Subscription behavior

[slore]

Hello guys,

I am fairly new to opc-ua and I am trying to build an HMI that communicates via opc-ua to the PLC.

In order to update the visualization, after any change in the PLC monitored tags, I am exploiting the subscription strategy instead of polling.

I am seeing a strange behavior in the subscription response time: after a change in the PLC tag it takes even up to 3sec to trigger the event reaction. I have made the same test with UA expert and it's almost instantaneous.
To be honest this response time can vary much: from some millisec to many seconds.

to be more accurate: I am subscriving to 2000 plc tags.

Could you please guide me to correct this behavior?

[AndreasHeine]

what publishinterval did you use?

[AndreasHeine]

how many subs do you have?

1 Sub with 2k MonitoredItems
or
2k Subs with 1 MonitoredItem

[AndreasHeine]

typically the first is recommended (1 Sub with 2k MonitoredItems)

[slore]

Here could be the issue: I have 2kSubs with 1MonitoredItem.

How can I do the other way around?

Thanks!!

[AndreasHeine]

first of all some background: https://reference.opcfoundation.org/v104/Core/docs/Part4/5.13.1/
create one sub and with that sub call await sub.subscribe_data_change(nodelist) (nodelist = [...2k nodes....]) and inside the SubHandler you can make sorting to a python variable (according to the node-id) or putting it just in a queue in order to process it in a different task or subprocess (the important thing is do not do blocking stuff in the SubHandler the handler method will be called for each datachange notification in the subscriptions publishresponse)

[slore]

I want to thank you, I defenitelly solved my issue with your help.