Server requirements
Depending on the features used, the OPC UA extractor places certain requirements on the server. If these aren't fulfilled, the feature won't work, and the extractor may crash.
Base
These services are required for all servers the OPC UA extractor connects to:
- Session management - The server must support connections from clients and be able to manage at least one session.
- Browse and BrowseNext - These services are used for mapping the node hierarchy and must be supported. If the server doesn't support BrowseNext, it must return all child nodes on a single request. It's possible to get around this limitation by adjusting the
browse-chunk
andbrowse-nodes-chunk
configuration parameters. - Read - The server must support the Read service to read attributes for nodes.
Variables
Any server that has data variables to read from must support these:
- Create Subscription - The client must be able to create new subscriptions.
- Create Monitored Item - The client must be able to create new monitored items on an existing subscription.
- Publish - The server must handle publish requests from the client in a good way.
- Notifications on data changes - The server must provide clean notifications on data changes to the client.
History
To read from a server with History set to true
, the server must support the following:
- HistoryReadRaw - Data is only read using the ReadRaw mode history read. The server must support this.
- ContinuationPoints - The server must return a
continuationPoint
if a single request is insufficient to fetch all data points for a given node. - Historizing - Any variable that supports history must have its Historizing attribute set to
true
.
Backfill
To backfill, the server must support the following:
- History read ordering - If start/endtime is reversed in a
historyRead
call, the data must be returned in reverse order. If not, backfill may not work properly.