ReplaySubject leaks subscribers even after unsubscribing?

[mttkay]

On Android a common use case is to cache or replay an observable to UI components that might get temporarily destroyed due to e.g. screen rotations.

The biggest challenge on Android when using RxJava is therefore to make sure that no resource leaks occur; since subscribers, however, might be inner classes of an Android Activity or Fragment (if you're unfamiliar: think screen object), those will leak if strong references held within an operator are not released when unsubscribing from the sequence.

I just noticed that when using e.g. cache on a long running sequence, and subscribing and unsubscribing multiple times, the observer I subscribe to the sequence never seems to get finalized. Android's StrictMode indeed reports that the observer (and hence the entire screen) is being leaked:

E/StrictMode( 2791): class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=2; limit=1
E/StrictMode( 2791): android.os.StrictMode$InstanceCountViolation: class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=2; limit=1
E/StrictMode( 2791): class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=3; limit=1
E/StrictMode( 2791): android.os.StrictMode$InstanceCountViolation: class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=3; limit=1
E/StrictMode( 2791): class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=4; limit=1
E/StrictMode( 2791): android.os.StrictMode$InstanceCountViolation: class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=4; limit=1
E/StrictMode( 2791): class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=5; limit=1
E/StrictMode( 2791): android.os.StrictMode$InstanceCountViolation: class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=5; limit=1
E/StrictMode( 2791): class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=6; limit=1
E/StrictMode( 2791): android.os.StrictMode$InstanceCountViolation: class com.netflix.rxjava.android.samples.RetainedCacheFragmentActivity; instances=6; limit=1

I quickly glanced over the ReplaySubject subscription handling code, and it looks as if on unsubscribe, it removes the observer from the internal map; maybe that's broken, however?

[devisnik]

We're observing the leakage on replaying as well (using version 0.17.0-RC7).

It seems that ReplaySubject uses some replayState map within its ReplayState that keeps references to the subscribers.

We currently work around the issue by avoiding (non-static) inner classes as subscribers and voiding references to activity/fragment-bound variables explicitly in onComplete. This of course only minimizes the impact of the leakage.

Any better suggestions of how to handle that?

[akarnokd]

I think this issue and some related problems with ReplaySubject are now fixed. Could you confirm & close this issue?

[mttkay]

I can confirm this is fixed for us.

[benjchristensen]

Thanks @mttkay for the confirmation.