Document Contexts.trace

[marandaneto]

https://develop.sentry.dev/sdk/event-payloads/contexts/

Apparently, it's the same as a Span, that's what I learn here https://develop.sentry.dev/sdk/event-payloads/transaction/#contextstrace
if so, it'd be nice to add an Entry to the Contexts page and link to the Spans one

@brustolin

[marandaneto]

@rhcarvalho could you confirm that? thanks.

[rhcarvalho]

Similar fields, but not the same as a span. The trace context contains data about the transaction ("transaction span", "root span" of a tree).

[marandaneto]

I see

A Transaction has to have a specific contexts.trace entry that contains data from the Span.

so Ideally we'd need to document properly what a Contexts.trace really is (field by field)

[rhcarvalho]

In terms of fields, fields-of(transaction) = fields-of(span) + "name"; I think it would be clearer documenting how to map from a transaction to an event. Each transaction field from its in-memory representation maps to some part of the pre-existing event type.

[rhcarvalho]

One specific point that needs clarification is where the span.data goes for the root span / transaction.

• Relay doesn't know about TraceContext.data nor Event.data:
  • https://github.com/getsentry/relay/blob/0143ba7c2556315a2836acdb3cfc2112167e9edc/relay-general/src/protocol/contexts.rs#L442-L468
  • https://github.com/getsentry/relay/blob/master/relay-general/src/protocol/event.rs#L168-L490
• JS SDK sends data in TraceContext:
  • https://github.com/getsentry/sentry-javascript/blob/e9e1525da6b5a346fc259ab7df19415d73f2647e/packages/tracing/src/span.ts#L290-L302
• Python SDK ignores span.data of the root span/transaction (as of writing):
  • https://github.com/getsentry/sentry-python/blob/1d75da5203bdfaa47e920f5d749b85abff5f07f7/sentry_sdk/tracing.py#L543-L553
  • https://github.com/getsentry/sentry-python/blob/1d75da5203bdfaa47e920f5d749b85abff5f07f7/sentry_sdk/tracing.py#L454-L466

Sentry UI can deal with either arbitrary unknown fields in TraceContext as well as Event.Extra:

[rhcarvalho]

Note: I was not able to make the UI show data for the root span in the same way that it shows for child spans:

[rhcarvalho]

I see we got a bit side-tracked in the conversation here.

Copying from getsentry/sentry-cocoa#1065 (comment) below

---

The trace context is just part of the transaction that is not a top-level event field.

See https://github.com/getsentry/sentry-go/blob/57123a409be55f61b1d5a6da93c176c55a399ad0/tracing.go#L313-L352.

The fields are:

TraceID
SpanID
ParentSpanID
Op
Description
Status

And note that SpanContext (as described in the spec as a data bag for spans) != TraceContext.

[marandaneto]

@rhcarvalho on Java, the SpanContext has the addition of 2 fields, sampled and tags

[rhcarvalho]

If Java is sending those in the "trace context" Relay will accept it (as it accepts unknown keys for forward-compatibility) but it has no use, so just wasting bytes.

[bruno-garcia]

Relates to #320

[marandaneto]

https://develop.sentry.dev/sdk/event-payloads/types/#tracecontext