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dcntrd
Apr 2, 2026

I'm creating a subscription with a monitored item:

OpcUaSubscription uaSubscription = new OpcUaSubscription(uaClient);
uaSubscription.setPublishingInterval(...);
uaSubscription.setLifetimeCount(...);
uaSubscription.setMaxKeepAliveCount(...);
uaSubscription.setMaxNotificationsPerPublish(...);
uaSubscription.setPriority(...);
uaSubscription.setSubscriptionListener(new Listener());

uaSubscription.create();

uaSubscription.setPublishingMode(publishingEnabled);

Then I'm adding a monitored item:

ReadValueId readValueId = new ReadValueId(nodeId, AttributeId.Value.uid(), indexRange, QualifiedName.NULL_VALUE);
OpcUaMonitoredItem monitoredDataItem = new OpcUaMonitoredItem(readValueId, monitoringMode);
monitoredDataItem.setDataValueListener(new ValueConsumer(...));
monitoredDataItem.setQueueSize(queueSize);
monitoredDataItem.setSamplingInterval(samplingInterval);

uaSubscription.addMonitoredItem(monitoredDataItem);

And finally call synchronizeMonitoredItems and log the OpcUaSubscription

subscription.synchronizeMonitoredItems();
LOG.debug("synchronizeMonitoredItems for subscription: " + subscription);

The logging shows:

...synchronizeMonitoredItems for subscription: OpcUaSubscription[subscriptionId=1775131576, syncState=UNSYNCHRONIZED]

I would have expected that the syncState=SYNCHRONIZED.

Am I'm doing something wrong?

The subscription itself seems to work and I'm getting data changes.
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Replies: 2 comments · 4 replies

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kevinherron
Apr 2, 2026
Maintainer

Hmm, that seems like a reasonable expectation. I wonder if the syncState isn't being updated after synchronizeMonitoredItems() or any of the other item modification methods run.

I'll look into it. Seems like it could be a bug.
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2 replies
@kevinherron
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kevinherron Apr 2, 2026
Maintainer

Yeah, it looks like originally OpcUaSubscription.SyncState was about tracking creation of and modifications to the Subscription settings, not including adding/removing MonitoredItems, then at some point grew to include MonitoredItem add/remove, but the logic isn't complete.
@dcntrd
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dcntrd Apr 2, 2026
Author

Yes, I can confirm that the syncState = SYNCHRONIZED after

uaSubscription.create();

after

uaSubscription.addMonitoredItem(monitoredDataItem);

it is UNSYNCHRONIZED

and after

subscription.synchronizeMonitoredItems();

it stays UNSYCHRONIZED
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kevinherron
Apr 2, 2026
Maintainer

Okay, so what I'm leaning towards is: fully decouple OpcUaSubscription.SyncState from monitored items, like I think was the original intention. There's already a OpcUaMonitoredItem.SyncState for each item.

This means OpcUaSubscription.SyncState is only about Subscription creation and settings sync; adding and removing items would not change this state.

Then add isFullySynchronized() and possibly getAggregateSyncState() that would allow you to get the combined state of subscription + item synchronization. AggregateSyncState would be a new enum or something. Might be enough to just have the boolean isFullySynchronized() that was something like:

public boolean isFullySynchronized() {
    return syncState == SyncState.SYNCHRONIZED
        && monitoredItems.values().stream()
               .allMatch(item -> item.getSyncState() == OpcUaMonitoredItem.SyncState.SYNCHRONIZED);
}
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2 replies
@dcntrd
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dcntrd Apr 4, 2026
Author

Sounds good
@kevinherron
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kevinherron Apr 4, 2026
Maintainer

#1726
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