Detect messaging.{system,operation} in TranslateTransaction

[carsonip]

Use messaging.system and messaging.operation to detect OTel messaging span in TranslateTransaction. The corresponding handling already exists in TranslateSpan.

Closes #194

[carsonip]

[For reviewer] As demonstrated by the test case, this is a new case that doesn't exist before. When messaging.system or messaging.operation is present AND messaging.destination is absent, do we want event.Transaction.Message to be empty or nil? Does it make a difference?

To rephrase the question, is it ok to have event.Transaction.Message == nil when event.Transaction.Type == "messaging"?

[simitt]

Yes; this PR fixes the bug that the transaction type is not set although messaging attributes are sent.
However, the apm message model is pretty outdated compared to the otel messaging spec. So my suggestion would be to open a follow up github issue for updating the supported semconv version and then also update the messaging model definition. I'd see it outside the scope of this PR though.

[carsonip]

[For reviewer] Note: IMO there are still quite a few cases where we are doing allocs in this function, when we should use vt pool instead. This change fixes one.

[simitt]

I saw the improvement - it would make sense to open a tech debt issue, collecting places where allocations could be reduced.

[carsonip]

Moved this code back here. It is important to overwrite existing event.Transaction.Message to avoid breaking otel bridge test when event.Transaction.Message and the otel attribute exist at the same time.

=== RUN   TestDecodeMapToTransactionModel/otel-bridge/messaging
    transaction_test.go:559: 
                Error Trace:    /home/carson/projects/apm-data/input/elasticapm/internal/modeldecoder/v2/transaction_test.go:559
                Error:          Not equal: 
                                expected: &modelpb.Message{state:impl.MessageState{NoUnkeyedLiterals:pragma.NoUnkeyedLiterals{}, DoNotCompare:pragma.DoNotCompare{}, DoNotCopy:pragma.DoNotCopy{}, atomicMessageInfo:(*impl.MessageInfo)(nil)}, sizeCache:0, unknownFields:[]uint8(nil), Body:"", Headers:[]*modelpb.HTTPHeader(nil), AgeMillis:(*uint64)(nil), QueueName:"myQueue", RoutingKey:""}
                                actual  : &modelpb.Message{state:impl.MessageState{NoUnkeyedLiterals:pragma.NoUnkeyedLiterals{}, DoNotCompare:pragma.DoNotCompare{}, DoNotCopy:pragma.DoNotCopy{}, atomicMessageInfo:(*impl.MessageInfo)(nil)}, sizeCache:0, unknownFields:[]uint8(nil), Body:"init", Headers:[]*modelpb.HTTPHeader{(*modelpb.HTTPHeader)(0xc00040aa50)}, AgeMillis:(*uint64)(0xc000327058), QueueName:"myQueue", RoutingKey:"init"}

[simitt]

I don't see how the message instance would already be non-nil at this point for otel data, so it should be fine.

[simitt]

I don't see how the message instance would already be non-nil at this point for otel data, so it should be fine.

[simitt]

Tested with BC 5 and adapting the sendotlp app in apm-server, to send certain messaging attributes. The expected behavior was observed, that spans and transactions had type messaging set, in all cases, and when messaging.destination was set, the queue.name was also set.

test code for transaction

cfg := trace.NewSpanStartConfig(trace.WithSpanKind(trace.SpanKindProducer))
attrs := append(cfg.Attributes(),
  attribute.String("messaging.system", "kafka"),
  attribute.String("messaging.destination", "aws-msk"))
ctx, parent := tracer.Start(ctx, "parent-message", trace.WithAttributes(attrs...))

test code for span:

opt := trace.WithSpanKind(trace.SpanKindConsumer)
cfg = trace.NewSpanStartConfig(opt)
attrs = append(cfg.Attributes(),
  // attribute.String("messaging.system", "kafka"),
  // attribute.String("messaging.operation", "consume"),
  attribute.String("messaging.destination", "aws-msk"),
)
_, child1 := tracer.Start(ctx, "child1-message-destination", trace.WithAttributes(attrs...))