What does the requestedPublishingInterval in milo mean?

Question

In my OPC-UA Client implementation based on milo i need a lot of subscriptions. Therefore i used the example from:

https://github.com/eclipse/milo/blob/master/milo-examples/client-examples/src/main/java/org/eclipse/milo/examples/client/SubscriptionExample.java

But what does the requestedPublishingInterval of 1000.0 in
UaSubscription subscription = client.getSubscriptionManager().createSubscription(1000.0).get();
mean?

Furthermore, where does the parameter _samplingInterval in MonitoringParameters stand for?

Thank you!

Answer 1

The sampling interval is the rate at which you want the server to sample/poll/monitor an item at. Items in a subscription may come from varying sources and each can be sampled at its own rate.

The publishing interval is the rate at which the subscription "executes" and reports any items that have changed. It also influences the calculation that determines how often a keep alive response should be returned should there be no changing data.

OPC UA Specification Part 4 explains all of this in much greater detail.