[exporter/azuremonitor] Why span events are pushed as traces and not as custom events?

[ghost]

Component(s)

exporter/azuremonitor

Describe the issue you're reporting

Azure Monitor supports custom events: https://learn.microsoft.com/en-us/azure/azure-monitor/app/api-custom-events-metrics#trackevent

I wonder why span events are pushed as traces and not as custom events by the Azure Monitor exporter?

opentelemetry-collector-contrib/exporter/azuremonitorexporter/trace_to_envelope.go

Line 148 in 169ac6c

messageData := spanEventToMessageData(spanEvent)

cc @pcwiese @cijothomas @TylerHelmuth

[github-actions]

Pinging code owners:

• exporter/azuremonitor: @pcwiese

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[cijothomas]

CustomEvents in application insights is not same as SpanEvents, though the name is similar. SpanEvent is more like "logs", except they are always attached to a Span, and this is better mapped as TraceTelemetry, as that is where general "logs" are stored in ApplicationInsights.

This collector component is not an official Microsoft/Azure component, but if you look at the official ones (the java/.net/node/python exporters in Azure repo), they are mapping SpanEvents to TraceTelemetry.

[cijothomas]

Thanks for the explanation. There's no way to produce CustomEvents through OTLP in this case, right?

correct.
(In the future it might be possible with https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/event-api.md, but given that spec is experimental, its hard to tell now).

[crobert-1]

@cakescience Is there anymore information needed here? Just want to make sure it's safe to close this issue.