Hello
We are currently subscribing to 250+ nodes. Each node has it's own sub nodes with data we require. The client wants to receive data every 100ms and update the elements on screen.
Is this too much for the opc ua? What is the maximum amount? (publishing interval for datachanged is set to 100ms)
There is data that is skipped entirely when publishing.
With kind regards,
Mehmed
Maximum amount of nodes?
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Support Team
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Re: Maximum amount of nodes?
Hello,
the speed/frequency of sending updates is fully controlled by the data source (the UA server). All known OPC UA servers protect themselves by providing (moderate) update speed for the nodes they monitor. If your client connects to a server you can only "request" high frequency updates, however the server will "revise" the real scan- and publish- rate he is willing to do. This is a protection mechanizm to not force the UA server into a 100% CPU load scenario. Secondly, the server implementation has strong influence on the speed/frequency, if the server is just a gateway to a serial bus with 9800 bd transmission, the 250+ tags may become challenging. Third, the data will be published only if it has value-change, if not changed the data is not published. You must make sure that the data is changing "faster than" the scan- and the publish rate to ensure a value change is detected.
However, typically the 250 nodes seem not being much (not sure what you mean by "subnodes", this term does not exist in OPC UA). A PC based OPC UA Server should be able to (easily) provide 40,000+ nodes (of type UInt32) within 100ms (assuming in-memory nodes, but not mapped nodes from a slow underlying serial bus). All your 40000 values must change within (faster than) 100ms.
There is no way to loose data in OPC UA, the scan rate on the data source can be much faster than the publish rate over the wire (OPC UA has data queue, must be supported by the server). The publish rate is always to be seen as "not faster than", rather than guaranteed speed.
the speed/frequency of sending updates is fully controlled by the data source (the UA server). All known OPC UA servers protect themselves by providing (moderate) update speed for the nodes they monitor. If your client connects to a server you can only "request" high frequency updates, however the server will "revise" the real scan- and publish- rate he is willing to do. This is a protection mechanizm to not force the UA server into a 100% CPU load scenario. Secondly, the server implementation has strong influence on the speed/frequency, if the server is just a gateway to a serial bus with 9800 bd transmission, the 250+ tags may become challenging. Third, the data will be published only if it has value-change, if not changed the data is not published. You must make sure that the data is changing "faster than" the scan- and the publish rate to ensure a value change is detected.
However, typically the 250 nodes seem not being much (not sure what you mean by "subnodes", this term does not exist in OPC UA). A PC based OPC UA Server should be able to (easily) provide 40,000+ nodes (of type UInt32) within 100ms (assuming in-memory nodes, but not mapped nodes from a slow underlying serial bus). All your 40000 values must change within (faster than) 100ms.
There is no way to loose data in OPC UA, the scan rate on the data source can be much faster than the publish rate over the wire (OPC UA has data queue, must be supported by the server). The publish rate is always to be seen as "not faster than", rather than guaranteed speed.
Best regards
Unified Automation Support Team
Unified Automation Support Team
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m.kumali
- Full Member
- Posts: 5
- Joined: 20 Oct 2020, 12:55
Re: Maximum amount of nodes?
Hello again,
Thank you for your reply. By sub nodes I meant the child nodes of the one we have subscribed to. I am monitoring the data via Ua expert as well and it's being updated correctly, however our client seems to sometimes skip some of the updates. I cannot quite find the issue since you said the limit should be well over 40,000. The only way I have managed to fix this is by lowering the amount of subscribed nodes.
With kind regards,
Mehmed
Thank you for your reply. By sub nodes I meant the child nodes of the one we have subscribed to. I am monitoring the data via Ua expert as well and it's being updated correctly, however our client seems to sometimes skip some of the updates. I cannot quite find the issue since you said the limit should be well over 40,000. The only way I have managed to fix this is by lowering the amount of subscribed nodes.
With kind regards,
Mehmed