Subscribing to complex datatypes

[MSasurinen]

Currently, the OPC publisher IoT edge module is a great tool for simple data like a sensor value here and there. But if you try to subscribe to a complex data type such as a custom struct, the messages coming from the module are a mixture of json and uadb (or plain uadb depending on the cmd-line arguments). An example of such a message, containing two nodes, one bool, and one custom struct:

[
  {
    "NodeId": "urn:BeckhoffAutomation:Ua:PLC1#s=.gstSecLoadings.arstSecLd%5b1%5d.bLoadingReady",
    "ApplicationUri": "urn:BeckhoffAutomation:TcOpcUaServer",
    "DisplayName": "LoadingReady",
    "Value": {
      "Value": false,
      "SourceTimestamp": "2021-08-25T05:27:25.549262Z"
    }
  },
  {
    "NodeId": "urn:BeckhoffAutomation:Ua:PLC1#s=arrstTest%5b1%5d",
    "ApplicationUri": "urn:BeckhoffAutomation:TcOpcUaServer",
    "DisplayName": "arrstTest",
    "Value": {
      "Value": {
        "TypeId": "urn:BeckhoffAutomation:Ua:PLC1#s=%3cStructuredDataType%3e%3arrstTest_DefaultBinary",
        "Body": "BgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAe0VIFJjXASwAAABUaW1lb3V0IHdoZW4gd2FpdGluZyBjb25maWd1cmF0aW9uIGZyb20gQ09OTgAAAAACAAAAAQAAAACRAAA="
      },
      "SourceTimestamp": "2021-08-25T05:27:25.549262Z"
    }
  }
]

I am using version 2.7 in a standalone configuration. And the cmdl arguments go as follows:

  "Hostname": "OPCPublisher",
  "Cmd": [
    "--pf=/mount/pn.json",
    "--bs=2",
    "--aa",
    "--mm PubSub",
    "--me=Json"

Is there a way to decode the body of the second node in the cloud or in another iot edge module?
If not, could this be a feature? I'm thinking something on the lines of adding the reading of the DatatypeDictionary from the server at startup, which would bring the information of the DataTypes to the Publisher, and then while configuring the nodes the developer could set the type of the node in the pn.json file.

To reproduce the example message above:

• Define the message encoding to json via the command-line arguments for the module
• Create a struct-type variable at a PLC
• Publish it at an OPC ua Server
• Subscribe to it
• Cause a change on it

Hope this is the right way to ask/suggest this kind of thing.
Br,
Markus

[koepalex]

@Mkasakka which version of OPC Publisher are you using? Do you use it standalone (which I expect) or as part of Industrial IoT Platform?

Please try to use --mm PubSub and also paste the output

[MSasurinen]

Hi, yes you are correct I am using the Publisher in standalone mode. The current version is 2.7 and the output in the initial post is now with the message mode "PubSub".

[koepalex]

I've tested the OPC Publisher in standalone version 2.8.0 with the complexe data type of iot-edge-opc-plc (with --ctb) and the complexe data type is working:

{
      "MessageId": "379",
      "MessageType": "ua-data",
      "PublisherId": "opc.tcp://localhost:50000_39d40f4aae5f07696bc0737f6ba45a4d4bd63d79",
      "DataSetWriterGroup": "opc.tcp://localhost:50000_39d40f4aae5f07696bc0737f6ba45a4d4bd63d79",
      "Messages": [
        {
          "DataSetWriterId": "opc.tcp://localhost:50000_ad96df769e92a48dd17e03373f81ee07296dbfc4",
          "MetaDataVersion": {
            "MajorVersion": 1,
            "MinorVersion": 0
          },
          "Payload": {
            "http://microsoft.com/Opc/OpcPlc/Boiler#i=15013": {
              "Value": {
                "Temperature": {
                  "Top": 3360,
                  "Bottom": 3365
                },
                "Pressure": 103365,
                "HeaterState": "On_1"
              },
              "SourceTimestamp": "2021-08-25T09:14:05.416079Z"
            }
          }
        }
      ]
    }

So it could be that the OPC UA stack (complexe data type) can't decode your custom type. Would it be possible that you provide an public available endpoint of the OPC UA server, that we can connect and check the data type definitions?

[MSasurinen]

Hi, sadly I can not provide access to the server. Maybe these help? The first is the description of the node that I try to subscribe to (the above output is was for a test node, the same problem though). And the second one is the definition of ST_Mess_Latest. If there is a problem with encoding custom data types, how would one address it?

[koepalex]

@mregen is this information sufficient or do we require something else?

[mregen]

Hi @Mkasakka, what you get in the Body of the JSON message is the binary encoding of the structure.
Looks like the complex type decoder cannot specifically handle this Array of structures in a structure of complex type.
Please help by getting me the description of the DataTypeDefinition from the server for the missing type.
As a sample here is the BoilerType we used above:

Find the DataType in Types/DataTypes/Structure, e.g. like here:

then if possible, expand all fields of the DataTypeDefinition:

and copy the content. Then we can try to repro the case here and see why we cannot decode it.

[MSasurinen]

Hi, sure thing!
Here is the structure of which the array is composed.

[mregen]

Hi @Mkasakka , based on the screenshot I cannot root cause the issue. By any chance, could you provide the Nodeset2 or other model files? Is this a custom model or companion spec?
As its a nested data structure its hard to tell for me where the code fails here.

[MSasurinen]

Sure anything you need! As I understand it is a custom model, can you elaborate on what file you need?

[mregen]

Hi @Mkasakka , there might be files with extension *.nodeset2.xml in your plc project. Some are used for companion specs and are included by others, very likely there are some files which describe e.g. ST_MESSAGE_INFO.

[MSasurinen]

Hi, sorry to say this but I do not find any files with that suffix. Could it have something to do with the fact that I am using the Opc ua server from Beckhoff?

[hansgschossmann]

Hi @Mkasakka the *.nodeset2.xml file does describe the OPC UA namespace of the server. I am not familiar with the Beckhoff modeling tool. Can you check with the Beckhoff documentation (or the people who have configured the OPC UA servers address space) what would be the equivilant to the nodeset2.xml file?

[marcschier]

Close stale issue