Event Monitor Item
An item used to subscribe to events from the OPC UA server.
The Event Monitor Item has the following properties:
| Name | Description | ID | Flags |
|---|---|---|---|
| SrcUaNodeId | The UA Node ID in the source server which should be monitored for events. | 5031 | Persisted |
| EventType NodeId | The UA Node ID of the base EventType this monitor should subscribe to. | 13000 | Persisted |
| UnmappedEventsourceAction | The action to perform when a received event has an unknown eventsource | 13001 | Persisted |
| LookupSourcePathTemplate | Template string used to construct an eventsource path from the received event fields | 13002 | Persisted |
| UnmappedEventtypeAction | The action to perform when a received event has an unknown eventtype | 13003 | Persisted |
| CatchupPeriod | Maximum number of seconds with event history to catchup after being disconnected | 13110 | Persisted |
The property UnmappedEventsourceAction can have one of the following values, which decide the action to take when an event with unknown eventsource nodeid is received:
- DropEvent: the event is dropped
- UseModuleAsEventsource: the module containing the Event Monitor Item is used as the eventsource
- LookupSourcename: the sourcename field of the event is used to lookup a fully qualified itemname in Apis Hive. If such an item is found, it will be used as the event source, automatically creating the needed source in Apis Event Server if required.
- LookupSourcepath: A sourcepath is created from the property LookupSourcePathTemplate, and if exactly one event source in Apis Event Server matches the path, this is used as the event source.
The property LookupSourcePathTemplate is a string with injected event field values. Any event field can be referenced in the template with the syntax $(BrowseName), e.g. "Server/Plant/*/ABC-$(SourceName)". The search is case-insensitive and supports the following operators:
- *: matches zero or more characters
- ?: matches one character
- #: matches one digit
- []: match any character between the '[' and ']', unless the first character after '[' is '^', in which case the logic is inverted.
The property UnmappedEventtypeAction can have one of the following values, which decide the action to take when an event with unknown eventtype is received:
- DropEvent: the event is dropped
- UseParentType: traverse the OPC UA eventtype hierarchy and use the first known parent-type
The property CatchupPeriod, with a value greater than 0, causes the Event Monitor Item to perform history-read requests for periods where the OpcUa-module has been disconnected. This happens simultaneously with subscribing for realtime events.