Could not load System.Memory.Data when running `func start`

Question

Could not load System.Memory.Data when running `func start`

Mike Klinkhammer 20

I am suddenly having this issue when I try and run my azure functions locally. I am using azure core tools and azurite to run these functions locally using the debugger 'attach to python functions'. We have all of our connections info in my local.settings.json file but I didn't change any of these connections. I have tried uninstalling the core tools package and azurite but that did not work. When I go to where the my core tools package is located in my file explorer I can find the file it is complaining about. I can find similar threads but nothing that seems to work for me so any help would be appreciated. The only thing I can think of is some kind of package mismatch but I was able to run this successfully with the same versions and settings before the weekend.

Also worth mentioning that I am working on a virtual machine that runs windows because I using a Mac. This hasn't been an issue but worth mentioning.

Specific error here:

[2025-03-18T16:48:03.899Z] A host error has occurred during startup operation '28def80f-0277-43ff-b005-b43eddbf4f19'.

[2025-03-18T16:48:03.902Z] System.Private.CoreLib: Exception has been thrown by the target of an invocation. Microsoft.Azure.WebJobs.Extensions.Storage.Queues: Could not load file or assembly 'System.Memory.Data, Version=6.0.0.0, Culture=neutral, PublicKeyToken=abc123'. The system cannot find the file specified.
Value cannot be null. (Parameter 'provider')

[2025-03-18T16:48:03.962Z] Host startup operation has been canceled

Mike Klinkhammer 20 Reputation points

2025-03-18T22:33:15.6366667+00:00
@LeelaRajeshSayana-MSFT After messing around with the versions and different versions of the package I am able to avoid that error in favor of another. Worth mentioning that we were using npm and chocolatey versions of the package and I had to uninstall both and only install the npm one to get it to this point. I assume this is part of the issue I am having now.

[2025-03-18T22:17:26.133Z] Failed to initialize worker provider for: C:\Users\User\AppData\Roaming\npm\node_modules\azure-functions-core-tools\bin\workers\python [2025-03-18T22:17:26.136Z] Microsoft.Azure.WebJobs.Script: File DefaultWorkerPath: C:\Users\User\AppData\Roaming\npm\node_modules\azure-functions-core-tools\bin\workers\python\3.10/WINDOWS/Arm64/worker.py does not exist.

It now can't find the worker file even though I can find it in the file explorer. I tried referencing that file directly in my local.settings.json file and that didn't help. Any insight on this issue or the chocolatey vs npm packages?

Mike Klinkhammer 20

Update
I fixed the file path manually and deleted some cached files and now get this error

[2025-03-19T13:10:18.275Z] There was an error performing a read operation on the Blob Storage Secret Repository.

[2025-03-19T13:10:18.281Z] System.Net.Http: The response ended prematurely, with at least 785 additional bytes expected. (ResponseEnded).
Value cannot be null. (Parameter 'provider')

LeelaRajeshSayana-MSFT 17,521 Reputation points

2025-03-19T23:01:00.55+00:00

@Mike Klinkhammer I have reached out to you offline through a private message. Please respond to the message for additional assistance.

Accepted answer

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Mike Klinkhammer 20 Reputation points

2025-03-18T22:33:15.6366667+00:00

@LeelaRajeshSayana-MSFT After messing around with the versions and different versions of the package I am able to avoid that error in favor of another. Worth mentioning that we were using npm and chocolatey versions of the package and I had to uninstall both and only install the npm one to get it to this point. I assume this is part of the issue I am having now.

[2025-03-18T22:17:26.133Z] Failed to initialize worker provider for: C:\Users\User\AppData\Roaming\npm\node_modules\azure-functions-core-tools\bin\workers\python [2025-03-18T22:17:26.136Z] Microsoft.Azure.WebJobs.Script: File DefaultWorkerPath: C:\Users\User\AppData\Roaming\npm\node_modules\azure-functions-core-tools\bin\workers\python\3.10/WINDOWS/Arm64/worker.py does not exist.

It now can't find the worker file even though I can find it in the file explorer. I tried referencing that file directly in my local.settings.json file and that didn't help. Any insight on this issue or the chocolatey vs npm packages?
Mike Klinkhammer 20 Reputation points

2025-03-19T13:14:54.7333333+00:00

Update
I fixed the file path manually and deleted some cached files and now get this error

[2025-03-19T13:10:18.275Z] There was an error performing a read operation on the Blob Storage Secret Repository. [2025-03-19T13:10:18.281Z] System.Net.Http: The response ended prematurely, with at least 785 additional bytes expected. (ResponseEnded). Value cannot be null. (Parameter 'provider')
LeelaRajeshSayana-MSFT 17,521 Reputation points

2025-03-19T23:01:00.55+00:00

@Mike Klinkhammer I have reached out to you offline through a private message. Please respond to the message for additional assistance.

Answer 1

@Mike Klinkhammer Can you try updating the package System.Memory.Data to the latest stable version 9.0.3 and test this behavior? It could be possible that the latest version of Azure Core tools is not compatible with this version. Can you also check by creating a new project and see if you encounter this issue? If you see this behavior only in the exisitng project, it most definitely is due to the project referencing the wrong dependency. Try rebuilding the project and see if the function app points to the correct dependencies.

Please keep us posted on your findings.

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Could not load System.Memory.Data when running `func start`

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