Cannot enqueue download task for AWS pre-signed URL object

[hsoniwork]

Describe the bug I have implemented this plugin and it works well in Android whereas on iOS I cannot see if the task has been enqueued so far or not. I have followed all the instructions and have enabled the background fetch for the project too. I am also requesting all the image permissions to save in the library.

To Reproduce Since there is no similar bug here on GitHub then my steps may not be applicable as it is too generic. I am just setting the up plugin as per the instructions. I am not sure what will be needed to resolve this issue.

Expected behavior The expected behavior is enqueue() method should return true or false if I am awaiting the call e.g. await FileDownlaoder().enqueue()

Logs

I see Starting task <task_id> and
Some timeout information

Code

//Method to generate S3 bucket URL from amplify storage. I have checked all the permissions for object access. 
Future<Map<String, dynamic>> getDownloadableUrl(
    String fileName,
  ) async {
    try {
      final result = await amplify.Amplify.Storage
          .getUrl(
            key: fileName,
            options: const amplify.StorageGetUrlOptions(
              accessLevel: amplify.StorageAccessLevel.guest,
              pluginOptions: S3GetUrlPluginOptions(
                validateObjectExistence: true,
                expiresIn: Duration(days: 1),
              ),
            ),
          )
          .result;
      Uri fileUri = Uri.parse(result.url.toString());
      Map<String, String> queryParams = {};
      fileUri.queryParameters.forEach((key, value) {
        queryParams.addEntries({key: Uri.encodeQueryComponent(value)}.entries);
      });
      return {
        'url': result.url.toString(),
        'queryParams': queryParams,
      };
    } on amplify.StorageException catch (e) {
      amplify.safePrint('Could not get a downloadable URL: ${e.message}');
      rethrow;
    }
  }

// Creating download task based on the URL and query params received from above method
final task = DownloadTask(
              taskId: fishDownloadTaskId,
              url: map['url'],
              group: "sampleGroup,
              filename:
                  "temp_file_name",
              urlQueryParameters: map['queryParams'],
              retries: 5,
              displayName: "Downloading data,
              allowPause: true,
              metaData: 'Sample test data');

var isSuccess = await FileDownloader().enqueue(task);
print(isSuccess); //prints nothing at all. Just seeing the Starting task <task_id> on log

Snapshot from Xcode

[781flyingdutchman]

Hi, thanks for raising the issue. It's a bit hard to follow as I am not familiar with S3. Can you please check out tissue #181 and see if that help solve your problem?

[hsoniwork]

Hi @781flyingdutchman,

Thank you for your response. Unfortunately, it didn't work for me. I checked the issue before logging the new one. Also, just for your information, when I say pre-signed URL, basically its the URL to an object/file on File storage on AWS. Same URL is working well for the Android app. So for the iOS I am not sure what really is causing the issue?

My logical guess says that:

• Probably some background fetch is going on but it doesn't reflect on the logs immediately. So I would ask to you whether might be this a case with my issue?
• I also checked the encoded part for the URL but then it is working on Android and also using HTTPS so we can be sure that this URL I am generating is not an invalid one.
• Probably some restrictions on the iOS to run a background fetch process on demand?

Let me know what do you think of these?

[781flyingdutchman]

Thanks, and yes if it works as intended on Android and that same code/url does not run on iOS then that is indeed strange.

In response to your questions:

• Because you see 'starting task' you are definitely in the enqueue method on the iOS native side. What is puzzling to me is that that method doesn't appear to return with either true or false (based on your description) - there's nothing in the code that tells me why that could be, so I am wondering if there is another log entry somewhere. When running this in debug mode on a simulator, can you filter the Console output on Category Downloader and share the full logs? Can you also use those logs to determine the start and end of the enqueue effort, and share the other logs messages in that period (no PII please!) to see if something happens during the enqueue operation that are not logged under 'Downloader'?
• For the URL, can you confirm that both the URL and the query parameters are properly url-encoded? Can you also share the XCode version, the Swift compiler version and the iOS platform you are running this on? There may be an issue with the recently introduced changes to iOS 17 and XCode (that caused me to insert conditional compilation), so I would also ask that you check if the code runs properly when using version 7.12.3 of the downloader (before those changes were made)
• Assuming you have followed the iOS setup instructions, background fetch should not be an issue. You could check that by downloading another (less complicated) url like https://google.com and see if it works

I have one additional question is there any indication that the task actually starts or completes? This should be visible in the Console logs in the form of many messages related to urlsession.

Let's see if the logs and these experiments offer some insight.

[hsoniwork]

Thank you for the response. Allow me tomorrow's time and I will share the required details with you soon.

[hsoniwork]

Hi @781flyingdutchman Here are the logs for [Downlaoder] in debug mode from Android Studio.

[Downloader] Starting task with id <our_unique_object_id_aws>
[Downloader] timeoutIntervalForResource = 14400 seconds
[Downloader] timeoutIntervalForRequest = 60 seconds
[Downloader] Not using proxy for any task

For URL, yes it is encoded properly and that is why it is working fine on Android without an issue.

Here is the flutter doctor summary for your reference

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.13.9, on macOS 14.0 23A344 darwin-x64, locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 15.0.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2022.3)
[✓] VS Code (version 1.85.1)
[✓] Connected device (4 available)
[✓] Network resources

I have already tried the simple URL with one of the tasks previously. It has the same issue.

Yes, as per logs, I am seeing that task is Starting but no messages for completion.

Here is the code that I have written for a task enqueue.

 try {
    var isEnqueued = await FileDownloader().enqueue(value);
     print("Enqueue $isEnqueued");
   } catch (e) {
     print(e);
   }

It is not even printing the later statement whether it got enqueued or not.

P.S.: The above logs that I have shared comes up when I schedule a task for the first time but when I try to trigger another task I see only the first line "Starting task ..." and no other logs. Not sure why.

Please let me know if any more information is needed or not.

Thank you.

[781flyingdutchman]

If it's not working for a simple URL either then I really do think it's an issue with your setup somehow. Can you 'untick' the 'Background processing' capability (it's not needed for the downloader) and compare your Info.plist with the one in the plugin example app to make sure you haven't missed anything?

[hsoniwork]

I did what you have suggested. The difference that I see in info.plist is fetch string is removed from it.

<string>fetch</string>

[hsoniwork]

@781flyingdutchman Any idea when would I get this error on my logs?

[Downloader] Failed to move file from /private/var/mobile/Containers/Data/Application/568E2C78-1A85/Library/Caches/com.apple.nsurlsessiond/Downloads/com.etournament.fishing.testflight/CFNetworkDownload_p83cJc.tmp to /var/mobile/Containers/Data/Application/568E2C78-1A85/Documents/file_name3.37_25 Dec, 2023.jpg: “CFNetworkDownload_p83cJc.tmp” couldn’t be moved to “Documents” because either the former doesn’t exist, or the folder containing the latter doesn’t exist.

[781flyingdutchman]

I did what you have suggested. The difference that I see in info.plist is fetch string is removed from it.

<string>fetch</string>

So, does it work after you made this change?

@781flyingdutchman Any idea when would I get this error on my logs?

It would be helpful to add the code that triggered this error. Based on the log, it appears you called moveToSharedStorage but the path you're moving it to doesn't seem to fit any SharedStorage destinations.

[hsoniwork]

No, it did not work after the code change. I occasionally see this log when I run the app for the first time and also trigger the first download. So not sure what is wrong with it.

I have tried the example you have shared on GitHub for this plugin. Following things I tried.

• I tried running the example on a Simulator. It works fine on it.
• When I tried copying the same method processLoadAndOpen in my code base and triggered the download then it didn't go through this line from _basedownloader.dart file. I did not get any response back from enqueue() method.

//base_downloader.dart, Line number 282 
final enqueueSuccess = await enqueue(taskToEnqueue);

What could be the reasons of the enqueue() method not returning at all?

[781flyingdutchman]

• When I tried copying the same method processLoadAndOpen in my code base and triggered the download then it didn't go through this line from _basedownloader.dart file. I did not get any response back from enqueue() method.

If you're trying to download the same file as in the sample app, then this really does suggest an issue with your setup/configuration. Have you looked at the Console? On a Mac, this is where the detailed logs of the attached simulator or device show up - Android studio only shows a subset. Perhaps there is some guidance in there as to why this error occurs.

[hsoniwork]

Yes, I tried running the app from Xcode and checked the console. But no other logs are coming up.

[jamescardona11]

I'm not sure if this is a library problem because I currently have my system to download and upload files to s3 with pre-signed url and everything works for me.

[github-actions[bot]]

This issue is stale because it has been open for 14 days with no activity.

[github-actions[bot]]

This issue was closed because it has been inactive for 7 days since being marked as stale.