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Large tag subscription fails to update

Large tag subscription fails to update

Sgilk
Contributor

I have a 1000 tag license for the WebIQ runtime on ctrlX OS. I am able to deploy my 1000 tag project to the runtime, but OPC UA subscription updates are only firing for the first 500 tags.

I am subscribing to the items in a local-script and checking for their updates in a boolean array. As you can see below, indices 0-499 update from the subscription, but 500-999 never update. Any idea what is happening here?

Sgilk_0-1713990694865.png

 

5 REPLIES 5

webiq-sk
Frequent Contributor

Please provide the connect.log from the affected system (optimally in trace mode) so we can look into this. Without the log no analysis is possible.

I solved the problem here after reviewing the connect.log. 

[     warning |      io_extension_item]   error_code(): opcua:-2133131264:BadTooManyMonitoredItems

On the OPC UA server side, there was a limit of 500 monitored items per subscription.

There is one other piece of strange behavior. I am seeing that subscribed items often update multiple times before the entire set of items updates once. For example, if I have an array of 1000 items, item 1 may update twice before item 1000 updates once. There is nothing in the trace logs that indicates a related problem.

webiq-sk
Frequent Contributor

You can create a Wireshark log (when not using OPC-UA encryption) and investigate if your OPC UA server is the reason or WebIQ server. Please note that in OPC UA the OPC-UA server always sends updates as it's not a pull meachanism, but a subscription mechanism where the server sends the data to the client.

Is this possible when the OPC UA server and WebIQ server are both running on the ctrlX CORE? The wireshark traffic I see to my PC WebIQ client is all TCP and TLS.

webiq-sk
Frequent Contributor

Probably not, then simply switch to unencrypted traffic and use WebIQ on a local system on the network - then you should be able to diagnose this.

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