Building OPC UA Server for Historical Data Access using eclipse milo

问题

I’m new to OPC-UA and came across eclipse milo project. Project seems interesting but there is very little developer help. I am trying to browse code to figure out how to implement Node with historical data. Project has other examples for reference but missing history service example. I tried to modify provided example in ExampleNameSpace.java to enable history on the UaVariableNode but in Prosys OPC UA Client, it doesn't enable "Show History" menu for the Node. Here is what I tried

UaVariableNode node = new UaVariableNode.UaVariableNodeBuilder(server.getNodeMap())
            .setNodeId(new NodeId(namespaceIndex, "HelloWorld/Dynamic/" + name))
            .setAccessLevel(ubyte(AccessLevel.getMask(AccessLevel.READ_WRITE)))
            .setBrowseName(new QualifiedName(namespaceIndex, name))
            .setDisplayName(LocalizedText.english(name))
            .setDataType(typeId)
            .setTypeDefinition(Identifiers.BaseDataVariableType)
            **.setHistorizing(true)**
            .build();

It will be very helpful if some one who implemented historyService using milo can share example.

UPDATE: Sorry, I should have included other part that I implemented. After reading other stack overflow post, I implemented historyRead function in namespace, which will take care of pulling history reading from datastore. My trouble right now is to indicate OPC client that Node is history capable. Test is to make prosys OPC client to enable "History" menu for the Node. I am probably missing something here.

回答1:

The Milo Server SDK does not implement historical services for you.

Setting the Historizing attribute is just the tip of the iceberg. Your Namespace also has to override the historyRead (and historyUpdate if you want to support it) methods defined in AttributeHistoryManager and provide implementations. This will be impossible if you're not familiar with how UA history works, which is all defined in Part 11 of the spec.

You'll also have to take responsibility for actually storing the history for any nodes that have their Historizing attribute set, so that the services you implement actually have some data to go and query.

FWIW, developer documentation is a work in progress and should drastically improve in the next couple releases.

History is unlikely to ever be implemented as part of the SDK in such a way that you can just flip a switch and it will start working. It's fairly complicated and an efficient implementation of the services is likely to be coupled to whatever backing store you're using.

来源：https://stackoverflow.com/questions/47556432/building-opc-ua-server-for-historical-data-access-using-eclipse-milo

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