[EPIC] Tag spans if they contribute to TTID / TTFD

[markushi]

Idea: Identify spans as TTID or TTFD contributing spans to narrow down which spans actively contribute to screen load times.

Use the ui.contributes_to_ttid and ui.contributes_to_ttfd boolean flags to indicate if a span contributes or not.

See Notion doc for details:
https://www.notion.so/sentry/Data-Requirements-b4f616bac8bc449096a765f915e0a209?p=9b5a0979a81645789db6877593729cf4&pm=s

Tasks

Preview Give feedback

1. [Starfish] Tag spans if they contribute to TTID / TTFD sentry-java#3252
   Platform: Android +1
   
2. Tag spans if they contribute to TTID / TTFD sentry-dart#2524
   Platform: Dart +1
3. Cocoa
4. React-Native

[philipphofmann]

The screen load transactions should already contain all the information to determine which spans contribute to TTID/TTFD. Do you think further changes are required, @markushi?

[markushi]

The screen load transactions should already contain all the information to determine which spans contribute to TTID/TTFD. Do you think further changes are required, @markushi?

In the advent of span-only I don't think we have a guarantee that all required spans will be sent over in a single txn. Thus it could make sense to calculate those two fields on the SDK side.

@shruthilayaj what do you think about this?

[kahest]

@markushi this is done on the backend already, right? Do we need this on the SDK side still?

[markushi]

@markushi this is done on the backend already, right? Do we need this on the SDK side still?

Nope, as far as I know there's no implementation for this on the backend side. Looking at the Java PR the implementation is not straightforward and needs additional context (e.g. ttid is only main thread spans, whilst ttfd isn't) so I strongly suggest to implement this on the SDK side.

[markushi]

As discussed internally we want to calculate the contribution flags on the backend. Closing this for now, as it's not relevant anymore. To ensure this is not lost, I've added it as a post GA item to getsentry/sentry#75120