Memory Leak from the AWSAppSyncClient

[dy08]

What happened:
When working off from the official sample app, aws-mobile-appsync-events-starter-android,
I kept getting memory leaks from the AWSAppSyncClient instance,
which is declared as a static volatile variable in ClientFactory.java.

In com.amazonaws.postsapp:1.0:1.
* com.amazonaws.postsapp.PostsActivity has leaked:
* GC ROOT static com.amazonaws.postsapp.ClientFactory.client
* references com.amazonaws.mobileconnectors.appsync.AWSAppSyncClient.mApolloClient
* references com.apollographql.apollo.ApolloClient.subscriptionManager
* references com.amazonaws.mobileconnectors.appsync.subscription.RealSubscriptionManager.subscriptionsById
* references java.util.HashMap.table
* references array java.util.HashMap$HashMapEntry[].[11]
* references java.util.HashMap$HashMapEntry.value
* references com.amazonaws.mobileconnectors.appsync.subscription.SubscriptionObject.listeners
* references java.util.HashSet.backingMap
* references java.util.HashMap.table
* references array java.util.HashMap$HashMapEntry[].[0]
* references java.util.HashMap$HashMapEntry.key
* references com.amazonaws.postsapp.PostsActivity$3.this$0 (anonymous implementation of com.amazonaws.mobileconnectors.appsync.AppSyncSubscriptionCall$Callback)
* leaks com.amazonaws.postsapp.PostsActivity instance

AppSync SDK Versions tried : 2.6.16 & 2.6.19

What I have tried:

• Setting the AWSAppSyncClient to null on Activity's onDestroy method.
  --> This solved the memory leak from the AwsAppSyncClient instance.
  --> But I got more memory leaks from
  1. AppSyncOfflineMutationManager, which references mContext

In com.amazonaws.postsapp:1.0:1.
* com.amazonaws.postsapp.PostsActivity has leaked:
* GC ROOT android.os.HandlerThread.<Java Local>
* references com.amazonaws.mobileconnectors.appsync.AppSyncOfflineMutationManager$NetworkUpdateHandler.this$0
* references com.amazonaws.mobileconnectors.appsync.AppSyncOfflineMutationManager.mContext
* leaks com.amazonaws.postsapp.PostsActivity instance

2. ThreadPoolExecutor in ApolloClient.Builder's SubscriptionManager, which references Activity

(I guess I can pass in a custom Executor when instantiating an AWSAppSyncClient instance, but I couldn't figure out quite how to do this)

In com.amazonaws.postsapp:1.0:1.
* com.amazonaws.postsapp.PostsActivity has leaked:
* GC ROOT thread java.lang.Thread.<Java Local> (named 'Apollo Dispatcher')
* references java.util.concurrent.ThreadPoolExecutor.threadFactory
* references com.apollographql.apollo.ApolloClient$Builder$1.this$0 (anonymous implementation of java.util.concurrent.ThreadFactory)
* references com.apollographql.apollo.ApolloClient$Builder.subscriptionManager
* references com.amazonaws.mobileconnectors.appsync.subscription.RealSubscriptionManager.subscriptionsById
* references java.util.HashMap.table
* references array java.util.HashMap$HashMapEntry[].[4]
* references java.util.HashMap$HashMapEntry.value
* references com.amazonaws.mobileconnectors.appsync.subscription.SubscriptionObject.listeners
* references java.util.HashSet.backingMap
* references java.util.HashMap.table
* references array java.util.HashMap$HashMapEntry[].[0]
* references java.util.HashMap$HashMapEntry.key
* references com.amazonaws.postsapp.PostsActivity$3.this$0 (anonymous implementation of com.amazonaws.mobileconnectors.appsync.AppSyncSubscriptionCall$Callback)
* leaks com.amazonaws.postsapp.PostsActivity instance

Some parts of the code in the SDK hold on to the references to the Context.

• Most of these seem to come from the Handler or Thread related classes

I can't think of a good way to clear these references for the garbage collection to work correctly when the application is finished. Would making the SDK receive a WeakReference of Context be a solution to this problem?

If there are errors in the way I set up my project or my understanding of the code is incorrect,
please let me know.

[minbi]

Thanks for the detailed report. We will look into removing these references as much as possible.

[minbi]

We should have patched the issues here in version 2.6.20. Re-open if necessary

[dy08]

Hello,
I have been getting memory leaks from 2.6.20 as well.
One of the lines point to AppSyncOfflineMutationInterceptor.java line # 223
this.mContext =context;
I don't see any reuse of this variable, so please take time to see if this can be removed.

[minbi]

We will look into removing this in the next release.

[minbi]

Please see version 2.6.21