunk_length == 0:
-            raise AutoReconnect("connection closed")
+            raise OSError("connection closed")
 
         bytes_read += chunk_length
 

pymongo/pool.py

@@ -236,16 +236,9 @@ def _raise_connection_failure(address, error, msg_prefix=None):
     if msg_prefix:
         msg = msg_prefix + msg
     if isinstance(error, socket.timeout):
-        raise NetworkTimeout(msg)
-    elif isinstance(error, _SSLError) and 'timed out' in str(error):
-        # CPython 2.7 and PyPy 2.x do not distinguish network
-        # timeouts from other SSLErrors (https://bugs.python.org/issue10272).
-        # Luckily, we can work around this limitation because the phrase
-        # 'timed out' appears in all the timeout related SSLErrors raised
-        # on the above platforms.
-        raise NetworkTimeout(msg)
+        raise NetworkTimeout(msg) from error
     else:
-        raise AutoReconnect(msg)
+        raise AutoReconnect(msg) from error
 
 
 def _cond_wait(condition, deadline):

test/test_client.py

@@ -1568,6 +1568,18 @@ def server_description_count():
             # AssertionError: 4 != 22 within 5 delta (18 difference)
             self.assertAlmostEqual(initial_count, final_count, delta=10)
 
+    @client_context.require_failCommand_fail_point
+    def test_network_error_message(self):
+        client = single_client(retryReads=False)
+        self.addCleanup(client.close)
+        client.admin.command('ping')  # connect
+        with self.fail_point({'mode': {'times': 1},
+                              'data': {'closeConnection': True,
+                                       'failCommands': ['find']}}):
+            expected = '%s:%s: connection closed' % client.address
+            with self.assertRaisesRegex(AutoReconnect, expected):
+                client.pymongo_test.test.find_one({})
+
 
 class TestExhaustCursor(IntegrationTest):
     """Test that clients properly handle errors from exhaust cursors."""