NullPointerException, ConflictResolverInterface, Mutation fails

[DeMoss15]

• AppSync SDK Version: 2.7.4
• aws-android-sdk-mobile-client: 2.10.0

caching strategy NETWORK_ONLY

NPE was on previous versions of the sdk too. But there was no queue.
In latest version requests are being just added to this queue and waited for smth.
In previous versions, even after exception, all mutations were being executed.

here is stack trace of NPE:

V/InterceptorCallback: Thread:[13268]: onResponse()
D/InterceptorCallback: Thread:[13268]: onResponse -- found error
D/InterceptorCallback: Thread:[13268]: onResponse -- Got a string match in the errors for "The conditional request failed".
Thread:[13268]: Conflict String: {"__typename":"UserPost","userId":"3ef6eeb7-d1d3-4060-8d2b-1c929ecef914","createdAt":"2019-01-09T13:44:55.388Z","content":"Hello World","authorType":"USER","author":null,"authorStorefront":null}
Thread:[13268]: Client String: {"createdAt":"2019-01-09T13:44:55.388Z"}
D/InterceptorCallback: Thread:[13268]: onCompleted()
2019-01-09 15:33:36.872 12487-12891/com.moja V/QueueUpdateHandler: Thread:[13124]: Got message to take action on the mutation queue.
2019-01-09 15:33:36.872 12487-12891/com.moja D/QueueUpdateHandler: Thread:[13124]: Got message that a originalMutation process needs to be retried.
2019-01-09 15:33:36.873 12487-12891/com.moja V/QueueUpdateHandler: Thread:[13124]: java.lang.NullPointerException: Attempt to invoke interface method 'void com.amazonaws.mobileconnectors.appsync.ConflictResolverInterface.resolveConflict(com.amazonaws.mobileconnectors.appsync.ConflictResolutionHandler, org.json.JSONObject, org.json.JSONObject, java.lang.String, java.lang.String)' on a null object reference
2019-01-09 15:33:36.873 12487-12891/com.moja W/System.err: java.lang.NullPointerException: Attempt to invoke interface method 'void com.amazonaws.mobileconnectors.appsync.ConflictResolverInterface.resolveConflict(com.amazonaws.mobileconnectors.appsync.ConflictResolutionHandler, org.json.JSONObject, org.json.JSONObject, java.lang.String, java.lang.String)' on a null object reference
2019-01-09 15:33:36.874 12487-12891/com.moja W/System.err: at com.amazonaws.mobileconnectors.appsync.AppSyncOfflineMutationInterceptor$QueueUpdateHandler.handleMessage(AppSyncOfflineMutationInterceptor.java:273 )
2019-01-09 15:33:36.874 12487-12891/com.moja W/System.err: at android.os.Handler.dispatchMessage(Handler.java:107 )
2019-01-09 15:33:36.874 12487-12891/com.moja W/System.err: at android.os.Looper.loop(Looper.java:198 )
2019-01-09 15:33:36.874 12487-12891/com.moja W/System.err: at android.os.HandlerThread.run (HandlerThread.java:65 )

whole stack traces:

before:
appsync_version_2,7,4.txt

after:
appsync_version_2,6,28.txt

[scb01]

@DeMoss15

Thank you for reporting this issue. I will look into this and post an update here once I have more information.

[scb01]

@DeMoss15

Version 2.7.5 of the SDK has a fix for this issue. For the Conflict Resolution feature, you have to pass in a custom config resolver. See the following two links for an example of how to do that

aws-mobile-appsync-sdk-android/aws-android-sdk-appsync-tests/src/androidTest/java/com/amazonaws/mobileconnectors/appsync/AppSyncTestSetupHelper.java

Line 98 in 757d8e0

.conflictResolver( new TestConflictResolver())

aws-mobile-appsync-sdk-android/aws-android-sdk-appsync-tests/src/androidTest/java/com/amazonaws/mobileconnectors/appsync/AppSyncTestSetupHelper.java

Line 262 in 757d8e0

static class TestConflictResolver implements ConflictResolverInterface {

Please give it a try and let us know how it goes.

[DeMoss15]

@cbommas

Thank you. There is no NPE anymore.

But now I get onFailure() after successful mutation (using default ConflictResolver)
and then everything work fine again.

timestamp: 2019-01-15 17:35:35.575
stack trace:
appsync_version_2,7,5.txt

[scb01]

@DeMoss15

I took a look at the attached log and this is the expected behavior. It looks like you are not passing in your conflict resolver when you create the AppSync Client. When a conflict resolver is not passed in and a conflict is detected, the default behavior is to fail the mutation and invoke the onError callback method. See below for how you would pass in your conflict resolver

              AWSAppSyncClient.builder()
                .context(context)
                .credentialsProvider(credentialsProvider)
                .serverUrl(endPoint)
                .region(Regions.fromName(appSyncRegion))
                .conflictResolver( YOUR CONFLICT RESOLVER)
                .persistentMutationsCallback(new PersistentMutationsCallback() {
                    @Override
                    public void onResponse(PersistentMutationsResponse response) {
                        Log.d(TAG, response.getMutationClassName());
                    }

                    @Override
                    public void onFailure(PersistentMutationsError error) {
                        Log.e(TAG, error.getMutationClassName());
                        Log.e(TAG, "Error", error.getException());
                    }
                })
           .build();

I am confused by your comment about using the default Conflict Resolver. Can you elaborate?

[DeMoss15]

@cbommas

I've researched this issue again: this error is on our side.
We call the same mutation twice, accidentally.

Thank you very much for your help!)

[DeMoss15]

@cbommas
One more question:

What this logs mean and can I suppose it somehow if it's not important

2019-01-16 16:11:48.565 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]:Persistent mutations queue is EMPTY!. Will check inMemory Queue next
2019-01-16 16:11:48.565 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]: In Memory mutations queue was EMPTY!. Nothing to process, exiting
2019-01-16 16:11:58.606 16346-16550/com.moja V/AppSyncOfflineMutationInterceptor: Thread:[15367]: processing Mutations
2019-01-16 16:11:58.607 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to take action on the mutation queue.
2019-01-16 16:11:58.608 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to process next mutation if one exists.
2019-01-16 16:11:58.613 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]:Persistent mutations queue is EMPTY!. Will check inMemory Queue next
2019-01-16 16:11:58.614 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]: In Memory mutations queue was EMPTY!. Nothing to process, exiting
2019-01-16 16:12:08.649 16346-16550/com.moja V/AppSyncOfflineMutationInterceptor: Thread:[15367]: processing Mutations
2019-01-16 16:12:08.651 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to take action on the mutation queue.
2019-01-16 16:12:08.652 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to process next mutation if one exists.
2019-01-16 16:12:08.660 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]:Persistent mutations queue is EMPTY!. Will check inMemory Queue next
2019-01-16 16:12:08.661 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]: In Memory mutations queue was EMPTY!. Nothing to process, exiting
2019-01-16 16:12:18.693 16346-16550/com.moja V/AppSyncOfflineMutationInterceptor: Thread:[15367]: processing Mutations
2019-01-16 16:12:18.694 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to take action on the mutation queue.
2019-01-16 16:12:18.695 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to process next mutation if one exists.
2019-01-16 16:12:18.700 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]:Persistent mutations queue is EMPTY!. Will check inMemory Queue next
2019-01-16 16:12:18.700 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]: In Memory mutations queue was EMPTY!. Nothing to process, exiting
2019-01-16 16:12:28.734 16346-16550/com.moja V/AppSyncOfflineMutationInterceptor: Thread:[15367]: processing Mutations
2019-01-16 16:12:28.735 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to take action on the mutation queue.
2019-01-16 16:12:28.736 16346-16550/com.moja V/QueueUpdateHandler: Thread:[15367]: Got message to process next mutation if one exists.
2019-01-16 16:12:28.742 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]:Persistent mutations queue is EMPTY!. Will check inMemory Queue next
2019-01-16 16:12:28.742 16346-16550/com.moja V/AppSyncOfflineMutationManager: Thread:[15367]: In Memory mutations queue was EMPTY!. Nothing to process, exiting

[scb01]

@DeMoss15
Yeah, this is logging done as part of mutation processing and is safe to ignore.

[ReemaDass]

hi , i want to format datetime to date in resolver of appsync for my requirement ..
Can anyone help me the formatting template