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Publish (onDataChange) comes twice after short network failure

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Publish (onDataChange) comes twice after short network failure

May 5, 2022
11:25, EEST

rocket science

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March 16, 2017

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Hi,

I had an issue after a short network failure which seems to result in the onDataChanges coming twice for a subscription. (SDK Version is 4.3.0)

So what I could see in the logs is that it seems the connection to the Opc Server (KepServer EX) was lost

~ 5 seconds later the connection was back again. According to the logs, it seems that the session was reactivated.

2022-05-03 09:47:22,729|UaClient |INFO |reconnect: Reconnected to server (session reactivated)

After the reconnect I’m always getting the onDataChanges twice per change for the monitored item which is in the subscription

2022-05-03 09:50:43,433|MySubscription |INFO |onDataChange(new value is [DataValue(value=5985, statusCode=GOOD (0x00000000) "", sourceTimestamp=05/03/22 13:50:43.3237153 GMT, sourcePicoseconds=0, serverTimestamp=05/03/22 13:50:43.3237153 GMT, serverPicoseconds=0)], old value was [DataValue(value=5984, statusCode=GOOD (0x00000000) "", sourceTimestamp=05/03/22 13:46:55.2981594 GMT, sourcePicoseconds=0, serverTimestamp=05/03/22 13:46:55.2981594 GMT, serverPicoseconds=0)]
2022-05-03 09:50:43,433|MySubscription |INFO |onDataChange(new value is [DataValue(value=5985, statusCode=GOOD (0x00000000) "", sourceTimestamp=05/03/22 13:50:43.3237153 GMT, sourcePicoseconds=0, serverTimestamp=05/03/22 13:50:43.3237153 GMT, serverPicoseconds=0)], old value was [DataValue(value=5984, statusCode=GOOD (0x00000000) "", sourceTimestamp=05/03/22 13:46:55.2981594 GMT, sourcePicoseconds=0, serverTimestamp=05/03/22 13:46:55.2981594 GMT, serverPicoseconds=0)]

I get this onDataChanges twice as long as the client application was running. After restarting the client application anb subscribing to the data item ‘from scratch’ everthing was back to normal so I got the onDataChange only once per change.

I wonder if this might be a problem in the client SDK when a session is reactivated, or it might be a problem of the KepServer EX ?

Any thoughts on this?

May 5, 2022
14:19, EEST

Matti Siponen

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February 11, 2020

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Hello,

Would you be able replicate this error and use Wireshark to capture communication between the Client and KepServer EX starting from when MonitoredItems are created for the first time to the Client receiving duplicate DataChangeNotifications after reconnecting? You can send the capture log to uajava-support@prosysopc.com for analysis.

Alternatively, you can set your Client’s logging level to debug to see whenever MonitoredItems are added to a Subscription. The log entries should look like “addItem: [item]”, where [item] is an instance of MonitoredItemBase class. If the Client is creating duplicates of MonitoredItems after reconnecting, there could be an error in the SDK.

May 5, 2022
16:25, EEST

rocket science

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March 16, 2017

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Hi,

unfortunatly I’ve not been able yet to reproduce it, but if I’ve found a way I will provide a Wireshark capture.

Thank you!

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