Randomized non-reproducible hashes in asset bundle names

Unity Engine
1

We are currently getting familiar with addressables package in our project. Version 1.1.7.
Seems like hashes in asset bundle names are randomized and are not reproducible.
Steps to reproduce:

  1. Clean repo by running git clean -xdf && git reset --hard
  2. Do a fresh project import with iOS target
  3. Click to Build Player Content
  4. downloadablegroup_assets_all_b489b444bcd325a8957ba52060eb1e0d.bundle file is created
  5. Clean, import and build once again
  6. downloadablegroup_assets_all_311bc64f0f43adf17aae3842cf53e52d.bundle file is created

To be honest this is very annoying.

Calling BuildContentUpdate multiple times will generate a different .bundle.
Addressables + Cloud Build: Updating remote resources
2

I am fairly confident that the issue is the “import” you are doing, not addressables. There are a few importers that are non deterministic. On top of that, there are quite a few ways your project code can cause non-determinism. Custom importers in your project, hooks in the import process, or hooks in the scene build process, to name the main ones.

If you are sure it’s addressables doing something bad, please open a Unity bug with a repro project.

3

@unity_bill Thanks for the response. We are not using any custom importers or build process hooks in our project. Anyway I would like to check this myself first. Could you please tell me addressables (scriptable build pipeline?) classes where asset bundle hash is calculated so I can debug it?

4

I’ve managed to narrow down the issue to ContentBuildInterface.WriteSerializedFile() call inside AssetBundleWriteOperation class. In my case Command.serializeObjects contains 1915 objects and their serializationIndex/localIdentifierInFile/guid field do not change between fresh imports. Generated by WriteSerializedFile() call file is named CAB-3b59866ebe196603ffe6e64073b996ea.resS and is always
16527120 bytes in size. File size does not change between fresh imports. But the file contents do change between fresh imports. So looks like for the same serializeObjects list different but equal in size resS files are generated. How can I debug this futher? Maybe I can somehow dump contents for serializeObject on per-object basis?

5

As I understand via hash calculation in ArchiveAndCompressBundles.cs :
CAB-xxxx with extension resS contains raw data (e.g. texture content, geometry or animation streams, etc) because serialised objects are built into CAB-xxxx without extension.

I always meet difference in hash of texture when it’s built in different OS, but sometime hash changed even on the same build agent (with disabled unity cache server).
If you narrow down to the type of indetermined data - tell please. It’s interesting, because currently to minimize changes I must build bundles in only one build agent with local cache server enabled.:frowning:

6

Hey @unity_bill Can you please help me with this issue?

7

@unity_bill up