UnityWebRequest has no Error following CRC Mismatch

Hi,

We recently implemented CRC values instead of Version numbers for our AssetBundle versioning. The system is working ok so far but we're having a problem capturing and displaying CRC mismatch errors when they occur.

Take this simple example below. Assume the passed in CRC value is incorrect. What we're finding is that the 'test' UnityWebRequest object contains no errors following a CRC mismatch. Specifically none of the Debug.LogError statements fire if a mismatch occurs in the code below:

Code (CSharp):

1. UnityWebRequest test = UnityWebRequestAssetBundle.GetAssetBundle("http://www.oursite.com/bundle.unity3d",123456789);
2. yield return test.SendWebRequest();
3.  
4. if(!test.isDone)
5. {
6.     Debug.LogError("LOAD NOT DONE");
7. }
8.  
9. if (test.error != null)
10. {
11.     Debug.LogError("ERROR");
12. }
13.  
14. if (test.isHttpError)
15. {
16.     Debug.LogError("HTTP ERROR");
17. }
18.  
19. if (test.isNetworkError)
20. {
21.     Debug.LogError("NETWORK ERROR");
22. }
23.  

The weird part is that we do find an error in our console like this:


But it seems like the error originates from somewhere else. Ultimately, all I'm trying to do is capture mismatches when they occur so our team can easily find and fix them. Any help here would be great!

 

Actually in the example above, we are not calling DownloadHandlerAssetBundle.GetContent(). I can generate a mismatch error above without attempting to get content or access the AssetBundle.

In normal conditions calling GetContent() would be the next step to take, but I specifically created this simple example to illustrate the point that it seems the error gets thrown from another source.

 

I double confirmed this to be true. I've add a break after this code to ensure nothing else fires and I've determined specifically that it only requires these 2 lines to trigger cause the error in the console but I'm not sure how to capture the error to handle it.

Code (CSharp):

1. UnityWebRequest test = UnityWebRequestAssetBundle.GetAssetBundle("http://www.oursite.com/bundle.unity3d",123456789);
2. yield return test.SendWebRequest();

 

Ah ok thank you, you posted just as I was typing my last message!
Submitting bug report now.

 

https://fogbugz.unity3d.com/default.asp?1101142_grboh6vjncshodfr

 

Yes, this is pretty annoying, since apparently merely checking the assetbundle reference causes it to be "loaded", and will cause an error if you try to load it later unless you Unload.

Thanks for reporting, @TitanUnity

 

have you actually tested this code - warnings about the old system (WWW.LoadFromCacheOrDownload) encouraged me to overhaul my assetBundle loading, but after many hours of debugging, and constant crashing to desktop, I eventually just copied the example code directly into a new script and added it to a gameObject in an empty scene in a new project.. Even the raw test code causes an immediate fatal crash to desktop (Unity 2018.3.6f1);

void Start()
{
StartCoroutine(GetText());
}

IEnumerator GetText()
{
using (UnityWebRequest uwr = UnityWebRequestAssetBundle.GetAssetBundle("http://www.my-server.com/mybundle"))
{
yield return uwr.SendWebRequest();

if (uwr.isNetworkError || uwr.isHttpError)
{
Debug.Log(uwr.error);
}
else
{
// Get downloaded asset bundle
AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(uwr);
}
}
}

 

this is code copied verbatim from your documentation:

https://docs.unity3d.com/ScriptReference/Networking.UnityWebRequestAssetBundle.GetAssetBundle.html

it never gets to the AssetBundle content call; it crashes immediately at this line:

yield return uwr.SendWebRequest();

sometimes it succeeds, but if you point it at a bundle it doesn't like it is guaranteed to crash immediately. The only time it doesn't crash is if the URL is invalid, then you get a 404

 

it's worse than crashing - it dumps you out of Unity immediately

even trying to bypass the example code with this causes an immediate fatal crash

uint version = 0;
string url = "https://www.google.com";
UnityWebRequest uwr = new UnityWebRequest(url, UnityWebRequest.kHttpVerbGET, new DownloadHandlerAssetBundle(url, version), null);
yield return uwr.SendWebRequest();//crashes here

 

version was specified in my original reply - it the latest official release: Unity 2018.3.6f1
also running on windows 10 - the bundle is not especially relevant - it crashes long before it gets a look in but I have built bundles and loaded them successfully in the past for all platforms including windows and WebGL - this is the app I am maintaining but I am not currently attempting to load WebGL bundles

 

for clarity, your sample modified as follows causes an immediate crash to desktop

using (UnityWebRequest uwr = UnityWebRequestAssetBundle.GetAssetBundle("http://www.my-server.com/mybundle"))
{
yield return uwr.SendWebRequest();

if (uwr.isNetworkError || uwr.isHttpError)
{
Debug.Log(uwr.error);
}
else
{
// Get downloaded asset bundle
//AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(uwr);
Debug.Log("succeed");//never gets here
}
}

 

thank you for your help by the way, this is the first time I have posted a support request and someone has actually responded!

 

I promise you the problem is with UnityWebRequestAssetBundle. I had the exact same issue before with the old system (WWW.LoadFromCacheOrDownload) in that it would forcibly crash in exactly the same way but only if it encountered incompatible asset bundles. The new system crashes even when the bundles are valid so it is completely useless. I am going back to my old system for now and I have pragma'd out the warnings.. FYI this is my current working system:

public static class AssetBundleUtility
{
#pragma warning disable 0618
public static IEnumerator GetAssetBundle(string url, int version, System.Action<AssetBundle> result)
{
using (var www = WWW.LoadFromCacheOrDownload(url, version))
{
yield return www;
if (true == string.IsNullOrEmpty(www.error))
{
if (null != www.assetBundle)
{
result(www.assetBundle);
yield break;
}
}
result(null);
}
}
#pragma warning restore 0618
}

called as follows:

yield return AssetBundleUtility.GetAssetBundle(url, (int)BundleVersion.version, value => roomBundle = value);

 

all you have to do is follow the instructions in the OP. Start a new project in current release of Unity (2018.3.6f1) on a Windows10 64 machine, create a script as per the Unity example and attach it to a GameObject in the scene . Try to load any AssetBundle from anywhere on the internet (valid or otherwise) and it will crash out of Unity before it even attempts to extract the assetBundle from the data i.e.when this is invoked: SendWebRequest(). It's 100% reliable. If you pass an invalid URL it fails with a 404 as you would expect

Unity example here:

https://docs.unity3d.com/ScriptReference/Networking.UnityWebRequestAssetBundle.GetAssetBundle.html

 

I think it's important to note that if you have ever successfully loaded the AssetBundle it will continue to 'load' without problem. If you change the version number though it will immediately fail again with a crash. This is one of the problems that had me so confused. Because I had old successfully loaded AssetBundles with the old system, they were cached, so when I changed to the new system everything seemed fine at first. It was only after I tried to load new assetBundles that it crashed horribly. If you want to reproduce the problem you'll need to clear out your cached asset bundles or bump the version number

 

OK FYI I have found this is completely compatible with my old system, I have had to add an extra '0' as an argument, but I can now load AssetBundles with version without it crashing Unity.. This is a very brittle system but as long as the AssetBundles are valid and available at the URL then Unity continues functioning.. Any problem at all with the assetBundle at the location results in an immediate crash, and especially if I do not add the last '0' in the versioned loader

public static IEnumerator GetAssetBundle(string url, uint version, System.Action<AssetBundle> result)
{
using (UnityWebRequest uwr = UnityWebRequestAssetBundle.GetAssetBundle(url, version, 0))//notice the last argument
{
yield return uwr.SendWebRequest();
if (false==uwr.isNetworkError && false == uwr.isHttpError)
{
result(DownloadHandlerAssetBundle.GetContent(uwr));
yield break;
}
}
result(null);
}

 

yes I'll be happy to do this. If you would like me to email you personally I can do that. Further to this thread I think part of the problem is when some sort of corrupted / bad asset bundle has made it into the local cache. After that it doesn't seem to matter what you do with the code, it just fatally crashes out. It might be that some of the steps I have suggested are only valid in this context so I apologise if you have tried to reproduce the problem without success. As I said at the start though I do promise you that Unity just exits out without warning under certain circumstances and specifically when that function is invoked: yield return uwr.SendWebRequest(); regardless of whether the DownloadHandlerAssetBundle.GetContent(uwr) is even present in the code

 

I tried to post it to you but it ended up here: https://forum.unity.com/conversations/assetbundle-crashing-unity-editor-with-fatal-exception.520000/