Prevent ANR during SDK initialization

[ansman]

Description

When initializing the OpenTelemetry Android SDK with disk buffering enabled, we discovered that synchronous disk space checks were causing ANRs in production. These checks occur during the creation of disk buffering exporters, specifically in DiskManager.getMaxFolderSize(), which makes blocking IPC calls through StorageManager.getAllocatableBytes() on the main thread. The issue manifests in the following ANR stacktrace:

android.os.BinderProxy.transact (BinderProxy.java:662)
android.os.storage.IStorageManager$Stub$Proxy.getAllocatableBytes (IStorageManager.java:2837)
android.os.storage.StorageManager.getAllocatableBytes (StorageManager.java:2414)
android.os.storage.StorageManager.getAllocatableBytes (StorageManager.java:2404)
io.opentelemetry.android.internal.services.CacheStorage.getAvailableSpace (CacheStorage.java:66)
io.opentelemetry.android.internal.services.CacheStorage.ensureCacheSpaceAvailable (CacheStorage.java:50)
io.opentelemetry.android.internal.features.persistence.DiskManager.getMaxFolderSize (DiskManager.kt:58)
io.opentelemetry.android.OpenTelemetryRumBuilder.createStorageConfiguration (OpenTelemetryRumBuilder.java:338)
io.opentelemetry.android.OpenTelemetryRumBuilder.build (OpenTelemetryRumBuilder.java:286)

Solution

To fix this we moved initialization to run on a background executor and buffer the data in memory until it completes.

The process works like this:

1. Initialize the SDK with BufferDelegatingExporter instances that can immediately accept telemetry data.
2. Move exporter initialization off the main thread.
3. Once async initialization completes, flush buffered signals to initialized exporters and delegate all future signals.

The primary goal of this solution is to be unobtrusive and prevent ANRs caused by initialization of disk exporters, while preventing signals from being dropped.

Testing

We have added unit tests to cover the buffering, delevation, and RUM building. We've also verified this with both disk enabled and disk disabled.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ansman / name: Nicklas Ansman (ce6d6f7, 5c4f0e5, a0eef40, e457cee)

[ansman]

FYI we are working on getting the CLA signed.

[ansman]

@breedx-splk CLA signed

[breedx-splk]

Thanks @ansman for taking this on, I think this is going to be really helpful...and there are bound to be a few other areas that are problematic at startup, so I appreciate you both shining some light on this and for going the distance in submitting this PR.

[LikeTheSalad]

Thank you for taking the time to contribute 🙏 I like the overall idea. I left some questions and suggestions, so please have a look when you get a chance.

[ansman]

I've updated the PR with the feedback and everything except the logging has been addressed.

In addition the returned result will not be success any longer but rather resolve when the delegate is set.

[breedx-splk]

Thanks @ansman for sticking this out, I like how it's come together! Would still like to see the log warning emitted, and I'll wait to let @LikeTheSalad do the merge with his approval, but I think things are looking solid now. Thanks for the contribution.

[LikeTheSalad]

Thank you for your contribution and patience, @ansman! 🙏 I'm looking forward to getting your PR merged, though it looks like there are some formatting issues that are making the build fail, if you could please update this PR after running ./gradlew spotlessApply locally, I think that should do. I'm happy to proceed with the merge once the GH build passes :)