[APMAnalytics load] and [GTMSessionUploadFetcher load] take too much time at app startup

[shanksGuo]

Feature proposal

• Firebase Component: APMAnalytics, GTMSessionUploadFetcher

I found [APMAnalytics load] and [GTMSessionUploadFetcher load] method take long time to execute, in my case, when app launches, [APMAnalytics load] takes 51ms and [GTMSessionUploadFetcher load] takes 95ms. see the pic below. I wish you can remove +load method considering Apple is not recommend +load.
By the way, there were too many +load method in firebase and related sdk, such as #6902 #6855 , I wonder if it is possible remove all +load to keep code in control

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[maksymmalyhin]

@shanksGuo Thank you for the report. Appreciate your time spent detailed investigation!

As for +load methods usage by Firebase: for most of the cases the method Firebase classes implement it to register an SDK dependency with the Firebase component system. Completely removing the code from +load methods would make Firebase initialization much more involving process for developers. I think instead we should:
1.concentrate on moving any unnecessary and slow operation (like ones in the issues) out of the +load method
2. Set up startup testing on CI to prevent regressions in the future.

We will work on these items. Sorry for troubles.

[maksymmalyhin]

I updated the title to better represent the issue and intended action items.

[maksymmalyhin]

Analytics part is tracked internally at b/173110496.

[shanksGuo]

@maksymmalyhin Thanks for your efforts, and I wonder which release version will these items be merged?

[maksymmalyhin]

@shanksGuo Sorry for the delayed response. The GTMSessionUploadFetcher issue should be fixed by google/gtm-session-fetcher#219. It can be tested from the branch - add the following line to the Podfile:

pod 'GTMSessionFetcher', :git=>'https://github.com/maksymmalyhin/gtm-session-fetcher.git', :branch=>'mm/load-optimization'

The Analytics issue fix is still in progress. @htcgh may provide more detailed update on it.