No events from a TwinCAT server

[danmoser]

Hi! I've been working good with event subscriptions in a number of servers using the code below:

myHandler = SubHandler()
clientSubs = await client.create_subscription(0, myHandler)
# ...
evLogNS = client.get_node(ua.NodeId("EventLogger", 8))
evSubs = await clientSubs.subscribe_events(evLogNS)
# ...
sm_statusNS = client.get_node("ns=8;s=NodeString")
sm_monitor = await clientSubs.subscribe_data_change(sm_statusNS)

However, connecting to a TwinCAT (Beckhoff) server, and I'm not getting any event notifications. Data change notifications are working fine (I've doubled checked the EventLogger nodeId, and it's correct.) UaExpert is receiving the Events from this server+nodeId as expected.

Any ideas on how to debug this?

[AndreasHeine]

hey @danmoser unfortunatly i dont have Beckhoff hardware to test against!
what EventType/'s does the EventLogger emit?

[schroeder-]

You could try to set a custom eventfilter, to rule out a error in the eventfilter generation.
This is a example for an eventfilter for an AlarmConditionType:

            content_filter = ContentFilter(
            [
                ContentFilterElement(
                    FilterOperator.OfType,
                    [LiteralOperand(Variant(NodeId(ObjectIds.AlarmConditionType)))],
                )
            ]
        )
        filt = EventFilter(
            [
                SimpleAttributeOperand(
                    BrowsePath=[QualifiedName("EventType")],
                    AttributeId=AttributeIds.Value,
                    TypeDefinitionId=NodeId(ObjectIds.BaseEventType),
                ),
                SimpleAttributeOperand(
                    BrowsePath=[QualifiedName("Message")],
                    AttributeId=AttributeIds.Value,
                    TypeDefinitionId=NodeId(ObjectIds.BaseEventType),
                ),
                SimpleAttributeOperand(
                    BrowsePath=[QualifiedName("ActiveState"), QualifiedName("Id")],
                    AttributeId=AttributeIds.Value,
                    TypeDefinitionId=NodeId(ObjectIds.BaseEventType),
                ),
                SimpleAttributeOperand(
                    BrowsePath=[QualifiedName("ConditionName")],
                    AttributeId=AttributeIds.Value,
                    TypeDefinitionId=NodeId(ObjectIds.BaseEventType),
                ),
            ],
            WhereClause=content_filter,
        )
        ev = NodeId(ObjectIds.AlarmConditionType)
        await clientSubs.subscribe_events(evLogNS, ev, filt, 0)

[danmoser]

Hi folks!

• We are running a TwinCAT simulator server. No actual hardware is needed (but I don't know how the simulator licensing works).
• The code @schroeder- suggested did not change the bevahior/output (I'm only getting an additional log line INFO:asyncua.client.ua_client.UaClient:create_monitored_items)
• The eventType displayed in UaExpert is "NodeId". More details in the image below:
  
• Interestingly, I'm able to receive the Events using an open62541 client. Some of the code below. Note that the client doesn't get the nodeId of the EventLogger!
• Using the same open62541 client, I don't receive Events from an asyncua server (replicating the nodeset IDs).

static void
deleteSubscriptionCallback(UA_Client *client, UA_UInt32 subscriptionId, void *subscriptionContext) {
  UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
	      "Subscription Id %u was deleted", subscriptionId);
}

static UA_SimpleAttributeOperand *
setupSelectClauses(void) {
    UA_SimpleAttributeOperand *selectClauses = (UA_SimpleAttributeOperand*)
        UA_Array_new(nSelectClauses, &UA_TYPES[UA_TYPES_SIMPLEATTRIBUTEOPERAND]);
    if(!selectClauses)
        return NULL;

    for(size_t i =0; i<nSelectClauses; ++i) {
        UA_SimpleAttributeOperand_init(&selectClauses[i]);
    }

    selectClauses[0].typeDefinitionId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEEVENTTYPE);
    selectClauses[0].browsePathSize = 1;
    selectClauses[0].browsePath = (UA_QualifiedName*)
        UA_Array_new(selectClauses[0].browsePathSize, &UA_TYPES[UA_TYPES_QUALIFIEDNAME]);
    if(!selectClauses[0].browsePath) {
        UA_SimpleAttributeOperand_delete(selectClauses);
        return NULL;
    }
    selectClauses[0].attributeId = UA_ATTRIBUTEID_VALUE;
    selectClauses[0].browsePath[0] = UA_QUALIFIEDNAME_ALLOC(0, "Message");

    selectClauses[1].typeDefinitionId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEEVENTTYPE);
    selectClauses[1].browsePathSize = 1;
    selectClauses[1].browsePath = (UA_QualifiedName*)
        UA_Array_new(selectClauses[1].browsePathSize, &UA_TYPES[UA_TYPES_QUALIFIEDNAME]);
    if(!selectClauses[1].browsePath) {
        UA_SimpleAttributeOperand_delete(selectClauses);
        return NULL;
    }
    selectClauses[1].attributeId = UA_ATTRIBUTEID_VALUE;
    selectClauses[1].browsePath[0] = UA_QUALIFIEDNAME_ALLOC(0, "Severity");

    return selectClauses;
}

static void
handler_events(UA_Client *client, UA_UInt32 subId, void *subContext,
               UA_UInt32 monId, void *monContext,
               size_t nEventFields, UA_Variant *eventFields) {

  UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
	      "******************** Notification **********************");
  
  /* The context should point to the monId on the stack */
  UA_assert(*(UA_UInt32*)monContext == monId);
  
  for(size_t i = 0; i < nEventFields; ++i) {
    if(UA_Variant_hasScalarType(&eventFields[i], &UA_TYPES[UA_TYPES_UINT16])) {
      UA_UInt16 severity = *(UA_UInt16 *)eventFields[i].data;
      UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Severity: %u", severity);
    } else if (UA_Variant_hasScalarType(&eventFields[i], &UA_TYPES[UA_TYPES_LOCALIZEDTEXT])) {
      UA_LocalizedText *lt = (UA_LocalizedText *)eventFields[i].data;
      UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
		  "Message: '%.*s'", (int)lt->text.length, lt->text.data);
    }
    else {
#ifdef UA_ENABLE_TYPEDESCRIPTION
      UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                        "Don't know how to handle type: '%s'", eventFields[i].type->typeName);
#else
            UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                        "Don't know how to handle type, enable UA_ENABLE_TYPEDESCRIPTION "
                        "for typename");
#endif
        }
    }
}

// ...

    UA_CreateSubscriptionRequest request = UA_CreateSubscriptionRequest_default();
    UA_CreateSubscriptionResponse response =
      UA_Client_Subscriptions_create(client, request, NULL, NULL, deleteSubscriptionCallback);

    UA_UInt32 subId = response.subscriptionId;

    UA_MonitoredItemCreateRequest item;
    UA_MonitoredItemCreateRequest_init(&item);
    item.itemToMonitor.nodeId = UA_NODEID_NUMERIC(0, 2253); // Root->Objects->Server
    item.itemToMonitor.attributeId = UA_ATTRIBUTEID_EVENTNOTIFIER;
    item.monitoringMode = UA_MONITORINGMODE_REPORTING;
    
    UA_EventFilter filter;
    UA_EventFilter_init(&filter);
    filter.selectClauses = setupSelectClauses();
    filter.selectClausesSize = nSelectClauses;

    item.requestedParameters.filter.encoding = UA_EXTENSIONOBJECT_DECODED;
    item.requestedParameters.filter.content.decoded.data = &filter;
    item.requestedParameters.filter.content.decoded.type = &UA_TYPES[UA_TYPES_EVENTFILTER];    

    UA_UInt32 monId = 0;

    UA_MonitoredItemCreateResult result =
      UA_Client_MonitoredItems_createEvent(client, subId,
					   UA_TIMESTAMPSTORETURN_BOTH, item,
					   &monId, handler_events, NULL);

[danmoser]

PS: I've checked the namespace, and there is no NodeId(4200, 8).

[danmoser]

PS2: The TwinCAT server is generating the same events from both NodeId(2253, 0) and NodeId("EventLogger", 8). This explain how open62541 is getting the Events without the logger nodeId, but I still can't get the Events seen in UaExpert with an asyncua client.

[danmoser]

PS3: The doubled logger nodes also explains why I wasn't getting Events with the open62541 client from an asyncua server.

[danmoser]

PS4: NodeId(4200, 8) doesn't exists, but NodeId(4200, 5). It is a BaseEventType child:

[danmoser]

I became aware that this is a known problem. Issue #573 describes a very similar behavior for CodeSys (instead of TwinCAT).

What I'm doing to have all events from the server is skipping (commenting out) evfilter.WhereClause inside get_filter_from_event_type() - - file asyncua/common/events.py.

IMO, the no-filtering option should be configurable by the user in the client interface.

[danmoser]

PS: Related discussion is here: #572

[schroeder-]

The Eventfilter thing is tricky. Thats why, most sdks wants to user to provide a complete Eventfilter. Your autogenerated filter is magic, which is good for most cases. Maybe we should provide the same filter WhereClause as UAExpert is using? Because a optional parameter, will still cause Issue reports.

[schroeder-]

My take on this: #1215

[schroeder-]

aExpert is providing an empty WhereClause so this should be fine.

[schroeder-]

Ok I checked our WhereClause generator. Which generates wrong WhereClauses. If you pass BaseEventType only Events of BaseEventType the first SubEvents, like AuditEventType. If the server generates a Event with the SubEvent of AuditEvent. The server will filter it out because of our WhereClause.

[danmoser]

Thank you for #1215 !!

[schroeder-]

Never mind I was wrong. But our EventFilter is so big no wonder, the server has a problem with it.