Hello, I'm new to this mailing list, so excuse if this is not the right place to ask for help. We use Zope2 as Web server for our Web User Interface to our Enteprise Job Scheduling System (schedulix/BICsuite). Everything went fine for years now. But now we encounter a nasty error at a customer site (see Errorlog at end of this post). The error occures at different sorce code locations but always when accessing context.REQUES['SESSION']. It is not reproducible on every call but seems to be related to some race condition. I worked around the problem by catching the SystemError and raising a ConflictError to retry the transaction. Retrying just the SESSION access will not resolve the error (tested). This solution is ugly and just hides the symptom of the problem. I would prefer a solid solution of the cause of the problem. Information on Python and Zope Versions can be found in the error log below. Can anyone help me to find a solution to this problem ? Regards Dieter Errorlog: ------------------------------------------------------------------------------------------------------- Site Error Log Site Error Log at /error_log Exception traceback Time 2018/03/27 18:24:16.825451 GMT-7 User Name (User Id) omaryr (omaryr) Request URL http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorDisplayPage Exception Type SystemError Exception Value error return without exception set Traceback (innermost last): Module ZPublisher.Publish, line 138, in publish Module ZPublisher.mapply, line 77, in mapply Module ZPublisher.Publish, line 48, in call_object Module Shared.DC.Scripts.Bindings, line 322, in __call__ Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec Module Products.PythonScripts.PythonScript, line 344, in _exec Module script, line 1, in NavigatorDisplayPage <PythonScript at /SDMS/NavigatorDisplayPage used for /SDMS/SDMSDesigner/Group> Line 1 Module Shared.DC.Scripts.Bindings, line 322, in __call__ Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec Module Products.PythonScripts.PythonScript, line 344, in _exec Module script, line 521, in DefaultNavigatorDisplay <PythonScript at /SDMS/Common/Pages/DefaultNavigatorDisplay> Line 521 Module AccessControl.ZopeGuards, line 83, in guarded_getitem Module ZPublisher.HTTPRequest, line 1371, in __getitem__ Module ZPublisher.HTTPRequest, line 1337, in get Module Products.Sessions.SessionDataManager, line 101, in getSessionData Module Products.Sessions.SessionDataManager, line 188, in _getSessionDataObject Module Products.Transience.Transience, line 839, in new_or_existing Module Products.Transience.Transience, line 495, in get Module Products.Transience.Transience, line 285, in _move_item Module Products.Transience.Transience, line 934, in _housekeep Module Products.Transience.Transience, line 574, in _finalize Module Products.Transience.Transience, line 598, in _do_finalize_work SystemError: error return without exception set Display traceback as text REQUEST form SDMS_CONNECTION 'ADMIN' cookies _ZopeId '58327093A8Z3xR9JT8w' lazy items SESSION <bound method SessionDataManager.getSessionData of <SessionDataManager at /session_data_manager>> other SUBMIT_DONE 0 NEW_EXPAND_STATE [] REQUEST_INITIALIZED True PUBLISHED <PythonScript at /SDMS/NavigatorDisplayPage used for /SDMS/SDMSDesigner/Group> NAV_MODE 'NAVIGATE' SDMS_Version 'PROFESSIONAL' SDMS_Server {'CACHE': 'Y', 'SSL': 'N', 'HOST': 'localhost', 'VERSION': 'PROFESSIONAL', 'TIMEOUT': '60', 'PORT': '2506'} SDMS_Host 'localhost' SCROLL_X '0' SCROLL_Y '0' AUTHENTICATION_PATH '' EXPAND_STATE '[]' LANG 'EN' PINNED_PATH '[]' USERCONFIGCACHE {'LANG': 'EN', 'Connections': "[{'NAME': 'ADMIN', 'DEFAULT': 'true', 'SERVER': 'DEFAULT', 'ENVIRONMENT': 'NONE', 'USER': 'OMARYR', 'SERVER_DEFAULT': 'false'}, {'NAME': 'BATCH_OPERATOR', 'DEFAULT': 'false', 'SERVER': 'DEFAULT', 'ENVIRONMENT': 'NONE', 'USER': 'OMARYR_BATCH_OPERATOR', 'SERVER_DEFAULT': 'false'}]", 'UserDefaultFontSize': '13', 'LookAndFeelFolder': 'LookAndFeelGrey', 'UserDefaultFontFamily': 'Arial,Helvetica', 'REFRESH_SECS': '300'} SDMS_Password '<password obscured>' FIND_PATTERN '' AUTHENTICATED_USER <User 'omaryr'> DISPLAY_LEAFS 'N' BICWEB_RETRY 0 SERVER_URL 'http://localhost:8080' traverse_subpath [] SHOW_LOCKED 'N' SHOW_FOLDERPATH 'N' method 'GET' F_CHANGED 'N' OLD_EXPAND_STATE [] PINNED_ID_LIST [] F_MODE 'UNKNOWN' URL 'http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorDisplayPage' F_RETURN 'N' SDMS_User 'OMARYR' SDMSROOT '/' PINNED_PATH_LIST [] LOOK_AND_FEEL <Folder at /SDMS/Common/LookAndFeelGrey> SDMS_Port '2506' SDMS_CONNECTION 'ADMIN' SET_CONNECT_DATA True PINNED_IDS '[]' TraversalRequestNameStack [] SDMS_ServerName 'DEFAULT' AUTO_REFRESH 'false' SUBMIT 'INIT' F_READONLY 'N' SHOW_HIERARCHYPATH 'N' SHOW_DEPENDENCIES 'Y' ACTUAL_URL 'http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorDisplayPage' REFRESH_SECS '300' URL0 http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorDisplayPage URL1 http://localhost:8080/SDMS/SDMSDesigner/Group URL2 http://localhost:8080/SDMS/SDMSDesigner URL3 http://localhost:8080/SDMS URL4 http://localhost:8080 BASE0 http://localhost:8080 BASE1 http://localhost:8080 BASE2 http://localhost:8080/SDMS BASE3 http://localhost:8080/SDMS/SDMSDesigner BASE4 http://localhost:8080/SDMS/SDMSDesigner/Group BASE5 http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorDisplayPage environ HTTP_COOKIE '_ZopeId="58327093A8Z3xR9JT8w"' SERVER_SOFTWARE 'Zope/(2.13.26, python 2.7.5, linux2) ZServer/1.1' SCRIPT_NAME '' REQUEST_METHOD 'GET' PATH_INFO '/SDMS/SDMSDesigner/Group/NavigatorDisplayPage' SERVER_PROTOCOL 'HTTP/1.1' QUERY_STRING 'SDMS_CONNECTION=ADMIN' channel.creation_time 1522200256 CONNECTION_TYPE 'keep-alive' HTTP_USER_AGENT 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36' HTTP_REFERER 'http://localhost:8080/SDMS/SDMSDesigner/Group/NavigatorPage?SDMS_CONNECTION=...' SERVER_NAME 'localhost' REMOTE_ADDR '192.168.5.39' PATH_TRANSLATED '/SDMS/SDMSDesigner/Group/NavigatorDisplayPage' SERVER_PORT '8080' HTTP_HOST 'localhost:8080' HTTP_UPGRADE_INSECURE_REQUESTS '1' HTTP_ACCEPT 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8' GATEWAY_INTERFACE 'CGI/1.1' HTTP_ACCEPT_LANGUAGE 'en-US,en;q=0.9' HTTP_ACCEPT_ENCODING 'gzip, deflate' -- independIT Integrative Technologies GmbH Bergstrasse 6 86529 Schrobenhausen HRB Ingolstadt 101.521 Geschäftsführer: Dieter Stubler, Dipl. Inform. (FH) Ronald Jeninga, Diplom Mathematiker e-mail: dieter.stubler@independit.de web: http://www.independit.de Tel: +49 8252 9658033 GSM: +49 172 7052833 Fax: +49 8252 9658034