OP5 Monitor - How to fix "Undefined property: CorePDOHandler" in Nagvis

This error is likely caused by an incorrect back-end being set either globally or for a specific map.

Try the following command:

# cd /opt/monitor/op5/nagvis_ls/etc && grep -rni "backend="

This output should tell you whether the default setting (nagvis.ini.php) or a map-specific setting has changed to one that doesn't work, which will throw the error shown below. In almost all cases, expect this setting to be the default, which is:

backend="live_1"

Change this value either in the default setting file (nagvis.ini.php) or in the specific map file containing another value and the error should disappear. There is no need to restart Apache.

An alternate solution is to move the problematic map file out of the way which stops the error from appearing, or with an incorrect general setting, move all map files away so the value can be changed in the GUI before moving them back.

Error shown in GUI (example)

Error: (0) Undefined property: CorePDOHandler::$data
URL: /nagvis/server/core/ajax_handler.php?mod=Overview&act=getObjectStates&i[]=map-weather_test&_ajaxid=1589535949
File: /opt/monitor/op5/nagvis_ls/share/server/core/classes/CorePDOHandler.php
Line: 306
#0 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CorePDOHandler.php(306): nagvisExceptionErrorHandler(8, 'Undefined prope...', '/opt/monitor/op...', 306, Array)
#1 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CorePDOHandler.php(332): CorePDOHandler->prep('SELECT? ...')
#2 /opt/monitor/op5/nagvis_ls/share/server/core/classes/GlobalBackendPDO.php(485): CorePDOHandler->query('SELECT? ...', Array)
#3 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CoreBackendMgmt.php(478): GlobalBackendPDO->getHostState(Array, 0, Array)
#4 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CoreBackendMgmt.php(169): CoreBackendMgmt->fetchStateCounts('ndomy_1', 'hostState', 0, Array)
#5 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CoreModOverview.php(171): CoreBackendMgmt->execute()
#6 /opt/monitor/op5/nagvis_ls/share/server/core/classes/CoreModOverview.php(64): CoreModOverview->parseMapsJson(false, Array)
#7 /opt/monitor/op5/nagvis_ls/share/server/core/functions/index.php(120): CoreModOverview->handleAction()
#8 /opt/monitor/op5/nagvis_ls/share/server/core/ajax_handler.php(59): require('/opt/monitor/op...')
#9 {main}