[Storage] Support downloading files in background

[richardmcclellan]

The AWSS3StoragePlugin creates a TransferService, which is an Android Service. As of Android O (API 26), a Service cannot be started in the background (source), which means that transfers cannot be initiated while the app is in the background. Instead, we should use the new JobScheduler, which is allowed to run periodically in the background.

Attempts to start a transfer while in the background result in the following error:

AmplifyException {message=Something went wrong with your AWS S3 Storage list operation, cause=java.lang.IllegalStateException: Not allowed to start service Intent { cmp=com.netafim.tech_app/com.amazonaws.mobileconnectors.s3.transferutility.TransferService }: app is in background uid UidRecord{e945dd1 u0a281 TRNB bg:+1m5s172ms idle change:idle procs:1 seq(0,0,0)}, recoverySuggestion=See attached exception for more information and suggestions}
        at com.amplifyframework.storage.s3.operation.AWSS3StorageListOperation.lambda$start$0$AWSS3StorageListOperation(AWSS3StorageListOperation.java:95)
        at com.amplifyframework.storage.s3.operation.-$$Lambda$AWSS3StorageListOperation$h_rYgEkUSCQ04HohVqKR6853m80.run(Unknown Source:2)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.lang.Thread.run(Thread.java:919)
     Caused by: java.lang.IllegalStateException: Not allowed to start service Intent { cmp=com.netafim.tech_app/com.amazonaws.mobileconnectors.s3.transferutility.TransferService }: app is in background uid UidRecord{e945dd1 u0a281 TRNB bg:+1m5s172ms idle change:idle procs:1 seq(0,0,0)}
        at android.app.ContextImpl.startServiceCommon(ContextImpl.java:1616)
        at android.app.ContextImpl.startService(ContextImpl.java:1571)
        at android.content.ContextWrapper.startService(ContextWrapper.java:669)
        at com.amplifyframework.storage.s3.service.AWSS3StorageService.startServiceIfNotAlreadyStarted(AWSS3StorageService.java:226)
        at com.amplifyframework.storage.s3.service.AWSS3StorageService.listFiles(AWSS3StorageService.java:157)
        at com.amplifyframework.storage.s3.operation.AWSS3StorageListOperation.lambda$start$0$AWSS3StorageListOperation(AWSS3StorageListOperation.java:91)
        at com.amplifyframework.storage.s3.operation.-$$Lambda$AWSS3StorageListOperation$h_rYgEkUSCQ04HohVqKR6853m80.run(Unknown Source:2) 
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462) 
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 
        at java.lang.Thread.run(Thread.java:919) 

Originally reported on StackOverflow: https://stackoverflow.com/questions/65789564/failed-to-use-amplify-storage-with-a-periodic-worker

[LaurieScheepers]

Any updates on this?

[LaurieScheepers]

I have figured out a workaround for this. Please see answer at https://stackoverflow.com/questions/65789564/failed-to-use-amplify-storage-with-a-periodic-worker/71171153#71171153

[HuiSF]

Before delivering support of background download/upload, I think at least it should prevent App from crashing. This thread suggests a change to prevent the crash.

Change call of startService to startForegroundService.

https://github.com/aws-amplify/amplify-android/blob/1375235eb2d100f40f70afc8a4de8e2f77b457ab/aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/service/AWSS3StorageService.java#L249-L255

[androidcodehunter]

@HuiSF so this issue will be resolved in the next version of amplify in android right? Because it is so common in android to run the uploading tasks using Worker.

[sdhuka]

Background support for upload & download operation is available in Amplify 2.0

[github-actions[bot]]

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