How to measure long custom transaction at application startup?

[czterystaczwarty]

Hi,

We have a complex microfrontend application (platform and multiple micro-applications maintained by different teams).
I'm trying to use Sentry to measure application startup time from loading the HTML to starting the framework to loading data in one of the micro-apps.

Is it possible to make long custom transaction (span) between many javascript files and scopes, with transaction navigation in between and add custom measurement to it?

Or in another way:
How to add measurement anywhere in the application so that it is added to some transaction to find it in Discover tab and create query or widget to track it over time.

I tried just Sentry.setMeasurement but it isn't added to any transaction. It seems to me that all transactions have already completed and been sent.

In other (much simpler) app I just wrapped long async function with Sentry.setManualSpan and attach measurement to it by Sentry.setMeasurement.
In this case it's easy to measure startup time by performance.mark and performance.measure but I struggle with sending it to Sentry meaningful, searchable way.

[AbhiPrasad]

@czterystaczwarty - check out Sentry metrics: https://sentry.io/lp/metrics/, this may fit the use case you need better.

[czterystaczwarty]

Finally, I added perdormance.mark in the HTML document from which I deduct metrics and turned off instrumentNavigation in browserTracingIntegration so that navigation would not interfere with pageload (initial) transaction.
Now I have long transactions with metrics that interest me.