Bug (Case 1346825) Addressables.DownloadDependenciesAsync doesn't detect error if internet drops

Unity 2019.4.20f1, Addressables 1.18.4, Android Player.

Addressables.DownloadDependenciesAsync

does not detect when the internet / Wi-Fi connection drops off while downloading.

Reproduce

1. Open attached project
2. Switch to Android build target
3. Open "Window > Asset Management > Addressables > Profiles" and activate "Editor Hosting"
4. Open "Window > Asset Management > Addressables > Groups" and click "Build > New Build > Default Build Script"
5. Click "File > Build and Run"
6. Open "Window > Asset Management > Addressables > Hosting" and enable it
7. In the running Android Player click the "Check for new content" button
8. While data is being downloaded, turn off Wi-Fi

Actual

Addressables.DownloadDependenciesAsync

never completes, even when you restore the internet / Wi-Fi connection.

Expected
The

AsyncOperationHandle.IsDone

returned by

Addressables.DownloadDependenciesAsync

equals true.
The

AsyncOperationHandle.Status

returned by

Addressables.DownloadDependenciesAsync

equals

AsyncOperationStatus.Failed

.

Notes
I say "it should resume" in the video. Forget about that, it should return an error instead.

 

I think I might have identified the issue. In AssetBundleResource, when it goes to retry a web request via BeginOperation, it never resets m_WebRequestCompletedCallbackCalled, so the subsequent success or failure of that attempt is never reported. (See the fix on line 6 of the example code).

Code (CSharp):

1.         private void BeginOperation()
2.         {
3. ...
4.             else if (loadType == LoadType.Web)
5.             {
6.                 m_WebRequestCompletedCallbackCalled = false;
7.                 var req = CreateWebRequest(m_TransformedInternalId);
8.                 req.disposeDownloadHandlerOnDispose = false;
9.  
10.                 m_WebRequestQueueOperation = WebRequestQueue.QueueRequest(req);
11.                 if (m_WebRequestQueueOperation.IsDone)
12.                 {
13.                     m_RequestOperation = m_WebRequestQueueOperation.Result;

 

Thank you for the reply.

What Addressables version do you use? I'm using 1.18.4. In Addressables 1.18.4 the

AssetBundleResource

class doesn't have a

m_WebRequestCompletedCallbackCalled

member. The related

BeginOperation

code looks also slightly different:

Code (CSharp):

1.         private void BeginOperation()
2.         {
3. ...
4.             else if (ResourceManagerConfig.ShouldPathUseWebRequest(path))
5.             {
6.                 var req = CreateWebRequest(path);
7.                 req.disposeDownloadHandlerOnDispose = false;
8.              
9.                 m_WebRequestQueueOperation = WebRequestQueue.QueueRequest(req);
10.                 if (m_WebRequestQueueOperation.IsDone)
11.                 {
12.                     m_RequestOperation = m_WebRequestQueueOperation.Result;

 

This is in `1.18.9`.

For reference, it's set as soon as it gets into the WebRequestOperationCompleted call, and used to prevent the call from being triggered multiple times. Maybe you can find the equivalent version in `1.18.4`?

Code (CSharp):

1.         private void WebRequestOperationCompleted(AsyncOperation op)
2.         {
3.             if (m_WebRequestCompletedCallbackCalled)
4.                 return;
5.  
6.             m_WebRequestCompletedCallbackCalled = true;

 

I think this retry behavior was fixed in later 1.18.* versions. Also in 1.19.4 there is now what seems to be a very useful feature of timeout based on last downloaded chunk received (how timeout is supposed to work for downloads). I haven't tested these much though (because we switched to using DownloadManager class and it does everything for us on OS-level, we just check status periodically). Also keep in mind that Addressables still doesn't have resume download functionality, which is important considering it can't download in background. In a mobile game, users WILL minimize/close the app during download and if you have bundles larger than 10mb - you are screwed

 

the same error still exit on unity 2020.3.47 with addressable 1.21.12

 

Same error on unity 2021.3.5f1 and addressables 1.19.19

 

The same error with addressable 1.21.14.

Async operation will not completed never! It's critical bug. Only reload application can helps restart async operation!
If you just start new addressable operation for this location will be returned previous broken operation. This operation executing infinity time(complete callback not called, don't change progress and download progress).

 

For reproduce this bug you need:

• use any operation: download, load or instantiate
• your bundle must be 'remote'
  
• addressables package 1.21.14
• unity version - any, but i use 2021.3.*

Steps:

• start app
• clean bundles cache(Caching.ClearCache)
• disable internet connection
• start your operation for 'remote' bundle
• BUG - addressable async operation will execute infinity time without changes(progress, callback or download state)

My assumptions about why the bug is happening:

• AssetBundleProvider has method WebRequestOperationCompleted
• this method check bool field m_RequestCompletedCallbackCalled at the start of method
• 1 reason of bug it's - retry feature don't reset this flag before call 'BeginOperation()'. Need reset flag before 'BeginOperation()'
• look at forceRetry code block (starts at 771 line in AssetBundleProvider.cs)
• Code (CSharp):

  1. if (m_Retries == 0 && uwrResult.ShouldRetryDownloadError())
  2. {
  3.     Debug.LogFormat(message);
  4.     BeginOperation();
  5.     m_Retries++; //Will prevent us from entering an infinite loop of retrying if retry count is 0
  6.     forcedRetry = true;
  7. }
• 2 reason of bug it's - 'm_Retries++' executed after 'BeginOperation'. Need increment counter before 'BeginOperation', else code will again recurse enter to 'forceRetry' code block.

How fix BUG(tested in Rider debugger with evaluator):

• before (AssetBundleProvider.cs:771)
  
  Code (CSharp):

  1. if (m_Retries == 0 && uwrResult.ShouldRetryDownloadError())
  2. {
  3.     Debug.LogFormat(message);
  4.     BeginOperation();
  5.     m_Retries++; //Will prevent us from entering an infinite loop of retrying if retry count is 0
  6.     forcedRetry = true;
  7. }
• after (AssetBundleProvider.cs:771)
  
  Code (CSharp):

  1. if (m_Retries == 0 && uwrResult.ShouldRetryDownloadError())
  2. {
  3.     Debug.LogFormat(message);
  4.     m_Retries++; //Will prevent us from entering an infinite loop of retrying if retry count is 0
  5.     m_RequestCompletedCallbackCalled = false;
  6.     BeginOperation();
  7.     forcedRetry = true;
  8. }

 

Also need fix 'm_RequestCompletedCallbackCalled' flag here:

• before (AssetBundleProvider.cs:781)
  
  Code (CSharp):

  1. if (!forcedRetry)
  2. {
  3.     if (m_Retries < m_Options.RetryCount && uwrResult.ShouldRetryDownloadError())
  4.     {
  5.         m_Retries++;
  6.         Debug.LogFormat(message);
  7.         BeginOperation();
  8.     }
  9. .....
• after(AssetBundleProvider.cs:781)
  
  Code (CSharp):

  1. if (!forcedRetry)
  2. {
  3.     if (m_Retries < m_Options.RetryCount && uwrResult.ShouldRetryDownloadError())
  4.     {
  5.         m_Retries++;
  6.         m_RequestCompletedCallbackCalled = false;
  7.         Debug.LogFormat(message);
  8.         BeginOperation();
  9.     }
  10. .....