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PYTHON-5875 - Wrap SSL handshake errors before labeling with overload #2866

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PYTHON-5875 - Wrap SSL handshake errors before labeling with overload #2866

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PYTHON-5875 - Wrap SSL handshake errors before labeling with overload
NoahStapp Jun 10, 2026
4a1e2e6
Merge branch 'master' into PYTHON-5875
NoahStapp Jun 11, 2026
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10 changes: 8 additions & 2 deletions pymongo/asynchronous/pool.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1061,10 +1061,16 @@ async def connect(self, handler: Optional[_MongoClientErrorHandler] = None) -> A
reason=_verbose_connection_error_reason(ConnectionClosedReason.ERROR),
error=ConnectionClosedReason.ERROR,
)
self._handle_connection_error(error)
if isinstance(error, (IOError, OSError, *SSLErrors)):
details = _get_timeout_details(self.opts)
_raise_connection_failure(self.address, error, timeout_details=details)
# Wrap to AutoReconnect/NetworkTimeout BEFORE labeling so the
# SystemOverloadedError label lands on the propagated exception.
try:
_raise_connection_failure(self.address, error, timeout_details=details)
except (AutoReconnect, NetworkTimeout) as wrapped:
self._handle_connection_error(wrapped)
raise
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self._handle_connection_error(error)
Comment on lines 1064 to +1073

@NoahStapp NoahStapp Jun 11, 2026 •
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Per the relevant part of the CMAP spec, the only types of establishment errors that MUST be excluded from having the backpressure labels applied are the following:

  1. DNS lookup failures: excluded by the socket.gaierror check in _handle_connection_error.
  2. Non-I/O TLS errors (certificate validation, hostname mismatch failures): excluded the _CertificateError, SSLErrors check in `_handle_connection_errors.
  3. SOCKS5 errors: PyMongo does not currently support SOCKS5.

This change then correctly addresses a bug in the driver where errors that MUST be labeled as possible overload errors are not.

raise

conn = AsyncConnection(networking_interface, self, self.address, conn_id, self.is_sdam) # type: ignore[arg-type]
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10 changes: 8 additions & 2 deletions pymongo/synchronous/pool.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1057,10 +1057,16 @@ def connect(self, handler: Optional[_MongoClientErrorHandler] = None) -> Connect
reason=_verbose_connection_error_reason(ConnectionClosedReason.ERROR),
error=ConnectionClosedReason.ERROR,
)
self._handle_connection_error(error)
if isinstance(error, (IOError, OSError, *SSLErrors)):
details = _get_timeout_details(self.opts)
_raise_connection_failure(self.address, error, timeout_details=details)
# Wrap to AutoReconnect/NetworkTimeout BEFORE labeling so the
# SystemOverloadedError label lands on the propagated exception.
try:
_raise_connection_failure(self.address, error, timeout_details=details)
except (AutoReconnect, NetworkTimeout) as wrapped:
self._handle_connection_error(wrapped)
raise
self._handle_connection_error(error)
raise

conn = Connection(networking_interface, self, self.address, conn_id, self.is_sdam) # type: ignore[arg-type]
Expand Down
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