Tracing is seperate in Vnodes.

[Terni]

Hi skywalking team.
I have a problem with the tracing sequence. VNode is separate, I don't know how to fix it.

Sender with ExitSegmentContext:

    public virtual void BeforeTransportSend(object value)
    {
        if (value is not RabbitMqSendContext mqSendContext)
        {
            return;
        }

        try
        {
            string operationName = value.GetType().IsGenericType
                ? value.GetType().GetGenericArguments().First().Name
                : mqSendContext.Exchange;

            string networkAddrerss = mqSendContext.SourceAddress?.ToString() ?? string.Empty;
            var brokerAddress = new BrokerAddress(MqComponent, networkAddrerss);

            var headerCollection = new TextCarrierHeaderCollection(new Dictionary<string, string>());
            SegmentContext exitSegmentContext = _tracingContext.CreateExitSegmentContext($"Send_{operationName}", networkAddrerss, headerCollection);

            var correlationId = mqSendContext.CorrelationId?.ToString() ?? string.Empty;
            
            exitSegmentContext.Span.Component = GetComponent(brokerAddress, true);
            exitSegmentContext.Span.SpanLayer = SpanLayer.MQ;
            exitSegmentContext.Span.Peer = brokerAddress.Endpoint;
            exitSegmentContext.Span.AddTag(Tags.MQ_TOPIC, operationName);
            exitSegmentContext.Span.AddTag(Tags.MQ_BROKER, HostBroker);
            exitSegmentContext.Span.AddTag("CorrelationId", correlationId);
            exitSegmentContext.Span.AddTag("MessageId", mqSendContext.MessageId?.ToString() ?? string.Empty);
            exitSegmentContext.Span.AddTag("RequestId", mqSendContext.RequestId?.ToString() ?? string.Empty);
            
            if (mqSendContext.MessageId != null)
            {
                _contexts[mqSendContext.MessageId.Value] = exitSegmentContext;
            }

            if (!headerCollection.AnySafe())
            {
                return;
            }

            foreach (var (key, headerVal) in headerCollection)
            {
                mqSendContext.Headers.Set(key, headerVal);
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to process MassTransit diagnostic event!");
        }
    }

    public virtual void AfterTransportSend(object value)
    {
        if (value is not RabbitMqSendContext mqSendContext)
        {
            return;
        }
        
        if (mqSendContext.MessageId != null && _contexts.TryRemove(mqSendContext.MessageId.Value, out var exitContext))
        {
            _tracingContext.Release(exitContext);
        }
    }

Receiver with EntrySegmentContext:

    public virtual void BeforeConsumerHandle(object value)
    {
        if (value is not ConsumeContext consumeContext)
        {
            return;
        }

        try
        {
            //only string headers are supported by SW
            IEnumerable<KeyValuePair<string, string>> headerPair = consumeContext.Headers
                .GetAll()
                .Select(header => new KeyValuePair<string, string>(header.Key, header.Value.ToString()));
            var headerCollection = new TextCarrierHeaderCollection(headerPair);
            string networkAddress = consumeContext.SourceAddress?.ToString() ?? string.Empty;
            var brokerAddress = new BrokerAddress(MqComponent,networkAddress);
            
            string operationName = value.GetType().IsGenericType ? value.GetType().GetGenericArguments().First().Name : networkAddress;
            SegmentContext entrySegmentContext = _tracingContext.CreateEntrySegmentContext($"Handle_{operationName}", headerCollection);
            
            entrySegmentContext.Span.Component = GetComponent(brokerAddress, false);
            entrySegmentContext.Span.SpanLayer = SpanLayer.MQ;
            entrySegmentContext.Span.Peer = brokerAddress.Endpoint;
            entrySegmentContext.Span.AddTag("CorrelationId", consumeContext.CorrelationId?.ToString() ?? string.Empty);
            entrySegmentContext.Span.AddTag("MessageId", consumeContext.MessageId?.ToString() ?? string.Empty);
            entrySegmentContext.Span.AddTag("RequestId", consumeContext.RequestId?.ToString() ?? string.Empty);
            
            if (consumeContext.MessageId != null)
            {
                _contexts[consumeContext.MessageId.Value] = entrySegmentContext;
            }
            
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to process MassTransit diagnostic event!");
        }
    }

And last version skywalking 9.1.0 in server-oap. I saw this error

2022-06-22 10:05:27,149 org.apache.skywalking.oap.server.receiver.trace.provider.handler.v8.grpc.TraceSegmentReportServiceHandler 75 [grpcServerPool-1-thread-15] ERROR [] - [9.1.0-f1f519c] null
java.lang.NullPointerException: null
at org.apache.skywalking.oap.server.core.source.EndpointRelation.prepare(EndpointRelation.java:101) ~[server-core-9.1.0.jar:9.1.0]
at org.apache.skywalking.oap.server.core.analysis.DispatcherManager.forward(DispatcherManager.java:59) ~[server-core-9.1.0.jar:9.1.0]
at org.apache.skywalking.oap.server.core.source.SourceReceiverImpl.receive(SourceReceiverImpl.java:36) ~[server-core-9.1.0.jar:9.1.0]
at org.apache.skywalking.oap.server.analyzer.provider.trace.parser.listener.EndpointDepFromCrossThreadAnalysisListener.lambda$build$0(EndpointDepFromCrossThreadAnalysisListener.java:130) ~[agent-analyzer-9.1.0.jar:9.1.0]
at java.util.ArrayList.forEach(Unknown Source) ~[?:?]
at org.apache.skywalking.oap.server.analyzer.provider.trace.parser.listener.EndpointDepFromCrossThreadAnalysisListener.build(EndpointDepFromCrossThreadAnalysisListener.java:124) ~[agent-analyzer-9.1.0.jar:9.1.0

Do I have to set something somewhere?

[wu-sheng]

This seems your private codes on your side. You have the source codes we don't.

About VNode, there is a very clear explanation in the doc about what it is.

[Terni]

Ok I understood.
https://github.com/apache/skywalking/blob/master/docs/en/FAQ/vnode.md
I think about it.

[xlq20080808]

I have the same problem, have you found the cause of the NPE?

[Terni]

I solved it. The problem was pairing to a different type. I had to remove (Component, SpanLayer, Peer). There is some documentation, but it is very weak. I hope there will be documentation for CreateExitSegmentContext in the future.

[xlq20080808]

I solved this problem by used the main branch code.This is a bug about MQ
#9297 (comment) and fixed by #9300

[Terni]

Thank you. I knew it but nobody help me.