Retry keep alive disconnects (#48)

CHANGELOG.md

@@ -4,6 +4,17 @@
 
 * In the next minor release (0.3.0) the row_binary option for ClickHouse serialization will be removed.  The performance is significantly lower than Native format and maintaining the option adds complexity with no corresponding benefit
 
+### Release 0.2.10 2022-09-28
+
+#### Bug Fix
+* Add single retry for HTTP RemoteDisconnected errors from the ClickHouse Server.  This prevents exception spam when requests (in particular inserts) are sent at approximately the same time as the ClickHouse server closes a keep alive connection.
+
+### Release 0.2.9 2022-09-24
+
+#### Bug Fix
+* Fix incorrect validation errors in the Superset connection dialog
+
+
 ### Release 0.2.8 2022-09-21
 
 #### Improvements

clickhouse_connect/VERSION

@@ -1 +1 @@
-0.2.9
+0.2.10

clickhouse_connect/driver/client.py

@@ -94,7 +94,7 @@ def query(self,
               use_none: bool = True,
               context: QueryContext = None) -> QueryResult:
         """
-        Main query method for SELECT, DESCRIBE and other commands that result a result matrix
+        Main query method for SELECT, DESCRIBE and other SQL statements that return a result matrix
         :param query: Query statement/format string
         :param parameters: Optional dictionary used to format the query
         :param settings: Optional dictionary of ClickHouse settings (key/string values)

clickhouse_connect/driver/httpclient.py

@@ -3,6 +3,7 @@
 import atexit
 import re
 import http as PyHttp
+from http.client import RemoteDisconnected
 
 from typing import Optional, Dict, Any, Sequence, Union, List
 from requests import Session, Response, get as req_get
@@ -265,6 +266,17 @@ def _raw_request(self,
                                                           data=data,
                                                           params=params)
             except RequestException as ex:
+                rex_context = ex.__context__
+                if rex_context and isinstance(rex_context.__context__, RemoteDisconnected):
+                    # See https://github.com/psf/requests/issues/4664
+                    # The server closed the connection and it is probably because the Keep Alive has expired
+                    # We should be safe to retry, as ClickHouse should not have processed anything on a connection
+                    # that it killed.  We also only retry this once, as multiple disconnects are unlikely to be
+                    # related to the Keep Alive settings
+                    if attempts == 1:
+                        logger.debug('Retrying remotely closed connection')
+                        attempts = 0
+                        continue
                 logger.exception('Unexpected Http Driver Exception')
                 raise OperationalError(f'Error executing HTTP request {self.url}') from ex
             if 200 <= response.status_code < 300: