PYTHON-3926 Add more information to connection errors and timeouts

pymongo/common.py

@@ -56,7 +56,6 @@
 if TYPE_CHECKING:
     from pymongo.client_session import ClientSession
 
-
 ORDERED_TYPES: Sequence[Type] = (SON, OrderedDict)
 
 # Defaults until we connect to a server and get updated limits.
@@ -793,7 +792,6 @@ def validate_datetime_conversion(option: Any, value: Any) -> Optional[DatetimeCo
     "waitqueuetimeoutms",
 ]
 
-
 _AUTH_OPTIONS = frozenset(["authmechanismproperties"])
 
 

pymongo/pool.py

@@ -379,7 +379,10 @@ def _truncate_metadata(metadata: MutableMapping[str, Any]) -> None:
 
 
 def _raise_connection_failure(
-    address: Any, error: Exception, msg_prefix: Optional[str] = None
+    address: Any,
+    error: Exception,
+    msg_prefix: Optional[str] = None,
+    timeout_details: Optional[dict[str, float]] = None,
 ) -> NoReturn:
     """Convert a socket.error to ConnectionFailure and raise it."""
     host, port = address
@@ -390,6 +393,8 @@ def _raise_connection_failure(
         msg = f"{host}: {error}"
     if msg_prefix:
         msg = msg_prefix + msg
+    if "configured timeouts" not in msg:
+        msg += format_timeout_details(timeout_details)
     if isinstance(error, socket.timeout):
         raise NetworkTimeout(msg) from error
     elif isinstance(error, SSLError) and "timed out" in str(error):
@@ -407,6 +412,32 @@ def _cond_wait(condition: threading.Condition, deadline: Optional[float]) -> boo
     return condition.wait(timeout)
 
 
+def _get_timeout_details(options: PoolOptions) -> dict[str, float]:
+    details = {}
+    timeout = _csot.get_timeout()
+    socket_timeout = options.socket_timeout
+    connect_timeout = options.connect_timeout
+    if timeout:
+        details["timeoutMS"] = timeout * 1000
+    if socket_timeout and not timeout:
+        details["socketTimeoutMS"] = socket_timeout * 1000
+    if connect_timeout:
+        details["connectTimeoutMS"] = connect_timeout * 1000
+    return details
+
+
+def format_timeout_details(details: Optional[dict[str, float]]) -> str:
+    result = ""
+    if details:
+        result += " (configured timeouts:"
+        for timeout in ["socketTimeoutMS", "timeoutMS", "connectTimeoutMS"]:
+            if timeout in details:
+                result += f" {timeout}: {details[timeout]}ms,"
+        result = result[:-1]
+        result += ")"
+    return result
+
+
 class PoolOptions:
     """Read only connection pool options for a MongoClient.
 
@@ -736,10 +767,15 @@ def apply_timeout(
             rtt = self.connect_rtt
         max_time_ms = timeout - rtt
         if max_time_ms < 0:
+            timeout_details = _get_timeout_details(self.opts)
+            formatted = format_timeout_details(timeout_details)
             # CSOT: raise an error without running the command since we know it will time out.
-            errmsg = f"operation would exceed time limit, remaining timeout:{timeout:.5f} <= network round trip time:{rtt:.5f}"
+            errmsg = f"operation would exceed time limit, remaining timeout:{timeout:.5f} <= network round trip time:{rtt:.5f} {formatted}"
             raise ExecutionTimeout(
-                errmsg, 50, {"ok": 0, "errmsg": errmsg, "code": 50}, self.max_wire_version
+                errmsg,
+                50,
+                {"ok": 0, "errmsg": errmsg, "code": 50},
+                self.max_wire_version,
             )
         if cmd is not None:
             cmd["maxTimeMS"] = int(max_time_ms * 1000)
@@ -1127,7 +1163,8 @@ def _raise_connection_failure(self, error: BaseException) -> NoReturn:
         self.close_conn(reason)
         # SSLError from PyOpenSSL inherits directly from Exception.
         if isinstance(error, (IOError, OSError, SSLError)):
-            _raise_connection_failure(self.address, error)
+            details = _get_timeout_details(self.opts)
+            _raise_connection_failure(self.address, error, timeout_details=details)
         else:
             raise
 
@@ -1251,7 +1288,8 @@ def _configured_socket(address: _Address, options: PoolOptions) -> Union[socket.
         # We raise AutoReconnect for transient and permanent SSL handshake
         # failures alike. Permanent handshake failures, like protocol
         # mismatch, will be turned into ServerSelectionTimeoutErrors later.
-        _raise_connection_failure(address, exc, "SSL handshake failed: ")
+        details = _get_timeout_details(options)
+        _raise_connection_failure(address, exc, "SSL handshake failed: ", timeout_details=details)
     if (
         ssl_context.verify_mode
         and not ssl_context.check_hostname
@@ -1549,7 +1587,8 @@ def connect(self, handler: Optional[_MongoClientErrorHandler] = None) -> Connect
                 )
 
             if isinstance(error, (IOError, OSError, SSLError)):
-                _raise_connection_failure(self.address, error)
+                details = _get_timeout_details(self.opts)
+                _raise_connection_failure(self.address, error, timeout_details=details)
 
             raise
 
@@ -1630,7 +1669,10 @@ def _raise_if_not_ready(self, emit_event: bool) -> None:
                 self.opts._event_listeners.publish_connection_check_out_failed(
                     self.address, ConnectionCheckOutFailedReason.CONN_ERROR
                 )
-            _raise_connection_failure(self.address, AutoReconnect("connection pool paused"))
+            details = _get_timeout_details(self.opts)
+            _raise_connection_failure(
+                self.address, AutoReconnect("connection pool paused"), timeout_details=details
+            )
 
     def _get_conn(self, handler: Optional[_MongoClientErrorHandler] = None) -> Connection:
         """Get or create a Connection. Can raise ConnectionFailure."""

test/test_pooling.py

@@ -23,8 +23,9 @@
 
 from bson.codec_options import DEFAULT_CODEC_OPTIONS
 from bson.son import SON
-from pymongo import MongoClient, message
+from pymongo import MongoClient, message, timeout
 from pymongo.errors import AutoReconnect, ConnectionFailure, DuplicateKeyError
+from pymongo.hello import HelloCompat
 
 sys.path[0:0] = [""]
 
@@ -411,6 +412,84 @@ def find_one():
         # maxConnecting = unbounded: 30+ connections in ~0.140+ seconds
         print(len(pool.conns))
 
+    @client_context.require_failCommand_fail_point
+    def test_csot_timeout_message(self):
+        client = rs_or_single_client(appName="connectionTimeoutApp")
+        # Mock a connection failing due to timeout.
+        mock_connection_timeout = {
+            "configureFailPoint": "failCommand",
+            "mode": "alwaysOn",
+            "data": {
+                "blockConnection": True,
+                "blockTimeMS": 1000,
+                "failCommands": ["find"],
+                "appName": "connectionTimeoutApp",
+            },
+        }
+
+        client.db.t.insert_one({"x": 1})
+
+        with self.fail_point(mock_connection_timeout):
+            with self.assertRaises(Exception) as error:
+                with timeout(0.5):
+                    client.db.t.find_one({"$where": delay(2)})
+
+        self.assertTrue("(configured timeouts: timeoutMS: 500.0ms" in str(error.exception))
+
+    @client_context.require_failCommand_fail_point
+    def test_socket_timeout_message(self):
+        client = rs_or_single_client(socketTimeoutMS=500, appName="connectionTimeoutApp")
+
+        # Mock a connection failing due to timeout.
+        mock_connection_timeout = {
+            "configureFailPoint": "failCommand",
+            "mode": "alwaysOn",
+            "data": {
+                "blockConnection": True,
+                "blockTimeMS": 1000,
+                "failCommands": ["find"],
+                "appName": "connectionTimeoutApp",
+            },
+        }
+
+        client.db.t.insert_one({"x": 1})
+
+        with self.fail_point(mock_connection_timeout):
+            with self.assertRaises(Exception) as error:
+                client.db.t.find_one({"$where": delay(2)})
+
+        self.assertTrue(
+            "(configured timeouts: socketTimeoutMS: 500.0ms, connectTimeoutMS: 20000.0ms)"
+            in str(error.exception)
+        )
+
+    @client_context.require_failCommand_fail_point
+    @client_context.require_version_min(
+        4, 9, 0
+    )  # configureFailPoint does not allow failure on handshake before 4.9, fixed in SERVER-49336
+    def test_connection_timeout_message(self):
+        # Mock a connection failing due to timeout.
+        mock_connection_timeout = {
+            "configureFailPoint": "failCommand",
+            "mode": "alwaysOn",
+            "data": {
+                "blockConnection": True,
+                "blockTimeMS": 1000,
+                "failCommands": [HelloCompat.LEGACY_CMD, "hello"],
+                "appName": "connectionTimeoutApp",
+            },
+        }
+
+        with self.fail_point(mock_connection_timeout):
+            with self.assertRaises(Exception) as error:
+                client = rs_or_single_client(connectTimeoutMS=500, appName="connectionTimeoutApp")
+                client.admin.command("ping")
+
+        self.assertTrue(
+            "(configured timeouts: socketTimeoutMS: 500.0ms, connectTimeoutMS: 500.0ms)"
+            in str(error.exception)
+        )
+
 
 class TestPoolMaxSize(_TestPoolingBase):
     def test_max_pool_size(self):