Connection errors to unauthenticated telemetry endpoint

src/databricks/sql/client.py

@@ -21,7 +21,10 @@
     InterfaceError,
     NotSupportedError,
     ProgrammingError,
+    AuthenticationError,
+    ConnectionError,
 )
+from urllib3.exceptions import MaxRetryError
 from databricks.sql.thrift_api.TCLIService import ttypes
 from databricks.sql.thrift_backend import ThriftBackend
 from databricks.sql.utils import (
@@ -242,9 +245,18 @@ def read(self) -> Optional[OAuthToken]:
         self.disable_pandas = kwargs.get("_disable_pandas", False)
         self.lz4_compression = kwargs.get("enable_query_result_lz4_compression", True)
 
-        auth_provider = get_python_sql_connector_auth_provider(
-            server_hostname, **kwargs
-        )
+        try:
+            auth_provider = get_python_sql_connector_auth_provider(
+                server_hostname, **kwargs
+            )
+        except Exception as e:
+            raise AuthenticationError(
+                message=f"Failed to create authentication provider: {str(e)}",
+                host_url=server_hostname,
+                http_path=http_path,
+                port=self.port,
+                original_exception=e,
+            ) from e
 
         self.server_telemetry_enabled = True
         self.client_telemetry_enabled = kwargs.get("enable_telemetry", False)
@@ -282,20 +294,33 @@ def read(self) -> Optional[OAuthToken]:
             tls_client_cert_key_password=kwargs.get("_tls_client_cert_key_password"),
         )
 
-        self.thrift_backend = ThriftBackend(
-            self.host,
-            self.port,
-            http_path,
-            (http_headers or []) + base_headers,
-            auth_provider,
-            ssl_options=self._ssl_options,
-            _use_arrow_native_complex_types=_use_arrow_native_complex_types,
-            **kwargs,
-        )
+        try:
+            self.thrift_backend = ThriftBackend(
+                self.host,
+                self.port,
+                http_path,
+                (http_headers or []) + base_headers,
+                auth_provider,
+                ssl_options=self._ssl_options,
+                _use_arrow_native_complex_types=_use_arrow_native_complex_types,
+                **kwargs,
+            )
+
+            self._open_session_resp = self.thrift_backend.open_session(
+                session_configuration, catalog, schema
+            )
+        except (RequestError, MaxRetryError, MaxRetryDurationError) as e:
+            raise
+        except Exception as e:
+            raise ConnectionError(
+                message=f"Failed to establish connection: {str(e)}",
+                host_url=self.host,
+                http_path=http_path,
+                port=self.port,
+                user_agent=useragent_header,
+                original_exception=e,
+            ) from e
 
-        self._open_session_resp = self.thrift_backend.open_session(
-            session_configuration, catalog, schema
-        )
         self._session_handle = self._open_session_resp.sessionHandle
         self.protocol_version = self.get_protocol_version(self._open_session_resp)
         self.use_cloud_fetch = kwargs.get("use_cloud_fetch", True)

src/databricks/sql/exc.py

@@ -22,10 +22,29 @@ def __init__(
 
         error_name = self.__class__.__name__
         if session_id_hex:
+            # Normal case: we have a session, send to regular telemetry client
             telemetry_client = TelemetryClientFactory.get_telemetry_client(
                 session_id_hex
             )
             telemetry_client.export_failure_log(error_name, self.message)
+        elif (
+            isinstance(self, (ConnectionError, AuthenticationError))
+            and "host_url" in self.context
+        ):
+            # Connection error case: no session but we should still send telemetry
+            self._send_connection_error_telemetry(error_name)
+
+    def _send_connection_error_telemetry(self, error_name):
+        """Send connection error telemetry to unauthenticated endpoint"""
+
+        TelemetryClientFactory.send_connection_error_telemetry(
+            error_name=error_name,
+            error_message=self.message or str(self),
+            host_url=self.context["host_url"],
+            http_path=self.context.get("http_path", ""),
+            port=self.context.get("port", 443),
+            user_agent=self.context.get("user_agent"),
+        )
 
     def __str__(self):
         return self.message
@@ -126,3 +145,46 @@ class SessionAlreadyClosedError(RequestError):
 
 class CursorAlreadyClosedError(RequestError):
     """Thrown if CancelOperation receives a code 404. ThriftBackend should gracefully proceed as this is expected."""
+
+
+class ConnectionError(OperationalError):
+    """Thrown when connection to Databricks fails during initial setup"""
+
+    def __init__(
+        self,
+        message=None,
+        host_url=None,
+        http_path=None,
+        port=443,
+        user_agent=None,
+        original_exception=None,
+        **kwargs
+    ):
+        # Set up context for connection error telemetry
+        context = kwargs.get("context", {})
+        if host_url:
+            context.update(
+                {
+                    "host_url": host_url,
+                    "http_path": http_path or "",
+                    "port": port,
+                    "user_agent": user_agent,
+                    "original_exception": str(original_exception)
+                    if original_exception
+                    else None,
+                }
+            )
+
+        super().__init__(message=message, context=context, **kwargs)
+
+
+class AuthenticationError(ConnectionError):
+    """Thrown when authentication to Databricks fails"""
+
+    def __init__(self, message=None, auth_type=None, **kwargs):
+        context = kwargs.get("context", {})
+        if auth_type:
+            context["auth_type"] = auth_type
+        kwargs["context"] = context
+
+        super().__init__(message=message, **kwargs)

src/databricks/sql/telemetry/models/event.py

@@ -149,9 +149,9 @@ class TelemetryEvent(JsonSerializableMixin):
         operation_latency_ms (Optional[int]): Operation latency in milliseconds
     """
 
-    session_id: str
     system_configuration: DriverSystemConfiguration
     driver_connection_params: DriverConnectionParameters
+    session_id: Optional[str] = None
     sql_statement_id: Optional[str] = None
     auth_type: Optional[str] = None
     vol_operation: Optional[DriverVolumeOperation] = None

src/databricks/sql/telemetry/telemetry_client.py

@@ -9,14 +9,20 @@
     TelemetryEvent,
     DriverSystemConfiguration,
     DriverErrorInfo,
+    DriverConnectionParameters,
+    HostDetails,
 )
 from databricks.sql.telemetry.models.frontend_logs import (
     TelemetryFrontendLog,
     TelemetryClientContext,
     FrontendLogContext,
     FrontendLogEntry,
 )
-from databricks.sql.telemetry.models.enums import AuthMech, AuthFlow
+from databricks.sql.telemetry.models.enums import (
+    AuthMech,
+    AuthFlow,
+    DatabricksClientType,
+)
 from databricks.sql.auth.authenticators import (
     AccessTokenAuthProvider,
     DatabricksOAuthProvider,
@@ -437,3 +443,76 @@ def close(session_id_hex):
                     logger.debug("Failed to shutdown thread pool executor: %s", e)
                 TelemetryClientFactory._executor = None
                 TelemetryClientFactory._initialized = False
+
+    @staticmethod
+    def send_connection_error_telemetry(
+        error_name: str,
+        error_message: str,
+        host_url: str,
+        http_path: str,
+        port: int = 443,
+        user_agent: Optional[str] = None,
+    ):
+        """Send error telemetry when connection creation fails, without requiring a session"""
+        try:
+            logger.debug("Sending connection error telemetry for host: %s", host_url)
+
+            # Initialize factory if needed (with proper locking)
+            with TelemetryClientFactory._lock:
+                TelemetryClientFactory._initialize()
+
+            # Create driver connection params for the failed connection
+            driver_connection_params = DriverConnectionParameters(
+                http_path=http_path,
+                mode=DatabricksClientType.THRIFT,
+                host_info=HostDetails(host_url=host_url, port=port),
+            )
+
+            error_info = DriverErrorInfo(
+                error_name=error_name, stack_trace=error_message
+            )
+
+            telemetry_frontend_log = TelemetryFrontendLog(
+                frontend_log_event_id=str(uuid.uuid4()),
+                context=FrontendLogContext(
+                    client_context=TelemetryClientContext(
+                        timestamp_millis=int(time.time() * 1000),
+                        user_agent=user_agent or "PyDatabricksSqlConnector",
+                    )
+                ),
+                entry=FrontendLogEntry(
+                    sql_driver_log=TelemetryEvent(
+                        system_configuration=TelemetryHelper.get_driver_system_configuration(),
+                        driver_connection_params=driver_connection_params,
+                        error_info=error_info,
+                    )
+                ),
+            )
+
+            # Send to unauthenticated endpoint since we don't have working auth
+            request = {
+                "uploadTime": int(time.time() * 1000),
+                "items": [],
+                "protoLogs": [telemetry_frontend_log.to_json()],
+            }
+
+            url = f"https://{host_url}/telemetry-unauth"
+            headers = {"Accept": "application/json", "Content-Type": "application/json"}
+
+            # Send synchronously for connection errors since we're probably about to exit
+            response = requests.post(
+                url,
+                data=json.dumps(request),
+                headers=headers,
+                timeout=5,
+            )
+            if response.status_code == 200:
+                logger.debug("Connection error telemetry sent successfully")
+            else:
+                logger.debug(
+                    "Connection error telemetry failed with status: %s",
+                    response.status_code,
+                )
+
+        except Exception as e:
+            logger.debug("Failed to send connection error telemetry: %s", e)