Move the signalsBufferDir under context.getFilesDir()

[bencehornak]

At the moment the signalsBufferDir, which is used to store un-exported telemetry batches, is stored within context.getCacheDir():

opentelemetry-android/core/src/main/java/io/opentelemetry/android/internal/features/persistence/DiskManager.kt

Lines 20 to 25 in a317b11

	val signalsBufferDir: File
	get() {
	val dir = File(cacheStorage.cacheDir, "opentelemetry/signals")
	ensureExistingOrThrow(dir)
	return dir
	}

opentelemetry-android/services/src/main/java/io/opentelemetry/android/internal/services/CacheStorage.java

Lines 24 to 26 in a317b11

	public File getCacheDir() {
	return appContext.getCacheDir();
	}

According to the docs there are no persistency guarantees for context.getCacheDir():

The system will automatically delete files in this directory as disk space is needed elsewhere on the device.

For those applications, where telemetry is a nice-to-have this sounds like an acceptable trade-off. In my case I cannot afford to lose telemetry because of the internal quirks of the OS, as there might be important business events standing in the device's queue.

So my recommendation is to move the signalsBufferDir under the more persistent getFilesDir() to prevent telemetry data loss caused by OS clean-ups.

[marandaneto]

The system will automatically delete files in this directory as disk space is needed elsewhere on the device

This is handled by the OS when using getCacheDir

So I'd say it's better to provide a dir configuration rather than changing it, I think getCacheDir is perfect for telemetry data.
In this case, if you provide a custom dir, you have to deal with that manually.

[bencehornak]

@marandaneto do you mean adding a new property to the DiskBufferingConfig like this?

Before:

opentelemetry-android/core/src/main/java/io/opentelemetry/android/internal/features/persistence/DiskManager.kt

Lines 20 to 25 in a317b11

	val signalsBufferDir: File
	get() {
	val dir = File(cacheStorage.cacheDir, "opentelemetry/signals")
	ensureExistingOrThrow(dir)
	return dir
	}

After:

    val signalsBufferDir: File
        get() {
            val dir = diskBufferingConfig.signalsBufferDir ?: File(cacheStorage.cacheDir, "opentelemetry/signals")
            ensureExistingOrThrow(dir)
            return dir
        }

If yes, I'm fine with that too, that would satisfy my goal too.

[marandaneto]

Yes

[LikeTheSalad]

I agree with @marandaneto and like your proposed solution, @bencehornak. Would you like to contribute it?

[bencehornak]

Sure, I'll implement the new property