[Sentry] App Start span doesn't have nudge_migration_cohort

[rlinoz]

Problem:
The spans that track app start time don't contain the
nudge_migration_cohort tag, which makes us blind to that metric for specific cohorts.

Solution:
Investigate why that happens and fix it.

https://expensify.sentry.io/explore/traces/?environment=production&environment=staging&field=id&field=span.name&field=span.description&field=span.duration&field=transaction&field=timestamp&field=nudge_migration_cohort&project=4510228107427840&query=span.name%3A%EF%80%8DContains%EF%80%8Dapp.start.cold%20has%3Anudge_migration_cohort&statsPeriod=14d

[sosek108]

@rinej could you paste here the summary of what we already know about this issue?

[rinej]

Sure! Adding the update and some initial research (also posted on the slack thread)

So it looks that we don’t see any nudge_migration_cohort tags on app.start.cold / app.start.warm because the
app.start.* transactions are created natively.
They start when the OS launches the app and finish at the first frame render. At that point, JS is not running yet, so any tags added in JS are not applied.

What we tried:
We attempted to enrich events with tags before sending them to Sentry
As it seems this approach does not work for native events
Pr with potential fix -> #77771

Ideas for fix:
1.Add the nudge tag in native code (for iOS and Android)
We would need to add the custom logic for adding it.Also will need to initialize Sentry SDK in the native layer before -> #73302

2.Use alternative startup metrics with JS-level tags
We already have two startup-related metrics that support JS tags: ManualAppStartup and ui.load
The issues with them is that these spans sometimes never close (e.g. app goes to background), this results that some of them has long durations (minutes or even hours). BUT we could filter out long spans and assume e.g. span.duration < 1 min = valid startup.
This gives us a approximation of startup performance and could compare cohorts and track trends over time
It is not perfect, but metric are already there

The example dashboard with those metrics:
ManualAppStartup (filtered to < 1 min) and ui.load (filtered to < 1 min)
https://expensify.sentry.io/dashboard/210279/?environment=production&statsPeriod=7d

[rlinoz]

Hey @rinej are you working on this one? Just to be sure, so I can assign you.

[rinej]

yes, please do

[rinej]

I'm still investigating. Might be necessary to initialize Sentry SDK in the native layer before.

On the other hands we have the user details in all spans, so in theory the nudge tag should be there as well.

Meanwhile we can use that dashboard for nudge_migration app start metric:
dashboard

[melvin-bot]

@rinej, @rlinoz Whoops! This issue is 2 days overdue. Let's get this updated quick!

[rlinoz]

@rinej is looking this 🙌